Rework caching and use it inside the query engine. (#553) r=emily

This puts caching in mentat_db, adds a reverse lookup capability for
unique attributes, and populates bidirectional caches with a single
SQL cursor walk.

Differentiate between begin_read and begin_uncached_read.

Note that we still allow toggling within InProgress, because there might be
transient local state that makes starting a new transaction impossible.

core/src/cache.rs

@@ -0,0 +1,32 @@
+// Copyright 2018 Mozilla
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
+// this file except in compliance with the License. You may obtain a copy of the
+// License at http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software distributed
+// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+// CONDITIONS OF ANY KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations under the License.
+
+/// Cache traits.
+
+use std::collections::{
+    BTreeSet,
+};
+
+use ::{
+    Entid,
+    Schema,
+    TypedValue,
+};
+
+pub trait CachedAttributes {
+    fn is_attribute_cached_reverse(&self, entid: Entid) -> bool;
+    fn is_attribute_cached_forward(&self, entid: Entid) -> bool;
+    fn get_values_for_entid(&self, schema: &Schema, attribute: Entid, entid: Entid) -> Option<&Vec<TypedValue>>;
+    fn get_value_for_entid(&self, schema: &Schema, attribute: Entid, entid: Entid) -> Option<&TypedValue>;
+
+    /// Reverse lookup.
+    fn get_entid_for_value(&self, attribute: Entid, value: &TypedValue) -> Option<Entid>;
+    fn get_entids_for_value(&self, attribute: Entid, value: &TypedValue) -> Option<&BTreeSet<Entid>>;
+}

core/src/lib.rs

@@ -23,6 +23,7 @@ extern crate serde_derive;
 extern crate edn;
 
 pub mod values;
+mod cache;
 
 use std::collections::{
     BTreeMap,
@@ -50,6 +51,8 @@ pub use edn::{
     Utc,
 };
 
+pub use cache::CachedAttributes;
+
 /// Core types defining a Mentat knowledge base.
 
 /// Represents one entid in the entid space.

db/src/cache.rs

@@ -8,92 +8,557 @@
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
 
-use std::cmp::Ord;
+use std::collections::{
-use std::collections::BTreeMap;
+    BTreeMap,
-use std::fmt::Debug;
+    BTreeSet,
+};
+
+use std::iter::Peekable;
 
 use rusqlite;
 
-use errors::{
-    Result
-};
-use db::{
-    TypedSQLValue,
-};
 use mentat_core::{
+    CachedAttributes,
     Entid,
+    HasSchema,
+    Schema,
     TypedValue,
 };
 
+use db::{
+    TypedSQLValue,
+};
+
+use errors::{
+    ErrorKind,
+    Result,
+};
+
+pub type Aev = (Entid, Entid, TypedValue);
+
+fn row_to_aev(row: &rusqlite::Row) -> Aev {
+    let a: Entid = row.get(0);
+    let e: Entid = row.get(1);
+    let value_type_tag: i32 = row.get(3);
+    let v = TypedValue::from_sql_value_pair(row.get(2), value_type_tag).map(|x| x).unwrap();
+    (a, e, v)
+}
+
 pub type CacheMap<K, V> = BTreeMap<K, V>;
 
-pub trait ValueProvider<K, V>: Clone {
+pub struct AevRows<'conn> {
-    fn fetch_values<'sqlite>(&mut self, sqlite: &'sqlite rusqlite::Connection) -> Result<CacheMap<K, V>>;
+    rows: rusqlite::MappedRows<'conn, fn(&rusqlite::Row) -> Aev>,
 }
 
-pub trait Cacheable {
+/// Unwrap the Result from MappedRows. We could also use this opportunity to map_err it, but
-    type Key;
+/// for now it's convenient to avoid error handling.
-    type Value;
+impl<'conn> Iterator for AevRows<'conn> {
-
+    type Item = Aev;
-    fn cache_values<'sqlite>(&mut self, sqlite: &'sqlite rusqlite::Connection) -> Result<()>;
+    fn next(&mut self) -> Option<Aev> {
-    fn get(&self, key: &Self::Key) -> Option<&Self::Value>;
+        self.rows
-}
+            .next()
-
+            .map(|row_result| row_result.expect("All database contents should be representable"))
-#[derive(Clone)]
-pub struct EagerCache<K, V, VP> where K: Ord, VP: ValueProvider<K, V> {
-    pub cache: CacheMap<K, V>,
-    value_provider: VP,
-}
-
-impl<K, V, VP> EagerCache<K, V, VP> where K: Ord, VP: ValueProvider<K, V> {
-    pub fn new(value_provider: VP) -> Self  {
-        EagerCache {
-            cache: CacheMap::new(),
-            value_provider: value_provider,
-        }
     }
 }
 
-impl<K, V, VP> Cacheable for EagerCache<K, V, VP>
+// The behavior of the cache is different for different kinds of attributes:
-    where K: Ord + Clone + Debug + ::std::hash::Hash,
+// - cardinality/one doesn't need a vec
-          V: Clone,
+// - unique/* should have a bijective mapping (reverse lookup)
-          VP: ValueProvider<K, V> {
-    type Key = K;
-    type Value = V;
 
-    fn cache_values<'sqlite>(&mut self, sqlite: &'sqlite rusqlite::Connection) -> Result<()> {
+trait CardinalityOneCache {
-        // fetch results and add to cache
+    fn clear(&mut self);
-        self.cache = self.value_provider.fetch_values(sqlite)?;
+    fn set(&mut self, e: Entid, v: TypedValue);
+    fn get(&self, e: Entid) -> Option<&TypedValue>;
+}
+
+trait CardinalityManyCache {
+    fn clear(&mut self);
+    fn acc(&mut self, e: Entid, v: TypedValue);
+    fn set(&mut self, e: Entid, vs: Vec<TypedValue>);
+    fn get(&self, e: Entid) -> Option<&Vec<TypedValue>>;
+}
+
+#[derive(Debug, Default)]
+struct SingleValAttributeCache {
+    attr: Entid,
+    e_v: CacheMap<Entid, TypedValue>,
+}
+
+impl CardinalityOneCache for SingleValAttributeCache {
+    fn clear(&mut self) {
+        self.e_v.clear();
+    }
+
+    fn set(&mut self, e: Entid, v: TypedValue) {
+        self.e_v.insert(e, v);
+    }
+
+    fn get(&self, e: Entid) -> Option<&TypedValue> {
+        self.e_v.get(&e)
+    }
+}
+
+#[derive(Debug, Default)]
+struct MultiValAttributeCache {
+    attr: Entid,
+    e_vs: CacheMap<Entid, Vec<TypedValue>>,
+}
+
+impl CardinalityManyCache for MultiValAttributeCache {
+    fn clear(&mut self) {
+        self.e_vs.clear();
+    }
+
+    fn acc(&mut self, e: Entid, v: TypedValue) {
+        self.e_vs.entry(e).or_insert(vec![]).push(v)
+    }
+
+    fn set(&mut self, e: Entid, vs: Vec<TypedValue>) {
+        self.e_vs.insert(e, vs);
+    }
+
+    fn get(&self, e: Entid) -> Option<&Vec<TypedValue>> {
+        self.e_vs.get(&e)
+    }
+}
+
+#[derive(Debug, Default)]
+struct UniqueReverseAttributeCache {
+    attr: Entid,
+    v_e: CacheMap<TypedValue, Entid>,
+}
+
+impl UniqueReverseAttributeCache {
+    fn clear(&mut self) {
+        self.v_e.clear();
+    }
+
+    fn set(&mut self, e: Entid, v: TypedValue) {
+        self.v_e.insert(v, e);
+    }
+
+    fn get_e(&self, v: &TypedValue) -> Option<Entid> {
+        self.v_e.get(v).cloned()
+    }
+}
+
+#[derive(Debug, Default)]
+struct NonUniqueReverseAttributeCache {
+    attr: Entid,
+    v_es: CacheMap<TypedValue, BTreeSet<Entid>>,
+}
+
+impl NonUniqueReverseAttributeCache {
+    fn clear(&mut self) {
+        self.v_es.clear();
+    }
+
+    fn acc(&mut self, e: Entid, v: TypedValue) {
+        self.v_es.entry(v).or_insert(BTreeSet::new()).insert(e);
+    }
+
+    fn get_es(&self, v: &TypedValue) -> Option<&BTreeSet<Entid>> {
+        self.v_es.get(v)
+    }
+}
+
+#[derive(Debug, Default)]
+pub struct AttributeCaches {
+    reverse_cached_attributes: BTreeSet<Entid>,
+    forward_cached_attributes: BTreeSet<Entid>,
+
+    single_vals: BTreeMap<Entid, SingleValAttributeCache>,
+    multi_vals: BTreeMap<Entid, MultiValAttributeCache>,
+    unique_reverse: BTreeMap<Entid, UniqueReverseAttributeCache>,
+    non_unique_reverse: BTreeMap<Entid, NonUniqueReverseAttributeCache>,
+}
+
+fn with_aev_iter<F, I>(a: Entid, iter: &mut Peekable<I>, mut f: F)
+where I: Iterator<Item=Aev>,
+      F: FnMut(Entid, TypedValue) {
+    let check = Some(a);
+    while iter.peek().map(|&(a, _, _)| a) == check {
+        let (_, e, v) = iter.next().unwrap();
+        f(e, v);
+    }
+}
+
+fn accumulate_single_val_evs_forward<I, C>(a: Entid, f: &mut C, iter: &mut Peekable<I>) where I: Iterator<Item=Aev>, C: CardinalityOneCache {
+    with_aev_iter(a, iter, |e, v| f.set(e, v))
+}
+
+fn accumulate_multi_val_evs_forward<I, C>(a: Entid, f: &mut C, iter: &mut Peekable<I>) where I: Iterator<Item=Aev>, C: CardinalityManyCache {
+    with_aev_iter(a, iter, |e, v| f.acc(e, v))
+}
+
+fn accumulate_unique_evs_reverse<I>(a: Entid, r: &mut UniqueReverseAttributeCache, iter: &mut Peekable<I>) where I: Iterator<Item=Aev> {
+    with_aev_iter(a, iter, |e, v| r.set(e, v))
+}
+
+fn accumulate_non_unique_evs_reverse<I>(a: Entid, r: &mut NonUniqueReverseAttributeCache, iter: &mut Peekable<I>) where I: Iterator<Item=Aev> {
+    with_aev_iter(a, iter, |e, v| r.acc(e, v))
+}
+
+fn accumulate_single_val_unique_evs_both<I, C>(a: Entid, f: &mut C, r: &mut UniqueReverseAttributeCache, iter: &mut Peekable<I>) where I: Iterator<Item=Aev>, C: CardinalityOneCache {
+    with_aev_iter(a, iter, |e, v| {
+        f.set(e, v.clone());
+        r.set(e, v);
+    })
+}
+
+fn accumulate_multi_val_unique_evs_both<I, C>(a: Entid, f: &mut C, r: &mut UniqueReverseAttributeCache, iter: &mut Peekable<I>) where I: Iterator<Item=Aev>, C: CardinalityManyCache {
+    with_aev_iter(a, iter, |e, v| {
+        f.acc(e, v.clone());
+        r.set(e, v);
+    })
+}
+
+fn accumulate_single_val_non_unique_evs_both<I, C>(a: Entid, f: &mut C, r: &mut NonUniqueReverseAttributeCache, iter: &mut Peekable<I>) where I: Iterator<Item=Aev>, C: CardinalityOneCache {
+    with_aev_iter(a, iter, |e, v| {
+        f.set(e, v.clone());
+        r.acc(e, v);
+    })
+}
+
+fn accumulate_multi_val_non_unique_evs_both<I, C>(a: Entid, f: &mut C, r: &mut NonUniqueReverseAttributeCache, iter: &mut Peekable<I>) where I: Iterator<Item=Aev>, C: CardinalityManyCache {
+    with_aev_iter(a, iter, |e, v| {
+        f.acc(e, v.clone());
+        r.acc(e, v);
+    })
+}
+
+// TODO: if an entity or attribute is ever renumbered, the cache will need to be rebuilt.
+impl AttributeCaches {
+    //
+    // These function names are brief and local.
+    // f = forward; r = reverse; both = both forward and reverse.
+    // s = single-val; m = multi-val.
+    // u = unique; nu = non-unique.
+    // c = cache.
+    #[inline]
+    fn fsc(&mut self, a: Entid) -> &mut SingleValAttributeCache {
+        self.single_vals
+            .entry(a)
+            .or_insert_with(Default::default)
+    }
+
+    #[inline]
+    fn fmc(&mut self, a: Entid) -> &mut MultiValAttributeCache {
+        self.multi_vals
+            .entry(a)
+            .or_insert_with(Default::default)
+    }
+
+    #[inline]
+    fn ruc(&mut self, a: Entid) -> &mut UniqueReverseAttributeCache {
+        self.unique_reverse
+            .entry(a)
+            .or_insert_with(Default::default)
+    }
+
+    #[inline]
+    fn rnuc(&mut self, a: Entid) -> &mut NonUniqueReverseAttributeCache {
+        self.non_unique_reverse
+            .entry(a)
+            .or_insert_with(Default::default)
+    }
+
+    #[inline]
+    fn both_s_u<'r>(&'r mut self, a: Entid) -> (&'r mut SingleValAttributeCache, &'r mut UniqueReverseAttributeCache) {
+        (self.single_vals.entry(a).or_insert_with(Default::default),
+         self.unique_reverse.entry(a).or_insert_with(Default::default))
+    }
+
+    #[inline]
+    fn both_m_u<'r>(&'r mut self, a: Entid) -> (&'r mut MultiValAttributeCache, &'r mut UniqueReverseAttributeCache) {
+        (self.multi_vals.entry(a).or_insert_with(Default::default),
+         self.unique_reverse.entry(a).or_insert_with(Default::default))
+    }
+
+    #[inline]
+    fn both_s_nu<'r>(&'r mut self, a: Entid) -> (&'r mut SingleValAttributeCache, &'r mut NonUniqueReverseAttributeCache) {
+        (self.single_vals.entry(a).or_insert_with(Default::default),
+         self.non_unique_reverse.entry(a).or_insert_with(Default::default))
+    }
+
+    #[inline]
+    fn both_m_nu<'r>(&'r mut self, a: Entid) -> (&'r mut MultiValAttributeCache, &'r mut NonUniqueReverseAttributeCache) {
+        (self.multi_vals.entry(a).or_insert_with(Default::default),
+         self.non_unique_reverse.entry(a).or_insert_with(Default::default))
+    }
+
+    // Process rows in `iter` that all share an attribute with the first. Leaves the iterator
+    // advanced to the first non-matching row.
+    fn accumulate_evs<I>(&mut self, schema: &Schema, iter: &mut Peekable<I>, replace_a: bool) where I: Iterator<Item=Aev> {
+        if let Some(&(a, _, _)) = iter.peek() {
+            if let Some(attribute) = schema.attribute_for_entid(a) {
+                let forward = self.is_attribute_cached_forward(a);
+                let reverse = self.is_attribute_cached_reverse(a);
+                let multi = attribute.multival;
+                let unique = attribute.unique.is_some();
+                match (forward, reverse, multi, unique) {
+                    (true, true, true, true) => {
+                        let (f, r) = self.both_m_u(a);
+                        if replace_a {
+                            f.clear();
+                            r.clear();
+                        }
+                        accumulate_multi_val_unique_evs_both(a, f, r, iter);
+                    },
+                    (true, true, true, false) => {
+                        let (f, r) = self.both_m_nu(a);
+                        if replace_a {
+                            f.clear();
+                            r.clear();
+                        }
+                        accumulate_multi_val_non_unique_evs_both(a, f, r, iter);
+                    },
+                    (true, true, false, true) => {
+                        let (f, r) = self.both_s_u(a);
+                        if replace_a {
+                            f.clear();
+                            r.clear();
+                        }
+                        accumulate_single_val_unique_evs_both(a, f, r, iter);
+                    },
+                    (true, true, false, false) => {
+                        let (f, r) = self.both_s_nu(a);
+                        if replace_a {
+                            f.clear();
+                            r.clear();
+                        }
+                        accumulate_single_val_non_unique_evs_both(a, f, r, iter);
+                    },
+                    (true, false, true, _) => {
+                        let f = self.fmc(a);
+                        if replace_a {
+                            f.clear();
+                        }
+                        accumulate_multi_val_evs_forward(a, f, iter)
+                    },
+                    (true, false, false, _) => {
+                        let f = self.fsc(a);
+                        if replace_a {
+                            f.clear();
+                        }
+                        accumulate_single_val_evs_forward(a, f, iter)
+                    },
+                    (false, true, _, true) => {
+                        let r = self.ruc(a);
+                        if replace_a {
+                            r.clear();
+                        }
+                        accumulate_unique_evs_reverse(a, r, iter);
+                    },
+                    (false, true, _, false) => {
+                        let r = self.rnuc(a);
+                        if replace_a {
+                            r.clear();
+                        }
+                        accumulate_non_unique_evs_reverse(a, r, iter);
+                    },
+                    (false, false, _, _) => {
+                        unreachable!();           // Must be cached in at least one direction!
+                    },
+                }
+            }
+        }
+    }
+
+    fn add_to_cache<I>(&mut self, schema: &Schema, mut iter: Peekable<I>, replace_a: bool) -> Result<()> where I: Iterator<Item=Aev> {
+        while iter.peek().is_some() {
+            self.accumulate_evs(schema, &mut iter, replace_a);
+        }
         Ok(())
     }
 
-    fn get(&self, key: &Self::Key) -> Option<&Self::Value> {
+    fn clear_cache(&mut self) {
-        self.cache.get(&key)
+        self.single_vals.clear();
+        self.multi_vals.clear();
+        self.unique_reverse.clear();
+        self.non_unique_reverse.clear();
+    }
+
+    fn unregister_all_attributes(&mut self) {
+        self.reverse_cached_attributes.clear();
+        self.forward_cached_attributes.clear();
+        self.clear_cache();
+    }
+
+    pub fn unregister_attribute<U>(&mut self, attribute: U)
+    where U: Into<Entid> {
+        let a = attribute.into();
+        self.reverse_cached_attributes.remove(&a);
+        self.forward_cached_attributes.remove(&a);
+        self.single_vals.remove(&a);
+        self.multi_vals.remove(&a);
+        self.unique_reverse.remove(&a);
+        self.non_unique_reverse.remove(&a);
     }
 }
 
-#[derive(Clone)]
+impl CachedAttributes for AttributeCaches {
-pub struct AttributeValueProvider {
+    fn get_values_for_entid(&self, schema: &Schema, attribute: Entid, entid: Entid) -> Option<&Vec<TypedValue>> {
-    pub attribute: Entid,
+        self.values_pairs(schema, attribute)
+            .and_then(|c| c.get(&entid))
+    }
+
+    fn get_value_for_entid(&self, schema: &Schema, attribute: Entid, entid: Entid) -> Option<&TypedValue> {
+        self.value_pairs(schema, attribute)
+            .and_then(|c| c.get(&entid))
+    }
+
+    fn is_attribute_cached_reverse(&self, attribute: Entid) -> bool {
+        self.reverse_cached_attributes.contains(&attribute)
+    }
+
+    fn is_attribute_cached_forward(&self, attribute: Entid) -> bool {
+        self.forward_cached_attributes.contains(&attribute)
+    }
+
+    fn get_entid_for_value(&self, attribute: Entid, value: &TypedValue) -> Option<Entid> {
+        if self.is_attribute_cached_reverse(attribute) {
+            self.unique_reverse.get(&attribute).and_then(|c| c.get_e(value))
+        } else {
+            None
+        }
+    }
+
+    fn get_entids_for_value(&self, attribute: Entid, value: &TypedValue) -> Option<&BTreeSet<Entid>> {
+        if self.is_attribute_cached_reverse(attribute) {
+            self.non_unique_reverse.get(&attribute).and_then(|c| c.get_es(value))
+        } else {
+            None
+        }
+    }
 }
 
-impl ValueProvider<Entid, Vec<TypedValue>> for AttributeValueProvider {
+impl AttributeCaches {
-    fn fetch_values<'sqlite>(&mut self, sqlite: &'sqlite rusqlite::Connection) -> Result<CacheMap<Entid, Vec<TypedValue>>> {
+    fn values_pairs<U>(&self, schema: &Schema, attribute: U) -> Option<&BTreeMap<Entid, Vec<TypedValue>>>
-        let sql = "SELECT e, v, value_type_tag FROM datoms WHERE a = ? ORDER BY e ASC";
+    where U: Into<Entid> {
+        let attribute = attribute.into();
+        schema.attribute_for_entid(attribute)
+              .and_then(|attr|
+                if attr.multival {
+                    self.multi_vals
+                        .get(&attribute)
+                        .map(|c| &c.e_vs)
+                } else {
+                    None
+                })
+    }
+
+    fn value_pairs<U>(&self, schema: &Schema, attribute: U) -> Option<&CacheMap<Entid, TypedValue>>
+    where U: Into<Entid> {
+        let attribute = attribute.into();
+        schema.attribute_for_entid(attribute)
+              .and_then(|attr|
+                if attr.multival {
+                    None
+                } else {
+                    self.single_vals
+                        .get(&attribute)
+                        .map(|c| &c.e_v)
+                })
+    }
+}
+
+#[derive(Debug, Default)]
+pub struct SQLiteAttributeCache {
+    inner: AttributeCaches,
+}
+
+impl SQLiteAttributeCache {
+    pub fn register_forward<U>(&mut self, schema: &Schema, sqlite: &rusqlite::Connection, attribute: U) -> Result<()>
+    where U: Into<Entid> {
+        let a = attribute.into();
+
+        // The attribute must exist!
+        let _ = schema.attribute_for_entid(a).ok_or_else(|| ErrorKind::UnknownAttribute(a))?;
+        self.inner.forward_cached_attributes.insert(a);
+        self.repopulate(schema, sqlite, a)
+    }
+
+    pub fn register_reverse<U>(&mut self, schema: &Schema, sqlite: &rusqlite::Connection, attribute: U) -> Result<()>
+    where U: Into<Entid> {
+        let a = attribute.into();
+
+        // The attribute must exist!
+        let _ = schema.attribute_for_entid(a).ok_or_else(|| ErrorKind::UnknownAttribute(a))?;
+
+        self.inner.reverse_cached_attributes.insert(a);
+        self.repopulate(schema, sqlite, a)
+    }
+
+    pub fn register<U>(&mut self, schema: &Schema, sqlite: &rusqlite::Connection, attribute: U) -> Result<()>
+    where U: Into<Entid> {
+        let a = attribute.into();
+
+        // TODO: reverse-index unique by default?
+
+        self.inner.forward_cached_attributes.insert(a);
+        self.inner.reverse_cached_attributes.insert(a);
+        self.repopulate(schema, sqlite, a)
+    }
+
+    fn repopulate(&mut self, schema: &Schema, sqlite: &rusqlite::Connection, attribute: Entid) -> Result<()> {
+        let sql = "SELECT a, e, v, value_type_tag FROM datoms WHERE a = ? ORDER BY a ASC, e ASC";
+        let args: Vec<&rusqlite::types::ToSql> = vec![&attribute];
         let mut stmt = sqlite.prepare(sql)?;
-        let value_iter = stmt.query_map(&[&self.attribute], |row| {
+        let rows = stmt.query_map(&args, row_to_aev as fn(&rusqlite::Row) -> Aev)?;
-            let entid: Entid = row.get(0);
+        let aevs = AevRows {
-            let value_type_tag: i32 = row.get(2);
+            rows: rows,
-            let value = TypedValue::from_sql_value_pair(row.get(1), value_type_tag).map(|x| x).unwrap();
+        };
-            (entid, value)
+        self.inner.add_to_cache(schema, aevs.peekable(), true)?;
-        }).map_err(|e| e.into());
+        Ok(())
-        value_iter.map(|v| {
+    }
-            v.fold(CacheMap::new(), |mut map, row| {
+
-                let _ = row.map(|r| {
+    pub fn unregister<U>(&mut self, attribute: U)
-                    map.entry(r.0).or_insert(vec![]).push(r.1);
+    where U: Into<Entid> {
-                });
+        self.inner.unregister_attribute(attribute);
-                map
+    }
-            })
+
-        })
+    pub fn unregister_all(&mut self) {
+        self.inner.unregister_all_attributes();
+    }
+}
+
+impl CachedAttributes for SQLiteAttributeCache {
+    fn get_values_for_entid(&self, schema: &Schema, attribute: Entid, entid: Entid) -> Option<&Vec<TypedValue>> {
+        self.inner.get_values_for_entid(schema, attribute, entid)
+    }
+
+    fn get_value_for_entid(&self, schema: &Schema, attribute: Entid, entid: Entid) -> Option<&TypedValue> {
+        self.inner.get_value_for_entid(schema, attribute, entid)
+    }
+
+    fn is_attribute_cached_reverse(&self, attribute: Entid) -> bool {
+        self.inner.is_attribute_cached_reverse(attribute)
+    }
+
+    fn is_attribute_cached_forward(&self, attribute: Entid) -> bool {
+        self.inner.is_attribute_cached_forward(attribute)
+    }
+
+    fn get_entids_for_value(&self, attribute: Entid, value: &TypedValue) -> Option<&BTreeSet<Entid>> {
+        self.inner.get_entids_for_value(attribute, value)
+    }
+
+    fn get_entid_for_value(&self, attribute: Entid, value: &TypedValue) -> Option<Entid> {
+        self.inner.get_entid_for_value(attribute, value)
+    }
+}
+
+impl SQLiteAttributeCache {
+    /// Intended for use from tests.
+    pub fn values_pairs<U>(&self, schema: &Schema, attribute: U) -> Option<&BTreeMap<Entid, Vec<TypedValue>>>
+    where U: Into<Entid> {
+        self.inner.values_pairs(schema, attribute)
+    }
+
+    /// Intended for use from tests.
+    pub fn value_pairs<U>(&self, schema: &Schema, attribute: U) -> Option<&BTreeMap<Entid, TypedValue>>
+    where U: Into<Entid> {
+        self.inner.value_pairs(schema, attribute)
     }
 }

db/src/db.rs

@@ -916,7 +916,8 @@ impl MentatStoring for rusqlite::Connection {
 
             // First, insert all fulltext string values.
             // `fts_params` reference computed values in `block`.
-            let fts_params: Vec<&ToSql> = block.iter()
+            let fts_params: Vec<&ToSql> =
+                block.iter()
                      .filter(|&&(ref _e, ref _a, ref value, ref _value_type_tag, _added, ref _flags, ref _searchid)| {
                          value.is_some()
                      })

db/src/errors.rs

@@ -87,5 +87,15 @@ error_chain! {
             description("conflicting datoms in tx")
             display("conflicting datoms in tx")
         }
+
+        UnknownAttribute(attr: Entid) {
+            description("unknown attribute")
+            display("unknown attribute for entid: {}", attr)
+        }
+
+        CannotCacheNonUniqueAttributeInReverse(attr: Entid) {
+            description("cannot reverse-cache non-unique attribute")
+            display("cannot reverse-cache non-unique attribute: {}", attr)
+        }
     }
 }

query-algebrizer/src/clauses/fulltext.rs

@@ -10,7 +10,6 @@
 
 use mentat_core::{
     HasSchema,
-    Schema,
     TypedValue,
     ValueType,
 };
@@ -48,9 +47,11 @@ use types::{
     SourceAlias,
 };
 
+use Known;
+
 impl ConjoiningClauses {
     #[allow(unused_variables)]
-    pub fn apply_fulltext<'s>(&mut self, schema: &'s Schema, where_fn: WhereFn) -> Result<()> {
+    pub fn apply_fulltext(&mut self, known: Known, where_fn: WhereFn) -> Result<()> {
         if where_fn.args.len() != 3 {
             bail!(ErrorKind::InvalidNumberOfArguments(where_fn.operator.clone(), where_fn.args.len(), 3));
         }
@@ -96,6 +97,8 @@ impl ConjoiningClauses {
             _ => bail!(ErrorKind::InvalidArgument(where_fn.operator.clone(), "source variable".into(), 0)),
         }
 
+        let schema = known.schema;
+
         // TODO: accept placeholder and set of attributes.  Alternately, consider putting the search
         // term before the attribute arguments and collect the (variadic) attributes into a set.
         // let a: Entid  = self.resolve_attribute_argument(&where_fn.operator, 1, args.next().unwrap())?;
@@ -130,7 +133,7 @@ impl ConjoiningClauses {
         if !attribute.fulltext {
             // We can never get results from a non-fulltext attribute!
             println!("Can't run fulltext on non-fulltext attribute {}.", a);
-            self.mark_known_empty(EmptyBecause::InvalidAttributeEntid(a));
+            self.mark_known_empty(EmptyBecause::NonFulltextAttribute(a));
             return Ok(());
         }
 
@@ -258,6 +261,7 @@ mod testing {
 
     use mentat_core::{
         Attribute,
+        Schema,
         ValueType,
     };
 
@@ -294,8 +298,10 @@ mod testing {
             ..Default::default()
         });
 
+        let known = Known::for_schema(&schema);
+
         let op = PlainSymbol::new("fulltext");
-        cc.apply_fulltext(&schema, WhereFn {
+        cc.apply_fulltext(known, WhereFn {
             operator: op,
             args: vec![
                 FnArg::SrcVar(SrcVar::DefaultSrc),
@@ -353,7 +359,7 @@ mod testing {
 
         let mut cc = ConjoiningClauses::default();
         let op = PlainSymbol::new("fulltext");
-        cc.apply_fulltext(&schema, WhereFn {
+        cc.apply_fulltext(known, WhereFn {
             operator: op,
             args: vec![
                 FnArg::SrcVar(SrcVar::DefaultSrc),

query-algebrizer/src/clauses/ground.rs

@@ -43,6 +43,8 @@ use types::{
     VariableColumn,
 };
 
+use Known;
+
 impl ConjoiningClauses {
     /// Take a relation: a matrix of values which will successively bind to named variables of
     /// the provided types.
@@ -113,7 +115,7 @@ impl ConjoiningClauses {
         Ok(())
     }
 
-    pub fn apply_ground<'s>(&mut self, schema: &'s Schema, where_fn: WhereFn) -> Result<()> {
+    pub fn apply_ground(&mut self, known: Known, where_fn: WhereFn) -> Result<()> {
         if where_fn.args.len() != 1 {
             bail!(ErrorKind::InvalidNumberOfArguments(where_fn.operator.clone(), where_fn.args.len(), 1));
         }
@@ -130,6 +132,8 @@ impl ConjoiningClauses {
             bail!(ErrorKind::InvalidBinding(where_fn.operator.clone(), BindingError::RepeatedBoundVariable));
         }
 
+        let schema = known.schema;
+
         // Scalar and tuple bindings are a little special: because there's only one value,
         // we can immediately substitute the value as a known value in the CC, additionally
         // generating a WHERE clause if columns have already been bound.
@@ -350,10 +354,12 @@ mod testing {
             ..Default::default()
         });
 
+        let known = Known::for_schema(&schema);
+
         // It's awkward enough to write these expansions that we give the details for the simplest
         // case only.  See the tests of the translator for more extensive (albeit looser) coverage.
         let op = PlainSymbol::new("ground");
-        cc.apply_ground(&schema, WhereFn {
+        cc.apply_ground(known, WhereFn {
             operator: op,
             args: vec![
                 FnArg::EntidOrInteger(10),

query-algebrizer/src/clauses/mod.rs

@@ -13,9 +13,12 @@ use std::cmp;
 use std::collections::{
     BTreeMap,
     BTreeSet,
+    VecDeque,
 };
 
-use std::collections::btree_map::Entry;
+use std::collections::btree_map::{
+    Entry,
+};
 
 use std::fmt::{
     Debug,
@@ -37,14 +40,15 @@ use mentat_core::counter::RcCounter;
 
 use mentat_query::{
     NamespacedKeyword,
-    NonIntegerConstant,
-    Pattern,
-    PatternNonValuePlace,
-    PatternValuePlace,
     Variable,
     WhereClause,
 };
 
+#[cfg(test)]
+use mentat_query::{
+    PatternNonValuePlace,
+};
+
 use errors::{
     Error,
     ErrorKind,
@@ -59,7 +63,11 @@ use types::{
     DatomsColumn,
     DatomsTable,
     EmptyBecause,
+    EvolvedNonValuePlace,
+    EvolvedPattern,
+    EvolvedValuePlace,
     FulltextColumn,
+    PlaceOrEmpty,
     QualifiedAlias,
     QueryValue,
     SourceAlias,
@@ -85,6 +93,8 @@ use validate::{
 
 pub use self::inputs::QueryInputs;
 
+use Known;
+
 // We do this a lot for errors.
 trait RcCloned<T> {
     fn cloned(&self) -> T;
@@ -146,6 +156,8 @@ impl<K: Clone + Ord, V: Clone> Intersection<K> for BTreeMap<K, V> {
     }
 }
 
+type VariableBindings = BTreeMap<Variable, TypedValue>;
+
 /// A `ConjoiningClauses` (CC) is a collection of clauses that are combined with `JOIN`.
 /// The topmost form in a query is a `ConjoiningClauses`.
 ///
@@ -205,7 +217,7 @@ pub struct ConjoiningClauses {
     ///
     /// and for `?val` provide `TypedValue::String("foo".to_string())`, the query will be known at
     /// algebrizing time to be empty.
-    value_bindings: BTreeMap<Variable, TypedValue>,
+    value_bindings: VariableBindings,
 
     /// A map from var to type. Whenever a var maps unambiguously to two different types, it cannot
     /// yield results, so we don't represent that case here. If a var isn't present in the map, it
@@ -535,6 +547,23 @@ impl ConjoiningClauses {
         self.narrow_types_for_var(variable, ValueTypeSet::of_numeric_types());
     }
 
+    pub fn can_constrain_var_to_type(&self, var: &Variable, this_type: ValueType) -> Option<EmptyBecause> {
+        self.can_constrain_var_to_types(var, ValueTypeSet::of_one(this_type))
+    }
+
+    fn can_constrain_var_to_types(&self, var: &Variable, these_types: ValueTypeSet) -> Option<EmptyBecause> {
+        if let Some(existing) = self.known_types.get(var) {
+            if existing.intersection(&these_types).is_empty() {
+                return Some(EmptyBecause::TypeMismatch {
+                    var: var.clone(),
+                    existing: existing.clone(),
+                    desired: these_types,
+                });
+            }
+        }
+        None
+    }
+
     /// Constrains the var if there's no existing type.
     /// Marks as known-empty if it's impossible for this type to apply because there's a conflicting
     /// type already known.
@@ -673,17 +702,17 @@ impl ConjoiningClauses {
     }
 
     /// Ensure that the given place has the correct types to be a tx-id.
-    fn constrain_to_tx(&mut self, tx: &PatternNonValuePlace) {
+    fn constrain_to_tx(&mut self, tx: &EvolvedNonValuePlace) {
         self.constrain_to_ref(tx);
     }
 
     /// Ensure that the given place can be an entity, and is congruent with existing types.
     /// This is used for `entity` and `attribute` places in a pattern.
-    fn constrain_to_ref(&mut self, value: &PatternNonValuePlace) {
+    fn constrain_to_ref(&mut self, value: &EvolvedNonValuePlace) {
         // If it's a variable, record that it has the right type.
         // Ident or attribute resolution errors (the only other check we need to do) will be done
         // by the caller.
-        if let &PatternNonValuePlace::Variable(ref v) = value {
+        if let &EvolvedNonValuePlace::Variable(ref v) = value {
             self.constrain_var_to_type(v.clone(), ValueType::Ref)
         }
     }
@@ -705,17 +734,17 @@ impl ConjoiningClauses {
         schema.get_entid(&ident)
     }
 
-    fn table_for_attribute_and_value<'s, 'a>(&self, attribute: &'s Attribute, value: &'a PatternValuePlace) -> ::std::result::Result<DatomsTable, EmptyBecause> {
+    fn table_for_attribute_and_value<'s, 'a>(&self, attribute: &'s Attribute, value: &'a EvolvedValuePlace) -> ::std::result::Result<DatomsTable, EmptyBecause> {
         if attribute.fulltext {
             match value {
-                &PatternValuePlace::Placeholder =>
+                &EvolvedValuePlace::Placeholder =>
                     Ok(DatomsTable::Datoms),            // We don't need the value.
 
                 // TODO: an existing non-string binding can cause this pattern to fail.
-                &PatternValuePlace::Variable(_) =>
+                &EvolvedValuePlace::Variable(_) =>
                     Ok(DatomsTable::AllDatoms),
 
-                &PatternValuePlace::Constant(NonIntegerConstant::Text(_)) =>
+                &EvolvedValuePlace::Value(TypedValue::String(_)) =>
                     Ok(DatomsTable::AllDatoms),
 
                 _ => {
@@ -729,7 +758,7 @@ impl ConjoiningClauses {
         }
     }
 
-    fn table_for_unknown_attribute<'s, 'a>(&self, value: &'a PatternValuePlace) -> ::std::result::Result<DatomsTable, EmptyBecause> {
+    fn table_for_unknown_attribute<'s, 'a>(&self, value: &'a EvolvedValuePlace) -> ::std::result::Result<DatomsTable, EmptyBecause> {
         // If the value is known to be non-textual, we can simply use the regular datoms
         // table (TODO: and exclude on `index_fulltext`!).
         //
@@ -742,7 +771,7 @@ impl ConjoiningClauses {
             match value {
                 // TODO: see if the variable is projected, aggregated, or compared elsewhere in
                 // the query. If it's not, we don't need to use all_datoms here.
-                &PatternValuePlace::Variable(ref v) => {
+                &EvolvedValuePlace::Variable(ref v) => {
                     // If `required_types` and `known_types` don't exclude strings,
                     // we need to query `all_datoms`.
                     if self.required_types.get(v).map_or(true, |s| s.contains(ValueType::String)) &&
@@ -752,7 +781,7 @@ impl ConjoiningClauses {
                         DatomsTable::Datoms
                     }
                 }
-                &PatternValuePlace::Constant(NonIntegerConstant::Text(_)) =>
+                &EvolvedValuePlace::Value(TypedValue::String(_)) =>
                     DatomsTable::AllDatoms,
                 _ =>
                     DatomsTable::Datoms,
@@ -763,21 +792,17 @@ impl ConjoiningClauses {
     /// If the attribute input or value binding doesn't name an attribute, or doesn't name an
     /// attribute that is congruent with the supplied value, we return an `EmptyBecause`.
     /// The caller is responsible for marking the CC as known-empty if this is a fatal failure.
-    fn table_for_places<'s, 'a>(&self, schema: &'s Schema, attribute: &'a PatternNonValuePlace, value: &'a PatternValuePlace) -> ::std::result::Result<DatomsTable, EmptyBecause> {
+    fn table_for_places<'s, 'a>(&self, schema: &'s Schema, attribute: &'a EvolvedNonValuePlace, value: &'a EvolvedValuePlace) -> ::std::result::Result<DatomsTable, EmptyBecause> {
         match attribute {
-            &PatternNonValuePlace::Ident(ref kw) =>
+            &EvolvedNonValuePlace::Entid(id) =>
-                schema.attribute_for_ident(kw)
-                      .ok_or_else(|| EmptyBecause::InvalidAttributeIdent(kw.cloned()))
-                      .and_then(|(attribute, _entid)| self.table_for_attribute_and_value(attribute, value)),
-            &PatternNonValuePlace::Entid(id) =>
                 schema.attribute_for_entid(id)
                       .ok_or_else(|| EmptyBecause::InvalidAttributeEntid(id))
                       .and_then(|attribute| self.table_for_attribute_and_value(attribute, value)),
             // TODO: In a prepared context, defer this decision until a second algebrizing phase.
             // #278.
-            &PatternNonValuePlace::Placeholder =>
+            &EvolvedNonValuePlace::Placeholder =>
                 self.table_for_unknown_attribute(value),
-            &PatternNonValuePlace::Variable(ref v) => {
+            &EvolvedNonValuePlace::Variable(ref v) => {
                 // See if we have a binding for the variable.
                 match self.bound_value(v) {
                     // TODO: In a prepared context, defer this decision until a second algebrizing phase.
@@ -786,7 +811,7 @@ impl ConjoiningClauses {
                         self.table_for_unknown_attribute(value),
                     Some(TypedValue::Ref(id)) =>
                         // Recurse: it's easy.
-                        self.table_for_places(schema, &PatternNonValuePlace::Entid(id), value),
+                        self.table_for_places(schema, &EvolvedNonValuePlace::Entid(id), value),
                     Some(TypedValue::Keyword(ref kw)) =>
                         // Don't recurse: avoid needing to clone the keyword.
                         schema.attribute_for_ident(kw)
@@ -815,7 +840,7 @@ impl ConjoiningClauses {
     /// This is a mutating method because it mutates the aliaser function!
     /// Note that if this function decides that a pattern cannot match, it will flip
     /// `empty_because`.
-    fn alias_table<'s, 'a>(&mut self, schema: &'s Schema, pattern: &'a Pattern) -> Option<SourceAlias> {
+    fn alias_table<'s, 'a>(&mut self, schema: &'s Schema, pattern: &'a EvolvedPattern) -> Option<SourceAlias> {
         self.table_for_places(schema, &pattern.attribute, &pattern.value)
             .map_err(|reason| {
                 self.mark_known_empty(reason);
@@ -833,25 +858,22 @@ impl ConjoiningClauses {
         }
     }
 
-    fn get_attribute<'s, 'a>(&self, schema: &'s Schema, pattern: &'a Pattern) -> Option<&'s Attribute> {
+    fn get_attribute<'s, 'a>(&self, schema: &'s Schema, pattern: &'a EvolvedPattern) -> Option<&'s Attribute> {
         match pattern.attribute {
-            PatternNonValuePlace::Entid(id) =>
+            EvolvedNonValuePlace::Entid(id) =>
                 // We know this one is known if the attribute lookup succeeds…
                 schema.attribute_for_entid(id),
-            PatternNonValuePlace::Ident(ref kw) =>
+            EvolvedNonValuePlace::Variable(ref var) =>
-                schema.attribute_for_ident(kw).map(|(a, _id)| a),
-            PatternNonValuePlace::Variable(ref var) =>
                 // If the pattern has a variable, we've already determined that the binding -- if
                 // any -- is acceptable and yields a table. Here, simply look to see if it names
                 // an attribute so we can find out the type.
                 self.value_bindings.get(var)
                                    .and_then(|val| self.get_attribute_for_value(schema, val)),
-            _ =>
+            EvolvedNonValuePlace::Placeholder => None,
-                None,
         }
     }
 
-    fn get_value_type<'s, 'a>(&self, schema: &'s Schema, pattern: &'a Pattern) -> Option<ValueType> {
+    fn get_value_type<'s, 'a>(&self, schema: &'s Schema, pattern: &'a EvolvedPattern) -> Option<ValueType> {
         self.get_attribute(schema, pattern).map(|a| a.value_type)
     }
 }
@@ -984,43 +1006,83 @@ impl ConjoiningClauses {
 }
 
 impl ConjoiningClauses {
-    pub fn apply_clauses(&mut self, schema: &Schema, where_clauses: Vec<WhereClause>) -> Result<()> {
+    fn apply_evolved_patterns(&mut self, known: Known, mut patterns: VecDeque<EvolvedPattern>) -> Result<()> {
+        while let Some(pattern) = patterns.pop_front() {
+            match self.evolve_pattern(known, pattern) {
+                PlaceOrEmpty::Place(re_evolved) => self.apply_pattern(known, re_evolved),
+                PlaceOrEmpty::Empty(because) => {
+                    self.mark_known_empty(because);
+                    patterns.clear();
+                },
+            }
+        }
+        Ok(())
+    }
+
+    pub fn apply_clauses(&mut self, known: Known, where_clauses: Vec<WhereClause>) -> Result<()> {
         // We apply (top level) type predicates first as an optimization.
         for clause in where_clauses.iter() {
             if let &WhereClause::TypeAnnotation(ref anno) = clause {
                 self.apply_type_anno(anno)?;
             }
         }
+
         // Then we apply everything else.
+        // Note that we collect contiguous runs of patterns so that we can evolve them
+        // together to take advantage of mutual partial evaluation.
+        let mut remaining = where_clauses.len();
+        let mut patterns: VecDeque<EvolvedPattern> = VecDeque::with_capacity(remaining);
         for clause in where_clauses {
+            remaining -= 1;
             if let &WhereClause::TypeAnnotation(_) = &clause {
                 continue;
             }
-            self.apply_clause(schema, clause)?;
+            match clause {
+                WhereClause::Pattern(p) => {
+                    match self.make_evolved_pattern(known, p) {
+                        PlaceOrEmpty::Place(evolved) => patterns.push_back(evolved),
+                        PlaceOrEmpty::Empty(because) => {
+                            self.mark_known_empty(because);
+                            return Ok(());
                         }
-        Ok(())
                     }
+                },
+                _ => {
+                    if !patterns.is_empty() {
+                        self.apply_evolved_patterns(known, patterns)?;
+                        patterns = VecDeque::with_capacity(remaining);
+                    }
+                    self.apply_clause(known, clause)?;
+                },
+            }
+        }
+        self.apply_evolved_patterns(known, patterns)
+    }
+
     // This is here, rather than in `lib.rs`, because it's recursive: `or` can contain `or`,
     // and so on.
-    pub fn apply_clause(&mut self, schema: &Schema, where_clause: WhereClause) -> Result<()> {
+    pub fn apply_clause(&mut self, known: Known, where_clause: WhereClause) -> Result<()> {
         match where_clause {
             WhereClause::Pattern(p) => {
-                self.apply_pattern(schema, p);
+                match self.make_evolved_pattern(known, p) {
+                    PlaceOrEmpty::Place(evolved) => self.apply_pattern(known, evolved),
+                    PlaceOrEmpty::Empty(because) => self.mark_known_empty(because),
+                }
                 Ok(())
             },
             WhereClause::Pred(p) => {
-                self.apply_predicate(schema, p)
+                self.apply_predicate(known, p)
             },
             WhereClause::WhereFn(f) => {
-                self.apply_where_fn(schema, f)
+                self.apply_where_fn(known, f)
             },
             WhereClause::OrJoin(o) => {
                 validate_or_join(&o)?;
-                self.apply_or_join(schema, o)
+                self.apply_or_join(known, o)
             },
             WhereClause::NotJoin(n) => {
                 validate_not_join(&n)?;
-                self.apply_not_join(schema, n)
+                self.apply_not_join(known, n)
             },
             WhereClause::TypeAnnotation(anno) => {
                 self.apply_type_anno(&anno)

query-algebrizer/src/clauses/not.rs

@@ -8,8 +8,6 @@
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
 
-use mentat_core::Schema;
-
 use mentat_query::{
     ContainsVariables,
     NotJoin,
@@ -28,8 +26,10 @@ use types::{
     ComputedTable,
 };
 
+use Known;
+
 impl ConjoiningClauses {
-    pub fn apply_not_join(&mut self, schema: &Schema, not_join: NotJoin) -> Result<()> {
+    pub fn apply_not_join(&mut self, known: Known, not_join: NotJoin) -> Result<()> {
         let unified = match not_join.unify_vars {
             UnifyVars::Implicit => not_join.collect_mentioned_variables(),
             UnifyVars::Explicit(vs) => vs,
@@ -49,7 +49,7 @@ impl ConjoiningClauses {
             }
         }
 
-        template.apply_clauses(&schema, not_join.clauses)?;
+        template.apply_clauses(known, not_join.clauses)?;
 
         if template.is_known_empty() {
             return Ok(());
@@ -70,6 +70,12 @@ impl ConjoiningClauses {
             return Ok(());
         }
 
+        // If we don't impose any constraints on the output, we might as well
+        // not exist.
+        if template.wheres.is_empty() {
+            return Ok(());
+        }
+
         let subquery = ComputedTable::Subquery(template);
 
         self.wheres.add_intersection(ColumnConstraint::NotExists(subquery));
@@ -133,13 +139,15 @@ mod testing {
     };
 
     fn alg(schema: &Schema, input: &str) -> ConjoiningClauses {
+        let known = Known::for_schema(schema);
         let parsed = parse_find_string(input).expect("parse failed");
-        algebrize(schema.into(), parsed).expect("algebrize failed").cc
+        algebrize(known, parsed).expect("algebrize failed").cc
     }
 
     fn alg_with_inputs(schema: &Schema, input: &str, inputs: QueryInputs) -> ConjoiningClauses {
+        let known = Known::for_schema(schema);
         let parsed = parse_find_string(input).expect("parse failed");
-        algebrize_with_inputs(schema.into(), parsed, 0, inputs).expect("algebrize failed").cc
+        algebrize_with_inputs(known, parsed, 0, inputs).expect("algebrize failed").cc
     }
 
     fn prepopulated_schema() -> Schema {
@@ -292,7 +300,7 @@ mod testing {
         let age = QueryValue::Entid(68);
 
         let john = QueryValue::TypedValue(TypedValue::typed_string("John"));
-        let eleven = QueryValue::PrimitiveLong(11);
+        let eleven = QueryValue::TypedValue(TypedValue::Long(11));
 
         let mut subquery = ConjoiningClauses::default();
         subquery.from = vec![SourceAlias(DatomsTable::Datoms, d3)];
@@ -541,12 +549,13 @@ mod testing {
     #[test]
     fn test_unbound_var_fails() {
         let schema = prepopulated_schema();
+        let known = Known::for_schema(&schema);
         let query = r#"
         [:find ?x
          :in ?y
          :where (not [?x :foo/knows ?y])]"#;
         let parsed = parse_find_string(query).expect("parse failed");
-        let err = algebrize(&schema, parsed).err();
+        let err = algebrize(known, parsed).err();
         assert!(err.is_some());
          match err.unwrap() {
             Error(ErrorKind::UnboundVariable(var), _) => { assert_eq!(var, PlainSymbol("?x".to_string())); },

query-algebrizer/src/clauses/or.rs

@@ -15,7 +15,6 @@ use std::collections::{
 };
 
 use mentat_core::{
-    Schema,
     ValueTypeSet,
 };
 
@@ -46,11 +45,15 @@ use types::{
     ComputedTable,
     DatomsTable,
     EmptyBecause,
+    EvolvedPattern,
+    PlaceOrEmpty,
     QualifiedAlias,
     SourceAlias,
     VariableColumn,
 };
 
+use Known;
+
 /// Return true if both left and right are the same variable or both are non-variable.
 fn _simply_matches_place(left: &PatternNonValuePlace, right: &PatternNonValuePlace) -> bool {
     match (left, right) {
@@ -88,21 +91,21 @@ pub enum DeconstructedOrJoin {
 
 /// Application of `or`. Note that this is recursive!
 impl ConjoiningClauses {
-    fn apply_or_where_clause(&mut self, schema: &Schema, clause: OrWhereClause) -> Result<()> {
+    fn apply_or_where_clause(&mut self, known: Known, clause: OrWhereClause) -> Result<()> {
         match clause {
-            OrWhereClause::Clause(clause) => self.apply_clause(schema, clause),
+            OrWhereClause::Clause(clause) => self.apply_clause(known, clause),
 
             // A query might be:
             // [:find ?x :where (or (and [?x _ 5] [?x :foo/bar 7]))]
             // which is equivalent to dropping the `or` _and_ the `and`!
             OrWhereClause::And(clauses) => {
-                self.apply_clauses(schema, clauses)?;
+                self.apply_clauses(known, clauses)?;
                 Ok(())
             },
         }
     }
 
-    pub fn apply_or_join(&mut self, schema: &Schema, mut or_join: OrJoin) -> Result<()> {
+    pub fn apply_or_join(&mut self, known: Known, mut or_join: OrJoin) -> Result<()> {
         // Simple optimization. Empty `or` clauses disappear. Unit `or` clauses
         // are equivalent to just the inner clause.
 
@@ -113,7 +116,7 @@ impl ConjoiningClauses {
             0 => Ok(()),
             1 if or_join.is_fully_unified() => {
                 let clause = or_join.clauses.pop().expect("there's a clause");
-                self.apply_or_where_clause(schema, clause)
+                self.apply_or_where_clause(known, clause)
             },
             // Either there's only one clause pattern, and it's not fully unified, or we
             // have multiple clauses.
@@ -122,7 +125,7 @@ impl ConjoiningClauses {
             // Notably, this clause might be an `and`, making this a complex pattern, so we can't
             // necessarily rewrite it in place.
             // In the latter case, we still need to do a bit more work.
-            _ => self.apply_non_trivial_or_join(schema, or_join),
+            _ => self.apply_non_trivial_or_join(known, or_join),
         }
     }
 
@@ -147,7 +150,7 @@ impl ConjoiningClauses {
     /// - No patterns can match: the enclosing CC is known-empty.
     /// - Some patterns can't match: they are discarded.
     /// - Only one pattern can match: the `or` can be simplified away.
-    fn deconstruct_or_join(&self, schema: &Schema, or_join: OrJoin) -> DeconstructedOrJoin {
+    fn deconstruct_or_join(&self, known: Known, or_join: OrJoin) -> DeconstructedOrJoin {
         // If we have explicit non-maximal unify-vars, we *can't* simply run this as a
         // single pattern --
         // ```
@@ -172,7 +175,7 @@ impl ConjoiningClauses {
             // It's safe to simply 'leak' the entire clause, because we know every var in it is
             // supposed to unify with the enclosing form.
             1 => DeconstructedOrJoin::Unit(or_join.clauses.into_iter().next().unwrap()),
-            _ => self._deconstruct_or_join(schema, or_join),
+            _ => self._deconstruct_or_join(known, or_join),
         }
     }
 
@@ -183,7 +186,7 @@ impl ConjoiningClauses {
     ///
     /// See the description of `deconstruct_or_join` for more details. This method expects
     /// to be called _only_ by `deconstruct_or_join`.
-    fn _deconstruct_or_join(&self, schema: &Schema, or_join: OrJoin) -> DeconstructedOrJoin {
+    fn _deconstruct_or_join(&self, known: Known, or_join: OrJoin) -> DeconstructedOrJoin {
         // Preconditions enforced by `deconstruct_or_join`.
         // Note that a fully unified explicit `or-join` can arrive here, and might leave as
         // an implicit `or`.
@@ -215,8 +218,19 @@ impl ConjoiningClauses {
                 // Compute the table for the pattern. If we can't figure one out, it means
                 // the pattern cannot succeed; we drop it.
                 // Inside an `or` it's not a failure for a pattern to be unable to match, which
-                // manifests as a table being unable to be found.
+                use self::PlaceOrEmpty::*;
-                let table = self.table_for_places(schema, &p.attribute, &p.value);
+                let table = match self.make_evolved_attribute(&known, p.attribute.clone()) {
+                    Place((aaa, value_type)) => {
+                        match self.make_evolved_value(&known, value_type, p.value.clone()) {
+                            Place(v) => {
+                                self.table_for_places(known.schema, &aaa, &v)
+                            },
+                            Empty(e) => Err(e),
+                        }
+                    },
+                    Empty(e) => Err(e),
+                };
+
                 match table {
                     Err(e) => {
                         empty_because = Some(e);
@@ -290,8 +304,8 @@ impl ConjoiningClauses {
         }
     }
 
-    fn apply_non_trivial_or_join(&mut self, schema: &Schema, or_join: OrJoin) -> Result<()> {
+    fn apply_non_trivial_or_join(&mut self, known: Known, or_join: OrJoin) -> Result<()> {
-        match self.deconstruct_or_join(schema, or_join) {
+        match self.deconstruct_or_join(known, or_join) {
             DeconstructedOrJoin::KnownSuccess => {
                 // The pattern came to us empty -- `(or)`. Do nothing.
                 Ok(())
@@ -304,22 +318,29 @@ impl ConjoiningClauses {
             },
             DeconstructedOrJoin::Unit(clause) => {
                 // There was only one clause. We're unifying all variables, so we can just apply here.
-                self.apply_or_where_clause(schema, clause)
+                self.apply_or_where_clause(known, clause)
             },
             DeconstructedOrJoin::UnitPattern(pattern) => {
                 // Same, but simpler.
-                self.apply_pattern(schema, pattern);
+                match self.make_evolved_pattern(known, pattern) {
+                    PlaceOrEmpty::Empty(e) => {
+                        self.mark_known_empty(e);
+                    },
+                    PlaceOrEmpty::Place(pattern) => {
+                        self.apply_pattern(known, pattern);
+                    },
+                };
                 Ok(())
             },
             DeconstructedOrJoin::Simple(patterns, mentioned_vars) => {
                 // Hooray! Fully unified and plain ol' patterns that all use the same table.
                 // Go right ahead and produce a set of constraint alternations that we can collect,
                 // using a single table alias.
-                self.apply_simple_or_join(schema, patterns, mentioned_vars)
+                self.apply_simple_or_join(known, patterns, mentioned_vars)
             },
             DeconstructedOrJoin::Complex(or_join) => {
                 // Do this the hard way.
-                self.apply_complex_or_join(schema, or_join)
+                self.apply_complex_or_join(known, or_join)
             },
         }
     }
@@ -353,7 +374,7 @@ impl ConjoiningClauses {
     /// ```
     ///
     fn apply_simple_or_join(&mut self,
-                            schema: &Schema,
+                            known: Known,
                             patterns: Vec<Pattern>,
                             mentioned_vars: BTreeSet<Variable>)
                             -> Result<()> {
@@ -363,6 +384,17 @@ impl ConjoiningClauses {
 
         assert!(patterns.len() >= 2);
 
+        let patterns: Vec<EvolvedPattern> = patterns.into_iter().filter_map(|pattern| {
+            match self.make_evolved_pattern(known, pattern) {
+                PlaceOrEmpty::Empty(_e) => {
+                    // Never mind.
+                    None
+                },
+                PlaceOrEmpty::Place(p) => Some(p),
+            }
+        }).collect();
+
+
         // Begin by building a base CC that we'll use to produce constraints from each pattern.
         // Populate this base CC with whatever variables are already known from the CC to which
         // we're applying this `or`.
@@ -373,7 +405,7 @@ impl ConjoiningClauses {
 
         // We expect this to always work: if it doesn't, it means we should never have got to this
         // point.
-        let source_alias = self.alias_table(schema, &patterns[0]).expect("couldn't get table");
+        let source_alias = self.alias_table(known.schema, &patterns[0]).expect("couldn't get table");
 
         // This is where we'll collect everything we eventually add to the destination CC.
         let mut folded = ConjoiningClauses::default();
@@ -405,7 +437,7 @@ impl ConjoiningClauses {
                         .map(|pattern| {
                             let mut receptacle = template.make_receptacle();
                             println!("Applying pattern with attribute {:?}", pattern.attribute);
-                            receptacle.apply_pattern_clause_for_alias(schema, &pattern, &source_alias);
+                            receptacle.apply_pattern_clause_for_alias(known, &pattern, &source_alias);
                             receptacle
                         })
                         .peekable();
@@ -543,7 +575,7 @@ impl ConjoiningClauses {
     ///
     /// Note that a top-level standalone `or` doesn't really need to be aliased, but
     /// it shouldn't do any harm.
-    fn apply_complex_or_join(&mut self, schema: &Schema, or_join: OrJoin) -> Result<()> {
+    fn apply_complex_or_join(&mut self, known: Known, or_join: OrJoin) -> Result<()> {
         // N.B., a solitary pattern here *cannot* be simply applied to the enclosing CC. We don't
         // want to join all the vars, and indeed if it were safe to do so, we wouldn't have ended up
         // in this function!
@@ -562,10 +594,10 @@ impl ConjoiningClauses {
             let mut receptacle = template.make_receptacle();
             match clause {
                 OrWhereClause::And(clauses) => {
-                    receptacle.apply_clauses(&schema, clauses)?;
+                    receptacle.apply_clauses(known, clauses)?;
                 },
                 OrWhereClause::Clause(clause) => {
-                    receptacle.apply_clause(&schema, clause)?;
+                    receptacle.apply_clause(known, clause)?;
                 },
             }
             if receptacle.is_known_empty() {
@@ -670,6 +702,7 @@ impl ConjoiningClauses {
         let alias = self.next_alias_for_table(table);
 
         // Stitch the computed table into column_bindings, so we get cross-linking.
+        let schema = known.schema;
         for var in var_associations.into_iter() {
             self.bind_column_to_var(schema, alias.clone(), VariableColumn::Variable(var.clone()), var);
         }
@@ -726,6 +759,7 @@ mod testing {
 
     use mentat_core::{
         Attribute,
+        Schema,
         TypedValue,
         ValueType,
     };
@@ -759,16 +793,16 @@ mod testing {
         algebrize_with_counter,
     };
 
-    fn alg(schema: &Schema, input: &str) -> ConjoiningClauses {
+    fn alg(known: Known, input: &str) -> ConjoiningClauses {
         let parsed = parse_find_string(input).expect("parse failed");
-        algebrize(schema.into(), parsed).expect("algebrize failed").cc
+        algebrize(known, parsed).expect("algebrize failed").cc
     }
 
     /// Algebrize with a starting counter, so we can compare inner queries by algebrizing a
     /// simpler version.
-    fn alg_c(schema: &Schema, counter: usize, input: &str) -> ConjoiningClauses {
+    fn alg_c(known: Known, counter: usize, input: &str) -> ConjoiningClauses {
         let parsed = parse_find_string(input).expect("parse failed");
-        algebrize_with_counter(schema.into(), parsed, counter).expect("algebrize failed").cc
+        algebrize_with_counter(known, parsed, counter).expect("algebrize failed").cc
     }
 
     fn compare_ccs(left: ConjoiningClauses, right: ConjoiningClauses) {
@@ -815,40 +849,43 @@ mod testing {
     #[test]
     fn test_schema_based_failure() {
         let schema = Schema::default();
+        let known = Known::for_schema(&schema);
         let query = r#"
             [:find ?x
              :where (or [?x :foo/nope1 "John"]
                         [?x :foo/nope2 "Ámbar"]
                         [?x :foo/nope3 "Daphne"])]"#;
-        let cc = alg(&schema, query);
+        let cc = alg(known, query);
         assert!(cc.is_known_empty());
-        assert_eq!(cc.empty_because, Some(EmptyBecause::InvalidAttributeIdent(NamespacedKeyword::new("foo", "nope3"))));
+        assert_eq!(cc.empty_because, Some(EmptyBecause::UnresolvedIdent(NamespacedKeyword::new("foo", "nope3"))));
     }
 
     /// Test that if only one of the attributes in an `or` resolves, it's equivalent to a simple query.
     #[test]
     fn test_only_one_arm_succeeds() {
         let schema = prepopulated_schema();
+        let known = Known::for_schema(&schema);
         let query = r#"
             [:find ?x
              :where (or [?x :foo/nope "John"]
                         [?x :foo/parent "Ámbar"]
                         [?x :foo/nope "Daphne"])]"#;
-        let cc = alg(&schema, query);
+        let cc = alg(known, query);
         assert!(!cc.is_known_empty());
-        compare_ccs(cc, alg(&schema, r#"[:find ?x :where [?x :foo/parent "Ámbar"]]"#));
+        compare_ccs(cc, alg(known, r#"[:find ?x :where [?x :foo/parent "Ámbar"]]"#));
     }
 
     // Simple alternation.
     #[test]
     fn test_simple_alternation() {
         let schema = prepopulated_schema();
+        let known = Known::for_schema(&schema);
         let query = r#"
             [:find ?x
              :where (or [?x :foo/knows "John"]
                         [?x :foo/parent "Ámbar"]
                         [?x :foo/knows "Daphne"])]"#;
-        let cc = alg(&schema, query);
+        let cc = alg(known, query);
         let vx = Variable::from_valid_name("?x");
         let d0 = "datoms00".to_string();
         let d0e = QualifiedAlias::new(d0.clone(), DatomsColumn::Entity);
@@ -882,6 +919,7 @@ mod testing {
     #[test]
     fn test_alternation_with_pattern() {
         let schema = prepopulated_schema();
+        let known = Known::for_schema(&schema);
         let query = r#"
             [:find [?x ?name]
              :where
@@ -889,7 +927,7 @@ mod testing {
              (or [?x :foo/knows "John"]
                  [?x :foo/parent "Ámbar"]
                  [?x :foo/knows "Daphne"])]"#;
-        let cc = alg(&schema, query);
+        let cc = alg(known, query);
         let vx = Variable::from_valid_name("?x");
         let d0 = "datoms00".to_string();
         let d1 = "datoms01".to_string();
@@ -932,6 +970,7 @@ mod testing {
     #[test]
     fn test_alternation_with_pattern_and_predicate() {
         let schema = prepopulated_schema();
+        let known = Known::for_schema(&schema);
         let query = r#"
             [:find ?x ?age
              :where
@@ -939,7 +978,7 @@ mod testing {
              [[< ?age 30]]
              (or [?x :foo/knows "John"]
                  [?x :foo/knows "Daphne"])]"#;
-        let cc = alg(&schema, query);
+        let cc = alg(known, query);
         let vx = Variable::from_valid_name("?x");
         let d0 = "datoms00".to_string();
         let d1 = "datoms01".to_string();
@@ -985,10 +1024,11 @@ mod testing {
     #[test]
     fn test_unit_or_join_doesnt_flatten() {
         let schema = prepopulated_schema();
+        let known = Known::for_schema(&schema);
         let query = r#"[:find ?x
                         :where [?x :foo/knows ?y]
                                (or-join [?x] [?x :foo/parent ?y])]"#;
-        let cc = alg(&schema, query);
+        let cc = alg(known, query);
         let vx = Variable::from_valid_name("?x");
         let vy = Variable::from_valid_name("?y");
         let d0 = "datoms00".to_string();
@@ -1020,28 +1060,30 @@ mod testing {
     #[test]
     fn test_unit_or_does_flatten() {
         let schema = prepopulated_schema();
+        let known = Known::for_schema(&schema);
         let or_query =   r#"[:find ?x
                              :where [?x :foo/knows ?y]
                                     (or [?x :foo/parent ?y])]"#;
         let flat_query = r#"[:find ?x
                              :where [?x :foo/knows ?y]
                                     [?x :foo/parent ?y]]"#;
-        compare_ccs(alg(&schema, or_query),
+        compare_ccs(alg(known, or_query),
-                    alg(&schema, flat_query));
+                    alg(known, flat_query));
     }
 
     // Elision of `and`.
     #[test]
     fn test_unit_or_and_does_flatten() {
         let schema = prepopulated_schema();
+        let known = Known::for_schema(&schema);
         let or_query =   r#"[:find ?x
                              :where (or (and [?x :foo/parent ?y]
                                              [?x :foo/age 7]))]"#;
         let flat_query =   r#"[:find ?x
                                :where [?x :foo/parent ?y]
                                       [?x :foo/age 7]]"#;
-        compare_ccs(alg(&schema, or_query),
+        compare_ccs(alg(known, or_query),
-                    alg(&schema, flat_query));
+                    alg(known, flat_query));
     }
 
     // Alternation with `and`.
@@ -1054,12 +1096,13 @@ mod testing {
     #[test]
     fn test_alternation_with_and() {
         let schema = prepopulated_schema();
+        let known = Known::for_schema(&schema);
         let query = r#"
             [:find ?x
              :where (or (and [?x :foo/knows "John"]
                              [?x :foo/parent "Ámbar"])
                         [?x :foo/knows "Daphne"])]"#;
-        let cc = alg(&schema, query);
+        let cc = alg(known, query);
         let mut tables = cc.computed_tables.into_iter();
         match (tables.next(), tables.next()) {
             (Some(ComputedTable::Union { projection, type_extraction, arms }), None) => {
@@ -1069,12 +1112,12 @@ mod testing {
                 let mut arms = arms.into_iter();
                 match (arms.next(), arms.next(), arms.next()) {
                     (Some(and), Some(pattern), None) => {
-                        let expected_and = alg_c(&schema,
+                        let expected_and = alg_c(known,
                                                  0,  // The first pattern to be processed.
                                                  r#"[:find ?x :where [?x :foo/knows "John"] [?x :foo/parent "Ámbar"]]"#);
                         compare_ccs(and, expected_and);
 
-                        let expected_pattern = alg_c(&schema,
+                        let expected_pattern = alg_c(known,
                                                      2,      // Two aliases taken by the other arm.
                                                      r#"[:find ?x :where [?x :foo/knows "Daphne"]]"#);
                         compare_ccs(pattern, expected_pattern);
@@ -1093,6 +1136,7 @@ mod testing {
     #[test]
     fn test_type_based_or_pruning() {
         let schema = prepopulated_schema();
+        let known = Known::for_schema(&schema);
         // This simplifies to:
         // [:find ?x
         //  :where [?a :some/int ?x]
@@ -1106,6 +1150,6 @@ mod testing {
             [:find ?x
              :where [?a :foo/age ?x]
                     [_ :foo/height ?x]]"#;
-        compare_ccs(alg(&schema, query), alg(&schema, simple));
+        compare_ccs(alg(known, query), alg(known, simple));
     }
 }

query-algebrizer/src/clauses/pattern.rs

@@ -9,10 +9,11 @@
 // specific language governing permissions and limitations under the License.
 
 use mentat_core::{
+    Entid,
     HasSchema,
-    Schema,
     TypedValue,
     ValueType,
+    ValueTypeSet,
 };
 
 use mentat_query::{
@@ -20,19 +21,28 @@ use mentat_query::{
     PatternValuePlace,
     PatternNonValuePlace,
     SrcVar,
+    Variable,
 };
 
 use super::RcCloned;
 
-use clauses::ConjoiningClauses;
+use clauses::{
+    ConjoiningClauses,
+};
 
 use types::{
     ColumnConstraint,
     DatomsColumn,
     EmptyBecause,
+    EvolvedNonValuePlace,
+    EvolvedPattern,
+    EvolvedValuePlace,
+    PlaceOrEmpty,
     SourceAlias,
 };
 
+use Known;
+
 /// Application of patterns.
 impl ConjoiningClauses {
 
@@ -71,7 +81,7 @@ impl ConjoiningClauses {
     ///   existence subquery instead of a join.
     ///
     /// This method is only public for use from `or.rs`.
-    pub fn apply_pattern_clause_for_alias<'s>(&mut self, schema: &'s Schema, pattern: &Pattern, alias: &SourceAlias) {
+    pub fn apply_pattern_clause_for_alias(&mut self, known: Known, pattern: &EvolvedPattern, alias: &SourceAlias) {
         if self.is_known_empty() {
             return;
         }
@@ -88,33 +98,25 @@ impl ConjoiningClauses {
 
         let ref col = alias.1;
 
+        let schema = known.schema;
         match pattern.entity {
-            PatternNonValuePlace::Placeholder =>
+            EvolvedNonValuePlace::Placeholder =>
                 // Placeholders don't contribute any column bindings, nor do
                 // they constrain the query -- there's no need to produce
                 // IS NOT NULL, because we don't store nulls in our schema.
                 (),
-            PatternNonValuePlace::Variable(ref v) =>
+            EvolvedNonValuePlace::Variable(ref v) =>
                 self.bind_column_to_var(schema, col.clone(), DatomsColumn::Entity, v.clone()),
-            PatternNonValuePlace::Entid(entid) =>
+            EvolvedNonValuePlace::Entid(entid) =>
                 self.constrain_column_to_entity(col.clone(), DatomsColumn::Entity, entid),
-            PatternNonValuePlace::Ident(ref ident) => {
-                if let Some(entid) = self.entid_for_ident(schema, ident.as_ref()) {
-                    self.constrain_column_to_entity(col.clone(), DatomsColumn::Entity, entid.into())
-                } else {
-                    // A resolution failure means we're done here.
-                    self.mark_known_empty(EmptyBecause::UnresolvedIdent(ident.cloned()));
-                    return;
-                }
-            }
         }
 
         match pattern.attribute {
-            PatternNonValuePlace::Placeholder =>
+            EvolvedNonValuePlace::Placeholder =>
                 (),
-            PatternNonValuePlace::Variable(ref v) =>
+            EvolvedNonValuePlace::Variable(ref v) =>
                 self.bind_column_to_var(schema, col.clone(), DatomsColumn::Attribute, v.clone()),
-            PatternNonValuePlace::Entid(entid) => {
+            EvolvedNonValuePlace::Entid(entid) => {
                 if !schema.is_attribute(entid) {
                     // Furthermore, that entid must resolve to an attribute. If it doesn't, this
                     // query is meaningless.
@@ -123,20 +125,6 @@ impl ConjoiningClauses {
                 }
                 self.constrain_attribute(col.clone(), entid)
             },
-            PatternNonValuePlace::Ident(ref ident) => {
-                if let Some(entid) = self.entid_for_ident(schema, ident) {
-                    self.constrain_attribute(col.clone(), entid.into());
-
-                    if !schema.is_attribute(entid) {
-                        self.mark_known_empty(EmptyBecause::InvalidAttributeIdent(ident.cloned()));
-                        return;
-                    }
-                } else {
-                    // A resolution failure means we're done here.
-                    self.mark_known_empty(EmptyBecause::UnresolvedIdent(ident.cloned()));
-                    return;
-                }
-            }
         }
 
         // Determine if the pattern's value type is known.
@@ -147,10 +135,10 @@ impl ConjoiningClauses {
         let value_type = self.get_value_type(schema, pattern);
 
         match pattern.value {
-            PatternValuePlace::Placeholder =>
+            EvolvedValuePlace::Placeholder =>
                 (),
 
-            PatternValuePlace::Variable(ref v) => {
+            EvolvedValuePlace::Variable(ref v) => {
                 if let Some(this_type) = value_type {
                     // Wouldn't it be nice if we didn't need to clone in the found case?
                     // It doesn't matter too much: collisons won't be too frequent.
@@ -162,7 +150,18 @@ impl ConjoiningClauses {
 
                 self.bind_column_to_var(schema, col.clone(), DatomsColumn::Value, v.clone());
             },
-            PatternValuePlace::EntidOrInteger(i) =>
+            EvolvedValuePlace::Entid(i) => {
+                match value_type {
+                    Some(ValueType::Ref) | None => {
+                        self.constrain_column_to_entity(col.clone(), DatomsColumn::Value, i);
+                    },
+                    Some(value_type) => {
+                        self.mark_known_empty(EmptyBecause::ValueTypeMismatch(value_type, TypedValue::Ref(i)));
+                    },
+                }
+            },
+
+            EvolvedValuePlace::EntidOrInteger(i) =>
                 // If we know the valueType, then we can determine whether this is an entid or an
                 // integer. If we don't, then we must generate a more general query with a
                 // value_type_tag.
@@ -180,9 +179,11 @@ impl ConjoiningClauses {
                     // - Constraining the value column to the plain numeric value '1'.
                     // - Constraining its type column to one of a set of types.
                     //
+                    // TODO: isn't there a bug here? We'll happily take a numeric value
+                    // for a non-numeric attribute!
                     self.constrain_value_to_numeric(col.clone(), i);
                 },
-            PatternValuePlace::IdentOrKeyword(ref kw) => {
+            EvolvedValuePlace::IdentOrKeyword(ref kw) => {
                 // If we know the valueType, then we can determine whether this is an ident or a
                 // keyword. If we don't, then we must generate a more general query with a
                 // value_type_tag.
@@ -204,9 +205,9 @@ impl ConjoiningClauses {
                     self.wheres.add_intersection(ColumnConstraint::has_unit_type(col.clone(), ValueType::Keyword));
                 };
             },
-            PatternValuePlace::Constant(ref c) => {
+            EvolvedValuePlace::Value(ref c) => {
                 // TODO: don't allocate.
-                let typed_value = c.clone().into_typed_value();
+                let typed_value = c.clone();
                 if !typed_value.is_congruent_with(value_type) {
                     // If the attribute and its value don't match, the pattern must fail.
                     // We can never have a congruence failure if `value_type` is `None`, so we
@@ -244,34 +245,388 @@ impl ConjoiningClauses {
         }
 
         match pattern.tx {
-            PatternNonValuePlace::Placeholder => (),
+            EvolvedNonValuePlace::Placeholder => (),
-            PatternNonValuePlace::Variable(ref v) => {
+            EvolvedNonValuePlace::Variable(ref v) => {
                 self.bind_column_to_var(schema, col.clone(), DatomsColumn::Tx, v.clone());
             },
-            PatternNonValuePlace::Entid(entid) => {
+            EvolvedNonValuePlace::Entid(entid) => {
                 self.constrain_column_to_entity(col.clone(), DatomsColumn::Tx, entid);
             },
-            PatternNonValuePlace::Ident(ref ident) => {
+        }
-                if let Some(entid) = self.entid_for_ident(schema, ident.as_ref()) {
+    }
-                    self.constrain_column_to_entity(col.clone(), DatomsColumn::Tx, entid.into())
+
+    fn reverse_lookup(&mut self, known: Known, var: &Variable, attr: Entid, val: &TypedValue) -> bool {
+        if let Some(attribute) = known.schema.attribute_for_entid(attr) {
+            let unique = attribute.unique.is_some();
+            if unique {
+                match known.get_entid_for_value(attr, val) {
+                    None => {
+                        self.mark_known_empty(EmptyBecause::CachedAttributeHasNoEntity {
+                            value: val.clone(),
+                            attr: attr,
+                        });
+                        true
+                    },
+                    Some(item) => {
+                        self.bind_value(var, TypedValue::Ref(item));
+                        true
+                    },
+                }
             } else {
-                    // A resolution failure means we're done here.
+                match known.get_entids_for_value(attr, val) {
-                    self.mark_known_empty(EmptyBecause::UnresolvedIdent(ident.cloned()));
+                    None => {
+                        self.mark_known_empty(EmptyBecause::CachedAttributeHasNoEntity {
+                            value: val.clone(),
+                            attr: attr,
+                        });
+                        true
+                    },
+                    Some(items) => {
+                        if items.len() == 1 {
+                            let item = items.iter().next().cloned().unwrap();
+                            self.bind_value(var, TypedValue::Ref(item));
+                            true
+                        } else {
+                            // Oh well.
+                            // TODO: handle multiple values.
+                            false
+                        }
+                    },
+                }
+            }
+        } else {
+            self.mark_known_empty(EmptyBecause::InvalidAttributeEntid(attr));
+            true
+        }
+    }
+
+    // TODO: generalize.
+    // TODO: use constant values -- extract transformation code from apply_pattern_clause_for_alias.
+    // TODO: loop over all patterns until no more cache values apply?
+    fn attempt_cache_lookup(&mut self, known: Known, pattern: &EvolvedPattern) -> bool {
+        // Precondition: default source. If it's not default, don't call this.
+        assert!(pattern.source == SrcVar::DefaultSrc);
+
+        let schema = known.schema;
+
+        if pattern.tx != EvolvedNonValuePlace::Placeholder {
+            return false;
+        }
+
+        // See if we can use the cache.
+        match pattern.attribute {
+            EvolvedNonValuePlace::Entid(attr) => {
+                if !schema.is_attribute(attr) {
+                    // Furthermore, that entid must resolve to an attribute. If it doesn't, this
+                    // query is meaningless.
+                    self.mark_known_empty(EmptyBecause::InvalidAttributeEntid(attr));
+                    return true;
+                }
+
+                let cached_forward = known.is_attribute_cached_forward(attr);
+                let cached_reverse = known.is_attribute_cached_reverse(attr);
+
+                if (cached_forward || cached_reverse) &&
+                   pattern.tx == EvolvedNonValuePlace::Placeholder {
+
+                    let attribute = schema.attribute_for_entid(attr).unwrap();
+
+                    // There are two patterns we can handle:
+                    //     [?e :some/unique 123 _ _]     -- reverse lookup
+                    //     [123 :some/attr ?v _ _]       -- forward lookup
+                    match pattern.entity {
+                        // Reverse lookup.
+                        EvolvedNonValuePlace::Variable(ref var) => {
+                            match pattern.value {
+                                // TODO: EntidOrInteger etc.
+                                EvolvedValuePlace::IdentOrKeyword(ref kw) => {
+                                    match attribute.value_type {
+                                        ValueType::Ref => {
+                                            // It's an ident.
+                                            // TODO
+                                            return false;
+                                        },
+                                        ValueType::Keyword => {
+                                            let tv: TypedValue = TypedValue::Keyword(kw.clone());
+                                            return self.reverse_lookup(known, var, attr, &tv);
+                                        },
+                                        t => {
+                                            let tv: TypedValue = TypedValue::Keyword(kw.clone());
+                                            // Anything else can't match an IdentOrKeyword.
+                                            self.mark_known_empty(EmptyBecause::ValueTypeMismatch(t, tv));
+                                            return true;
+                                        },
+                                    }
+                                },
+                                EvolvedValuePlace::Value(ref val) => {
+                                    if cached_reverse {
+                                        return self.reverse_lookup(known, var, attr, val);
+                                    }
+                                }
+                                _ => {},      // TODO: check constant values against cache.
+                            }
+                        },
+
+                        // Forward lookup.
+                        EvolvedNonValuePlace::Entid(entity) => {
+                            match pattern.value {
+                                EvolvedValuePlace::Variable(ref var) => {
+                                    if cached_forward {
+                                        match known.get_value_for_entid(known.schema, attr, entity) {
+                                            None => {
+                                                self.mark_known_empty(EmptyBecause::CachedAttributeHasNoValues {
+                                                    entity: entity,
+                                                    attr: attr,
+                                                });
+                                                return true;
+                                            },
+                                            Some(item) => {
+                                                println!("{} is known to be {:?}", var, item);
+                                                self.bind_value(var, item.clone());
+                                                return true;
+                                            }
+                                        }
+                                    }
+                                }
+                                _ => {},      // TODO: check constant values against cache.
+                            }
+                        },
+                        _ => {},
+                    }
+                }
+            },
+            _ => {},
+        }
+        false
+    }
+
+    /// Transform a pattern place into a narrower type.
+    /// If that's impossible, returns Empty.
+    fn make_evolved_non_value(&self, known: &Known, col: DatomsColumn, non_value: PatternNonValuePlace) -> PlaceOrEmpty<EvolvedNonValuePlace> {
+        use self::PlaceOrEmpty::*;
+        match non_value {
+            PatternNonValuePlace::Placeholder => Place(EvolvedNonValuePlace::Placeholder),
+            PatternNonValuePlace::Entid(e) => Place(EvolvedNonValuePlace::Entid(e)),
+            PatternNonValuePlace::Ident(kw) => {
+                // Resolve the ident.
+                if let Some(entid) = known.schema.get_entid(&kw) {
+                    Place(EvolvedNonValuePlace::Entid(entid.into()))
+                } else {
+                    Empty(EmptyBecause::UnresolvedIdent((&*kw).clone()))
+                }
+            },
+            PatternNonValuePlace::Variable(var) => {
+                // See if we have it!
+                match self.bound_value(&var) {
+                    None => Place(EvolvedNonValuePlace::Variable(var)),
+                    Some(TypedValue::Ref(entid)) => Place(EvolvedNonValuePlace::Entid(entid)),
+                    Some(TypedValue::Keyword(kw)) => {
+                        // We'll allow this only if it's an ident.
+                        if let Some(entid) = known.schema.get_entid(&kw) {
+                            Place(EvolvedNonValuePlace::Entid(entid.into()))
+                        } else {
+                            Empty(EmptyBecause::UnresolvedIdent((&*kw).clone()))
+                        }
+                    },
+                    Some(v) => {
+                        Empty(EmptyBecause::InvalidBinding(col.into(), v))
+                    },
+                }
+            },
+        }
+    }
+
+    fn make_evolved_entity(&self, known: &Known, entity: PatternNonValuePlace) -> PlaceOrEmpty<EvolvedNonValuePlace> {
+        self.make_evolved_non_value(known, DatomsColumn::Entity, entity)
+    }
+
+    fn make_evolved_tx(&self, known: &Known, tx: PatternNonValuePlace) -> PlaceOrEmpty<EvolvedNonValuePlace> {
+        // TODO: make sure that, if it's an entid, it names a tx.
+        self.make_evolved_non_value(known, DatomsColumn::Tx, tx)
+    }
+
+    pub fn make_evolved_attribute(&self, known: &Known, attribute: PatternNonValuePlace) -> PlaceOrEmpty<(EvolvedNonValuePlace, Option<ValueType>)> {
+        use self::PlaceOrEmpty::*;
+        self.make_evolved_non_value(known, DatomsColumn::Attribute, attribute)
+            .and_then(|a| {
+                // Make sure that, if it's an entid, it names an attribute.
+                if let EvolvedNonValuePlace::Entid(e) = a {
+                    if let Some(attr) = known.schema.attribute_for_entid(e) {
+                        Place((a, Some(attr.value_type)))
+                    } else {
+                        Empty(EmptyBecause::InvalidAttributeEntid(e))
+                    }
+                } else {
+                    Place((a, None))
+                }
+            })
+    }
+
+    pub fn make_evolved_value(&self,
+                              known: &Known,
+                              value_type: Option<ValueType>,
+                              value: PatternValuePlace) -> PlaceOrEmpty<EvolvedValuePlace> {
+        use self::PlaceOrEmpty::*;
+        match value {
+            PatternValuePlace::Placeholder => Place(EvolvedValuePlace::Placeholder),
+            PatternValuePlace::EntidOrInteger(e) => {
+                match value_type {
+                    Some(ValueType::Ref) => Place(EvolvedValuePlace::Entid(e)),
+                    Some(ValueType::Long) => Place(EvolvedValuePlace::Value(TypedValue::Long(e))),
+                    Some(ValueType::Double) => Place(EvolvedValuePlace::Value((e as f64).into())),
+                    Some(t) => Empty(EmptyBecause::ValueTypeMismatch(t, TypedValue::Long(e))),
+                    None => Place(EvolvedValuePlace::EntidOrInteger(e)),
+                }
+            },
+            PatternValuePlace::IdentOrKeyword(kw) => {
+                match value_type {
+                    Some(ValueType::Ref) => {
+                        // Resolve the ident.
+                        if let Some(entid) = known.schema.get_entid(&kw) {
+                            Place(EvolvedValuePlace::Entid(entid.into()))
+                        } else {
+                            Empty(EmptyBecause::UnresolvedIdent((&*kw).clone()))
+                        }
+                    },
+                    Some(ValueType::Keyword) => {
+                        Place(EvolvedValuePlace::Value(TypedValue::Keyword(kw)))
+                    },
+                    Some(t) => {
+                        Empty(EmptyBecause::ValueTypeMismatch(t, TypedValue::Keyword(kw)))
+                    },
+                    None => {
+                        Place(EvolvedValuePlace::IdentOrKeyword(kw))
+                    },
+                }
+            },
+            PatternValuePlace::Variable(var) => {
+                // See if we have it!
+                match self.bound_value(&var) {
+                    None => Place(EvolvedValuePlace::Variable(var)),
+                    Some(TypedValue::Ref(entid)) => {
+                        if let Some(empty) = self.can_constrain_var_to_type(&var, ValueType::Ref) {
+                            Empty(empty)
+                        } else {
+                            Place(EvolvedValuePlace::Entid(entid))
+                        }
+                    },
+                    Some(val) => {
+                        if let Some(empty) = self.can_constrain_var_to_type(&var, val.value_type()) {
+                            Empty(empty)
+                        } else {
+                            Place(EvolvedValuePlace::Value(val))
+                        }
+                    },
+                }
+            },
+            PatternValuePlace::Constant(nic) => {
+                Place(EvolvedValuePlace::Value(nic.into_typed_value()))
+            },
+        }
+    }
+
+    pub fn make_evolved_pattern(&self, known: Known, pattern: Pattern) -> PlaceOrEmpty<EvolvedPattern> {
+        let (e, a, v, tx, source) = (pattern.entity, pattern.attribute, pattern.value, pattern.tx, pattern.source);
+        use self::PlaceOrEmpty::*;
+        match self.make_evolved_entity(&known, e) {
+            Empty(because) => Empty(because),
+            Place(e) => {
+                match self.make_evolved_attribute(&known, a) {
+                    Empty(because) => Empty(because),
+                    Place((a, value_type)) => {
+                        match self.make_evolved_value(&known, value_type, v) {
+                            Empty(because) => Empty(because),
+                            Place(v) => {
+                                match self.make_evolved_tx(&known, tx) {
+                                    Empty(because) => Empty(because),
+                                    Place(tx) => {
+                                        PlaceOrEmpty::Place(EvolvedPattern {
+                                            source: source.unwrap_or(SrcVar::DefaultSrc),
+                                            entity: e,
+                                            attribute: a,
+                                            value: v,
+                                            tx: tx,
+                                        })
+                                    },
+                                }
+                            },
+                        }
+                    },
+                }
+            },
+        }
+    }
+
+    /// Re-examine the pattern to see if it can be specialized or is now known to fail.
+    #[allow(unused_variables)]
+    pub fn evolve_pattern(&mut self, known: Known, mut pattern: EvolvedPattern) -> PlaceOrEmpty<EvolvedPattern> {
+        use self::PlaceOrEmpty::*;
+
+        let mut new_entity: Option<EvolvedNonValuePlace> = None;
+        let mut new_value: Option<EvolvedValuePlace> = None;
+
+        match &pattern.entity {
+            &EvolvedNonValuePlace::Variable(ref var) => {
+                // See if we have it yet!
+                match self.bound_value(&var) {
+                    None => (),
+                    Some(TypedValue::Ref(entid)) => {
+                        new_entity = Some(EvolvedNonValuePlace::Entid(entid));
+                    },
+                    Some(v) => {
+                        return Empty(EmptyBecause::TypeMismatch {
+                            var: var.clone(),
+                            existing: self.known_type_set(&var),
+                            desired: ValueTypeSet::of_one(ValueType::Ref),
+                        });
+                    },
+                };
+            },
+            _ => (),
+        }
+        match &pattern.value {
+            &EvolvedValuePlace::Variable(ref var) => {
+                // See if we have it yet!
+                match self.bound_value(&var) {
+                    None => (),
+                    Some(tv) => {
+                        new_value = Some(EvolvedValuePlace::Value(tv.clone()));
+                    },
+                };
+            },
+            _ => (),
+        }
+
+
+        if let Some(e) = new_entity {
+            pattern.entity = e;
+        }
+        if let Some(v) = new_value {
+            pattern.value = v;
+        }
+        Place(pattern)
+    }
+
+    pub fn apply_parsed_pattern(&mut self, known: Known, pattern: Pattern) {
+        use self::PlaceOrEmpty::*;
+        match self.make_evolved_pattern(known, pattern) {
+            Empty(e) => self.mark_known_empty(e),
+            Place(p) => self.apply_pattern(known, p),
+        };
+    }
+
+    pub fn apply_pattern(&mut self, known: Known, pattern: EvolvedPattern) {
+        // For now we only support the default source.
+        if pattern.source != SrcVar::DefaultSrc {
+            unimplemented!();
+        }
+
+        if self.attempt_cache_lookup(known, &pattern) {
             return;
         }
-            }
-        }
-    }
 
-    pub fn apply_pattern<'s, 'p>(&mut self, schema: &'s Schema, pattern: Pattern) {
+        if let Some(alias) = self.alias_table(known.schema, &pattern) {
-        // For now we only support the default source.
+            self.apply_pattern_clause_for_alias(known, &pattern, &alias);
-        match pattern.source {
-            Some(SrcVar::DefaultSrc) | None => (),
-            _ => unimplemented!(),
-        };
-
-        if let Some(alias) = self.alias_table(schema, &pattern) {
-            self.apply_pattern_clause_for_alias(schema, &pattern, &alias);
             self.from.push(alias);
         } else {
             // We didn't determine a table, likely because there was a mismatch
@@ -296,6 +651,7 @@ mod testing {
     use mentat_core::attribute::Unique;
     use mentat_core::{
         Attribute,
+        Schema,
         ValueTypeSet,
     };
 
@@ -329,15 +685,17 @@ mod testing {
 
     fn alg(schema: &Schema, input: &str) -> ConjoiningClauses {
         let parsed = parse_find_string(input).expect("parse failed");
-        algebrize(schema.into(), parsed).expect("algebrize failed").cc
+        let known = Known::for_schema(schema);
+        algebrize(known, parsed).expect("algebrize failed").cc
     }
 
     #[test]
     fn test_unknown_ident() {
         let mut cc = ConjoiningClauses::default();
         let schema = Schema::default();
+        let known = Known::for_schema(&schema);
 
-        cc.apply_pattern(&schema, Pattern {
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(Variable::from_valid_name("?x")),
             attribute: ident("foo", "bar"),
@@ -355,7 +713,8 @@ mod testing {
 
         associate_ident(&mut schema, NamespacedKeyword::new("foo", "bar"), 99);
 
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(Variable::from_valid_name("?x")),
             attribute: ident("foo", "bar"),
@@ -378,7 +737,8 @@ mod testing {
         });
 
         let x = Variable::from_valid_name("?x");
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: ident("foo", "bar"),
@@ -418,7 +778,8 @@ mod testing {
         let schema = Schema::default();
 
         let x = Variable::from_valid_name("?x");
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: PatternNonValuePlace::Placeholder,
@@ -467,7 +828,8 @@ mod testing {
 
         cc.input_variables.insert(a.clone());
         cc.value_bindings.insert(a.clone(), TypedValue::Keyword(Rc::new(NamespacedKeyword::new("foo", "bar"))));
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: PatternNonValuePlace::Variable(a.clone()),
@@ -510,7 +872,8 @@ mod testing {
 
         cc.input_variables.insert(a.clone());
         cc.value_bindings.insert(a.clone(), hello.clone());
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: PatternNonValuePlace::Variable(a.clone()),
@@ -532,7 +895,8 @@ mod testing {
         let x = Variable::from_valid_name("?x");
         let a = Variable::from_valid_name("?a");
         let v = Variable::from_valid_name("?v");
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: PatternNonValuePlace::Variable(a.clone()),
@@ -562,7 +926,8 @@ mod testing {
         let schema = Schema::default();
 
         let x = Variable::from_valid_name("?x");
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: PatternNonValuePlace::Placeholder,
@@ -612,14 +977,15 @@ mod testing {
 
         let x = Variable::from_valid_name("?x");
         let y = Variable::from_valid_name("?y");
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: ident("foo", "roz"),
             value: PatternValuePlace::Constant(NonIntegerConstant::Text(Rc::new("idgoeshere".to_string()))),
             tx: PatternNonValuePlace::Placeholder,
         });
-        cc.apply_pattern(&schema, Pattern {
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: ident("foo", "bar"),
@@ -686,7 +1052,8 @@ mod testing {
         let variables: BTreeSet<Variable> = vec![Variable::from_valid_name("?y")].into_iter().collect();
         let mut cc = ConjoiningClauses::with_inputs(variables, inputs);
 
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: ident("foo", "bar"),
@@ -733,7 +1100,8 @@ mod testing {
         let variables: BTreeSet<Variable> = vec![Variable::from_valid_name("?y")].into_iter().collect();
         let mut cc = ConjoiningClauses::with_inputs(variables, inputs);
 
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: ident("foo", "bar"),
@@ -768,7 +1136,8 @@ mod testing {
         let variables: BTreeSet<Variable> = vec![Variable::from_valid_name("?y")].into_iter().collect();
         let mut cc = ConjoiningClauses::with_inputs(variables, inputs);
 
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: ident("foo", "bar"),
@@ -802,14 +1171,15 @@ mod testing {
 
         let x = Variable::from_valid_name("?x");
         let y = Variable::from_valid_name("?y");
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: ident("foo", "roz"),
             value: PatternValuePlace::Variable(y.clone()),
             tx: PatternNonValuePlace::Placeholder,
         });
-        cc.apply_pattern(&schema, Pattern {
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: ident("foo", "bar"),
@@ -844,14 +1214,15 @@ mod testing {
         let x = Variable::from_valid_name("?x");
         let y = Variable::from_valid_name("?y");
         let z = Variable::from_valid_name("?z");
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: PatternNonValuePlace::Variable(y.clone()),
             value: PatternValuePlace::Constant(NonIntegerConstant::Boolean(true)),
             tx: PatternNonValuePlace::Placeholder,
         });
-        cc.apply_pattern(&schema, Pattern {
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(z.clone()),
             attribute: PatternNonValuePlace::Variable(y.clone()),

query-algebrizer/src/clauses/predicate.rs

@@ -35,6 +35,8 @@ use types::{
     Inequality,
 };
 
+use Known;
+
 /// Application of predicates.
 impl ConjoiningClauses {
     /// There are several kinds of predicates in our Datalog:
@@ -43,11 +45,11 @@ impl ConjoiningClauses {
     /// - In the future, some predicates that are implemented via function calls in SQLite.
     ///
     /// At present we have implemented only the five built-in comparison binary operators.
-    pub fn apply_predicate<'s>(&mut self, schema: &'s Schema, predicate: Predicate) -> Result<()> {
+    pub fn apply_predicate(&mut self, known: Known, predicate: Predicate) -> Result<()> {
         // Because we'll be growing the set of built-in predicates, handling each differently,
         // and ultimately allowing user-specified predicates, we match on the predicate name first.
         if let Some(op) = Inequality::from_datalog_operator(predicate.operator.0.as_str()) {
-            self.apply_inequality(schema, op, predicate)
+            self.apply_inequality(known, op, predicate)
         } else {
             bail!(ErrorKind::UnknownFunction(predicate.operator.clone()))
         }
@@ -71,7 +73,7 @@ impl ConjoiningClauses {
     /// - Resolves variables and converts types to those more amenable to SQL.
     /// - Ensures that the predicate functions name a known operator.
     /// - Accumulates an `Inequality` constraint into the `wheres` list.
-    pub fn apply_inequality<'s>(&mut self, schema: &'s Schema, comparison: Inequality, predicate: Predicate) -> Result<()> {
+    pub fn apply_inequality(&mut self, known: Known, comparison: Inequality, predicate: Predicate) -> Result<()> {
         if predicate.args.len() != 2 {
             bail!(ErrorKind::InvalidNumberOfArguments(predicate.operator.clone(), predicate.args.len(), 2));
         }
@@ -87,13 +89,13 @@ impl ConjoiningClauses {
         // The types we're handling here must be the intersection of the possible types of the arguments,
         // the known types of any variables, and the types supported by our inequality operators.
         let supported_types = comparison.supported_types();
-        let mut left_types = self.potential_types(schema, &left)?
+        let mut left_types = self.potential_types(known.schema, &left)?
                                  .intersection(&supported_types);
         if left_types.is_empty() {
             bail!(ErrorKind::InvalidArgument(predicate.operator.clone(), "numeric or instant", 0));
         }
 
-        let mut right_types = self.potential_types(schema, &right)?
+        let mut right_types = self.potential_types(known.schema, &right)?
                                   .intersection(&supported_types);
         if right_types.is_empty() {
             bail!(ErrorKind::InvalidArgument(predicate.operator.clone(), "numeric or instant", 1));
@@ -203,7 +205,8 @@ mod testing {
 
         let x = Variable::from_valid_name("?x");
         let y = Variable::from_valid_name("?y");
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: PatternNonValuePlace::Placeholder,
@@ -214,7 +217,7 @@ mod testing {
 
         let op = PlainSymbol::new("<");
         let comp = Inequality::from_datalog_operator(op.plain_name()).unwrap();
-        assert!(cc.apply_inequality(&schema, comp, Predicate {
+        assert!(cc.apply_inequality(known, comp, Predicate {
              operator: op,
              args: vec![
                 FnArg::Variable(Variable::from_valid_name("?y")), FnArg::EntidOrInteger(10),
@@ -263,7 +266,8 @@ mod testing {
 
         let x = Variable::from_valid_name("?x");
         let y = Variable::from_valid_name("?y");
-        cc.apply_pattern(&schema, Pattern {
+        let known = Known::for_schema(&schema);
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: PatternNonValuePlace::Placeholder,
@@ -274,14 +278,14 @@ mod testing {
 
         let op = PlainSymbol::new(">=");
         let comp = Inequality::from_datalog_operator(op.plain_name()).unwrap();
-        assert!(cc.apply_inequality(&schema, comp, Predicate {
+        assert!(cc.apply_inequality(known, comp, Predicate {
              operator: op,
              args: vec![
                 FnArg::Variable(Variable::from_valid_name("?y")), FnArg::EntidOrInteger(10),
             ]}).is_ok());
 
         assert!(!cc.is_known_empty());
-        cc.apply_pattern(&schema, Pattern {
+        cc.apply_parsed_pattern(known, Pattern {
             source: None,
             entity: PatternNonValuePlace::Variable(x.clone()),
             attribute: ident("foo", "roz"),

query-algebrizer/src/clauses/where_fn.rs

@@ -8,10 +8,6 @@
 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
 // specific language governing permissions and limitations under the License.
 
-use mentat_core::{
-    Schema,
-};
-
 use mentat_query::{
     WhereFn,
 };
@@ -25,6 +21,8 @@ use errors::{
     Result,
 };
 
+use Known;
+
 /// Application of `where` functions.
 impl ConjoiningClauses {
     /// There are several kinds of functions binding variables in our Datalog:
@@ -33,12 +31,12 @@ impl ConjoiningClauses {
     /// - In the future, some functions that are implemented via function calls in SQLite.
     ///
     /// At present we have implemented only a limited selection of functions.
-    pub fn apply_where_fn<'s>(&mut self, schema: &'s Schema, where_fn: WhereFn) -> Result<()> {
+    pub fn apply_where_fn(&mut self, known: Known, where_fn: WhereFn) -> Result<()> {
         // Because we'll be growing the set of built-in functions, handling each differently, and
         // ultimately allowing user-specified functions, we match on the function name first.
         match where_fn.operator.0.as_str() {
-            "fulltext" => self.apply_fulltext(schema, where_fn),
+            "fulltext" => self.apply_fulltext(known, where_fn),
-            "ground" => self.apply_ground(schema, where_fn),
+            "ground" => self.apply_ground(known, where_fn),
             _ => bail!(ErrorKind::UnknownFunction(where_fn.operator.clone())),
         }
     }

query-algebrizer/src/lib.rs

@@ -28,6 +28,8 @@ mod validate;
 mod clauses;
 
 use mentat_core::{
+    CachedAttributes,
+    Entid,
     Schema,
     TypedValue,
     ValueType,
@@ -59,6 +61,68 @@ pub use types::{
     EmptyBecause,
 };
 
+/// A convenience wrapper around things known in memory: the schema and caches.
+/// We use a trait object here to avoid making dozens of functions generic over the type
+/// of the cache. If performance becomes a concern, we should hard-code specific kinds of
+/// cache right here, and/or eliminate the Option.
+#[derive(Clone, Copy)]
+pub struct Known<'s, 'c> {
+    pub schema: &'s Schema,
+    pub cache: Option<&'c CachedAttributes>,
+}
+
+impl<'s, 'c> Known<'s, 'c> {
+    pub fn for_schema(s: &'s Schema) -> Known<'s, 'static> {
+        Known {
+            schema: s,
+            cache: None,
+        }
+    }
+
+    pub fn new(s: &'s Schema, c: Option<&'c CachedAttributes>) -> Known<'s, 'c> {
+        Known {
+            schema: s,
+            cache: c,
+        }
+    }
+}
+
+/// This is `CachedAttributes`, but with handy generic parameters.
+/// Why not make the trait generic? Because then we can't use it as a trait object in `Known`.
+impl<'s, 'c> Known<'s, 'c> {
+    pub fn is_attribute_cached_reverse<U>(&self, entid: U) -> bool where U: Into<Entid> {
+        self.cache
+            .map(|cache| cache.is_attribute_cached_reverse(entid.into()))
+            .unwrap_or(false)
+    }
+
+    pub fn is_attribute_cached_forward<U>(&self, entid: U) -> bool where U: Into<Entid> {
+        self.cache
+            .map(|cache| cache.is_attribute_cached_forward(entid.into()))
+            .unwrap_or(false)
+    }
+
+    pub fn get_values_for_entid<U, V>(&self, schema: &Schema, attribute: U, entid: V) -> Option<&Vec<TypedValue>>
+    where U: Into<Entid>, V: Into<Entid> {
+        self.cache.and_then(|cache| cache.get_values_for_entid(schema, attribute.into(), entid.into()))
+    }
+
+    pub fn get_value_for_entid<U, V>(&self, schema: &Schema, attribute: U, entid: V) -> Option<&TypedValue>
+    where U: Into<Entid>, V: Into<Entid> {
+        self.cache.and_then(|cache| cache.get_value_for_entid(schema, attribute.into(), entid.into()))
+    }
+
+    pub fn get_entid_for_value<U>(&self, attribute: U, value: &TypedValue) -> Option<Entid>
+    where U: Into<Entid> {
+        self.cache.and_then(|cache| cache.get_entid_for_value(attribute.into(), value))
+    }
+
+    pub fn get_entids_for_value<U>(&self, attribute: U, value: &TypedValue) -> Option<&BTreeSet<Entid>>
+    where U: Into<Entid> {
+        self.cache.and_then(|cache| cache.get_entids_for_value(attribute.into(), value))
+    }
+}
+
 #[derive(Debug)]
 pub struct AlgebraicQuery {
     default_source: SrcVar,
@@ -83,12 +147,12 @@ impl AlgebraicQuery {
     }
 }
 
-pub fn algebrize_with_counter(schema: &Schema, parsed: FindQuery, counter: usize) -> Result<AlgebraicQuery> {
+pub fn algebrize_with_counter(known: Known, parsed: FindQuery, counter: usize) -> Result<AlgebraicQuery> {
-    algebrize_with_inputs(schema, parsed, counter, QueryInputs::default())
+    algebrize_with_inputs(known, parsed, counter, QueryInputs::default())
 }
 
-pub fn algebrize(schema: &Schema, parsed: FindQuery) -> Result<AlgebraicQuery> {
+pub fn algebrize(known: Known, parsed: FindQuery) -> Result<AlgebraicQuery> {
-    algebrize_with_inputs(schema, parsed, 0, QueryInputs::default())
+    algebrize_with_inputs(known, parsed, 0, QueryInputs::default())
 }
 
 /// Take an ordering list. Any variables that aren't fixed by the query are used to produce
@@ -166,7 +230,7 @@ fn simplify_limit(mut query: AlgebraicQuery) -> Result<AlgebraicQuery> {
     Ok(query)
 }
 
-pub fn algebrize_with_inputs(schema: &Schema,
+pub fn algebrize_with_inputs(known: Known,
                              parsed: FindQuery,
                              counter: usize,
                              inputs: QueryInputs) -> Result<AlgebraicQuery> {
@@ -180,7 +244,7 @@ pub fn algebrize_with_inputs(schema: &Schema,
 
     // TODO: integrate default source into pattern processing.
     // TODO: flesh out the rest of find-into-context.
-    cc.apply_clauses(schema, parsed.where_clauses)?;
+    cc.apply_clauses(known, parsed.where_clauses)?;
 
     cc.expand_column_bindings();
     cc.prune_extracted_types();

query-algebrizer/src/types.rs

@@ -15,6 +15,8 @@ use std::fmt::{
     Result,
 };
 
+use std::rc::Rc;
+
 use mentat_core::{
     Entid,
     TypedValue,
@@ -26,6 +28,7 @@ use mentat_query::{
     Direction,
     NamespacedKeyword,
     Order,
+    SrcVar,
     Variable,
 };
 
@@ -489,6 +492,8 @@ impl Debug for ColumnConstraint {
 
 #[derive(PartialEq, Clone)]
 pub enum EmptyBecause {
+    CachedAttributeHasNoValues { entity: Entid, attr: Entid },
+    CachedAttributeHasNoEntity { value: TypedValue, attr: Entid },
     ConflictingBindings { var: Variable, existing: TypedValue, desired: TypedValue },
 
     // A variable is known to be of two conflicting sets of types.
@@ -501,6 +506,7 @@ pub enum EmptyBecause {
     NonInstantArgument,
     NonNumericArgument,
     NonStringFulltextValue,
+    NonFulltextAttribute(Entid),
     UnresolvedIdent(NamespacedKeyword),
     InvalidAttributeIdent(NamespacedKeyword),
     InvalidAttributeEntid(Entid),
@@ -513,6 +519,12 @@ impl Debug for EmptyBecause {
     fn fmt(&self, f: &mut Formatter) -> ::std::fmt::Result {
         use self::EmptyBecause::*;
         match self {
+            &CachedAttributeHasNoEntity { ref value, ref attr } => {
+                write!(f, "(?e, {}, {:?}, _) not present in store", attr, value)
+            },
+            &CachedAttributeHasNoValues { ref entity, ref attr } => {
+                write!(f, "({}, {}, ?v, _) not present in store", entity, attr)
+            },
             &ConflictingBindings { ref var, ref existing, ref desired } => {
                 write!(f, "Var {:?} can't be {:?} because it's already bound to {:?}",
                        var, desired, existing)
@@ -549,6 +561,9 @@ impl Debug for EmptyBecause {
             &InvalidAttributeEntid(entid) => {
                 write!(f, "{} is not an attribute", entid)
             },
+            &NonFulltextAttribute(entid) => {
+                write!(f, "{} is not a fulltext attribute", entid)
+            },
             &InvalidBinding(ref column, ref tv) => {
                 write!(f, "{:?} cannot name column {:?}", tv, column)
             },
@@ -562,3 +577,52 @@ impl Debug for EmptyBecause {
         }
     }
 }
+
+// Intermediate data structures for resolving patterns.
+
+#[derive(Debug, Eq, PartialEq)]
+pub enum EvolvedNonValuePlace {
+    Placeholder,
+    Variable(Variable),
+    Entid(Entid),                       // Will always be +ve. See #190.
+}
+
+// TODO: some of these aren't necessary?
+#[derive(Debug, Eq, PartialEq)]
+pub enum EvolvedValuePlace {
+    Placeholder,
+    Variable(Variable),
+    Entid(Entid),
+    Value(TypedValue),
+    EntidOrInteger(i64),
+    IdentOrKeyword(Rc<NamespacedKeyword>),
+}
+
+pub enum PlaceOrEmpty<T> {
+    Place(T),
+    Empty(EmptyBecause),
+}
+
+impl<T> PlaceOrEmpty<T> {
+    pub fn and_then<U, F: FnOnce(T) -> PlaceOrEmpty<U>>(self, f: F) -> PlaceOrEmpty<U> {
+        match self {
+            PlaceOrEmpty::Place(x) => f(x),
+            PlaceOrEmpty::Empty(e) => PlaceOrEmpty::Empty(e),
+        }
+    }
+
+    pub fn then<F: FnOnce(T)>(self, f: F) {
+        match self {
+            PlaceOrEmpty::Place(x) => f(x),
+            PlaceOrEmpty::Empty(_e) => (),
+        }
+    }
+}
+
+pub struct EvolvedPattern {
+    pub source: SrcVar,
+    pub entity: EvolvedNonValuePlace,
+    pub attribute: EvolvedNonValuePlace,
+    pub value: EvolvedValuePlace,
+    pub tx: EvolvedNonValuePlace,
+}

query-algebrizer/tests/fulltext.rs

@@ -31,6 +31,8 @@ use utils::{
     associate_ident,
 };
 
+use mentat_query_algebrizer::Known;
+
 fn prepopulated_schema() -> Schema {
     let mut schema = Schema::default();
     associate_ident(&mut schema, NamespacedKeyword::new("foo", "name"), 65);
@@ -71,15 +73,16 @@ fn prepopulated_schema() -> Schema {
 #[test]
 fn test_apply_fulltext() {
     let schema = prepopulated_schema();
+    let known = Known::for_schema(&schema);
 
     // If you use a non-FTS attribute, we will short-circuit.
     let query = r#"[:find ?val
                     :where [(fulltext $ :foo/name "hello") [[?entity ?val _ _]]]]"#;
-    assert!(alg(&schema, query).is_known_empty());
+    assert!(alg(known, query).is_known_empty());
 
     // If you get a type mismatch, we will short-circuit.
     let query = r#"[:find ?val
                     :where [(fulltext $ :foo/description "hello") [[?entity ?val ?tx ?score]]]
                     [?score :foo/bar _]]"#;
-    assert!(alg(&schema, query).is_known_empty());
+    assert!(alg(known, query).is_known_empty());
 }

query-algebrizer/tests/ground.rs

@@ -35,6 +35,7 @@ use mentat_query_algebrizer::{
     ComputedTable,
     Error,
     ErrorKind,
+    Known,
     QueryInputs,
 };
 
@@ -87,7 +88,8 @@ fn test_ground_doesnt_bail_for_type_conflicts() {
     // The query can return no results.
     let q = r#"[:find ?x :where [?x :foo/knows ?p] [(ground 9.95) ?x]]"#;
     let schema = prepopulated_schema();
-    let cc = alg(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let cc = alg(known, &q);
     assert!(cc.empty_because.is_some());
 }
 
@@ -95,7 +97,8 @@ fn test_ground_doesnt_bail_for_type_conflicts() {
 fn test_ground_tuple_fails_impossible() {
     let q = r#"[:find ?x :where [?x :foo/knows ?p] [(ground [5 9.95]) [?x ?p]]]"#;
     let schema = prepopulated_schema();
-    let cc = alg(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let cc = alg(known, &q);
     assert!(cc.empty_because.is_some());
 }
 
@@ -103,7 +106,8 @@ fn test_ground_tuple_fails_impossible() {
 fn test_ground_scalar_fails_impossible() {
     let q = r#"[:find ?x :where [?x :foo/knows ?p] [(ground true) ?p]]"#;
     let schema = prepopulated_schema();
-    let cc = alg(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let cc = alg(known, &q);
     assert!(cc.empty_because.is_some());
 }
 
@@ -113,7 +117,8 @@ fn test_ground_coll_skips_impossible() {
     // The query can return no results.
     let q = r#"[:find ?x :where [?x :foo/knows ?p] [(ground [5 9.95 11]) [?x ...]]]"#;
     let schema = prepopulated_schema();
-    let cc = alg(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let cc = alg(known, &q);
     assert!(cc.empty_because.is_none());
     assert_eq!(cc.computed_tables[0], ComputedTable::NamedValues {
         names: vec![Variable::from_valid_name("?x")],
@@ -125,7 +130,8 @@ fn test_ground_coll_skips_impossible() {
 fn test_ground_coll_fails_if_all_impossible() {
     let q = r#"[:find ?x :where [?x :foo/knows ?p] [(ground [5.1 5.2]) [?p ...]]]"#;
     let schema = prepopulated_schema();
-    let cc = alg(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let cc = alg(known, &q);
     assert!(cc.empty_because.is_some());
 }
 
@@ -133,7 +139,8 @@ fn test_ground_coll_fails_if_all_impossible() {
 fn test_ground_rel_skips_impossible() {
     let q = r#"[:find ?x :where [?x :foo/knows ?p] [(ground [[8 "foo"] [5 7] [9.95 9] [11 12]]) [[?x ?p]]]]"#;
     let schema = prepopulated_schema();
-    let cc = alg(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let cc = alg(known, &q);
     assert!(cc.empty_because.is_none());
     assert_eq!(cc.computed_tables[0], ComputedTable::NamedValues {
         names: vec![Variable::from_valid_name("?x"), Variable::from_valid_name("?p")],
@@ -145,7 +152,8 @@ fn test_ground_rel_skips_impossible() {
 fn test_ground_rel_fails_if_all_impossible() {
     let q = r#"[:find ?x :where [?x :foo/knows ?p] [(ground [[11 5.1] [12 5.2]]) [[?x ?p]]]]"#;
     let schema = prepopulated_schema();
-    let cc = alg(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let cc = alg(known, &q);
     assert!(cc.empty_because.is_some());
 }
 
@@ -153,21 +161,24 @@ fn test_ground_rel_fails_if_all_impossible() {
 fn test_ground_tuple_rejects_all_placeholders() {
     let q = r#"[:find ?x :where [?x :foo/knows ?p] [(ground [8 "foo" 3]) [_ _ _]]]"#;
     let schema = prepopulated_schema();
-    bails(&schema, &q);
+    let known = Known::for_schema(&schema);
+    bails(known, &q);
 }
 
 #[test]
 fn test_ground_rel_rejects_all_placeholders() {
     let q = r#"[:find ?x :where [?x :foo/knows ?p] [(ground [[8 "foo"]]) [[_ _]]]]"#;
     let schema = prepopulated_schema();
-    bails(&schema, &q);
+    let known = Known::for_schema(&schema);
+    bails(known, &q);
 }
 
 #[test]
 fn test_ground_tuple_placeholders() {
     let q = r#"[:find ?x :where [?x :foo/knows ?p] [(ground [8 "foo" 3]) [?x _ ?p]]]"#;
     let schema = prepopulated_schema();
-    let cc = alg(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let cc = alg(known, &q);
     assert!(cc.empty_because.is_none());
     assert_eq!(cc.bound_value(&Variable::from_valid_name("?x")), Some(TypedValue::Ref(8)));
     assert_eq!(cc.bound_value(&Variable::from_valid_name("?p")), Some(TypedValue::Ref(3)));
@@ -177,7 +188,8 @@ fn test_ground_tuple_placeholders() {
 fn test_ground_rel_placeholders() {
     let q = r#"[:find ?x :where [?x :foo/knows ?p] [(ground [[8 "foo" 3] [5 false 7] [5 9.95 9]]) [[?x _ ?p]]]]"#;
     let schema = prepopulated_schema();
-    let cc = alg(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let cc = alg(known, &q);
     assert!(cc.empty_because.is_none());
     assert_eq!(cc.computed_tables[0], ComputedTable::NamedValues {
         names: vec![Variable::from_valid_name("?x"), Variable::from_valid_name("?p")],
@@ -197,7 +209,8 @@ fn test_ground_rel_placeholders() {
 fn test_multiple_reference_type_failure() {
     let q = r#"[:find ?x :where [?x :foo/age ?y] [?x :foo/knows ?y]]"#;
     let schema = prepopulated_schema();
-    let cc = alg(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let cc = alg(known, &q);
     assert!(cc.empty_because.is_some());
 }
 
@@ -205,7 +218,8 @@ fn test_multiple_reference_type_failure() {
 fn test_ground_tuple_infers_types() {
     let q = r#"[:find ?x :where [?x :foo/age ?v] [(ground [8 10]) [?x ?v]]]"#;
     let schema = prepopulated_schema();
-    let cc = alg(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let cc = alg(known, &q);
     assert!(cc.empty_because.is_none());
     assert_eq!(cc.bound_value(&Variable::from_valid_name("?x")), Some(TypedValue::Ref(8)));
     assert_eq!(cc.bound_value(&Variable::from_valid_name("?v")), Some(TypedValue::Long(10)));
@@ -215,7 +229,8 @@ fn test_ground_tuple_infers_types() {
 fn test_ground_rel_infers_types() {
     let q = r#"[:find ?x :where [?x :foo/age ?v] [(ground [[8 10]]) [[?x ?v]]]]"#;
     let schema = prepopulated_schema();
-    let cc = alg(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let cc = alg(known, &q);
     assert!(cc.empty_because.is_none());
     assert_eq!(cc.computed_tables[0], ComputedTable::NamedValues {
         names: vec![Variable::from_valid_name("?x"), Variable::from_valid_name("?v")],
@@ -227,7 +242,8 @@ fn test_ground_rel_infers_types() {
 fn test_ground_coll_heterogeneous_types() {
     let q = r#"[:find ?x :where [?x _ ?v] [(ground [false 8.5]) [?v ...]]]"#;
     let schema = prepopulated_schema();
-    let e = bails(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let e = bails(known, &q);
     match e {
         Error(ErrorKind::InvalidGroundConstant, _) => {
         },
@@ -241,7 +257,8 @@ fn test_ground_coll_heterogeneous_types() {
 fn test_ground_rel_heterogeneous_types() {
     let q = r#"[:find ?x :where [?x _ ?v] [(ground [[false] [5]]) [[?v]]]]"#;
     let schema = prepopulated_schema();
-    let e = bails(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let e = bails(known, &q);
     match e {
         Error(ErrorKind::InvalidGroundConstant, _) => {
         },
@@ -255,7 +272,8 @@ fn test_ground_rel_heterogeneous_types() {
 fn test_ground_tuple_duplicate_vars() {
     let q = r#"[:find ?x :where [?x :foo/age ?v] [(ground [8 10]) [?x ?x]]]"#;
     let schema = prepopulated_schema();
-    let e = bails(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let e = bails(known, &q);
     match e {
         Error(ErrorKind::InvalidBinding(v, e), _) => {
             assert_eq!(v, PlainSymbol::new("ground"));
@@ -271,7 +289,8 @@ fn test_ground_tuple_duplicate_vars() {
 fn test_ground_rel_duplicate_vars() {
     let q = r#"[:find ?x :where [?x :foo/age ?v] [(ground [[8 10]]) [[?x ?x]]]]"#;
     let schema = prepopulated_schema();
-    let e = bails(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let e = bails(known, &q);
     match e {
         Error(ErrorKind::InvalidBinding(v, e), _) => {
             assert_eq!(v, PlainSymbol::new("ground"));
@@ -287,7 +306,8 @@ fn test_ground_rel_duplicate_vars() {
 fn test_ground_nonexistent_variable_invalid() {
     let q = r#"[:find ?x ?e :where [?e _ ?x] (not [(ground 17) ?v])]"#;
     let schema = prepopulated_schema();
-    let e = bails(&schema, &q);
+    let known = Known::for_schema(&schema);
+    let e = bails(known, &q);
     match e {
         Error(ErrorKind::UnboundVariable(PlainSymbol(v)), _) => {
             assert_eq!(v, "?v".to_string());
@@ -301,6 +321,7 @@ fn test_ground_nonexistent_variable_invalid() {
 #[test]
 fn test_unbound_input_variable_invalid() {
     let schema = prepopulated_schema();
+    let known = Known::for_schema(&schema);
     let q = r#"[:find ?y ?age :in ?x :where [(ground [?x]) [?y ...]] [?y :foo/age ?age]]"#;
 
     // This fails even if we know the type: we don't support grounding bindings
@@ -310,7 +331,7 @@ fn test_unbound_input_variable_invalid() {
 
     let i = QueryInputs::new(types, BTreeMap::default()).expect("valid QueryInputs");
 
-    let e = bails_with_inputs(&schema, &q, i);
+    let e = bails_with_inputs(known, &q, i);
     match e {
         Error(ErrorKind::UnboundVariable(v), _) => {
             assert_eq!(v.0, "?x");

query-algebrizer/tests/predicate.rs

@@ -31,6 +31,7 @@ use mentat_query::{
 use mentat_query_algebrizer::{
     EmptyBecause,
     ErrorKind,
+    Known,
 };
 
 use utils::{
@@ -60,13 +61,14 @@ fn prepopulated_schema() -> Schema {
 #[test]
 fn test_instant_predicates_require_instants() {
     let schema = prepopulated_schema();
+    let known = Known::for_schema(&schema);
 
     // You can't use a string for an inequality: this is a straight-up error.
     let query = r#"[:find ?e
                     :where
                     [?e :foo/date ?t]
                     [(> ?t "2017-06-16T00:56:41.257Z")]]"#;
-    match bails(&schema, query).0 {
+    match bails(known, query).0 {
         ErrorKind::InvalidArgument(op, why, idx) => {
             assert_eq!(op, PlainSymbol::new(">"));
             assert_eq!(why, "numeric or instant");
@@ -79,7 +81,7 @@ fn test_instant_predicates_require_instants() {
                     :where
                     [?e :foo/date ?t]
                     [(> "2017-06-16T00:56:41.257Z", ?t)]]"#;
-    match bails(&schema, query).0 {
+    match bails(known, query).0 {
         ErrorKind::InvalidArgument(op, why, idx) => {
             assert_eq!(op, PlainSymbol::new(">"));
             assert_eq!(why, "numeric or instant");
@@ -95,7 +97,7 @@ fn test_instant_predicates_require_instants() {
                     :where
                     [?e :foo/date ?t]
                     [(> ?t 1234512345)]]"#;
-    let cc = alg(&schema, query);
+    let cc = alg(known, query);
     assert!(cc.is_known_empty());
     assert_eq!(cc.empty_because.unwrap(),
                EmptyBecause::TypeMismatch {
@@ -109,7 +111,7 @@ fn test_instant_predicates_require_instants() {
                     :where
                     [?e :foo/double ?t]
                     [(< ?t 1234512345)]]"#;
-    let cc = alg(&schema, query);
+    let cc = alg(known, query);
     assert!(!cc.is_known_empty());
     assert_eq!(cc.known_type(&Variable::from_valid_name("?t")).expect("?t is known"),
                ValueType::Double);

query-algebrizer/tests/type_reqs.rs

@@ -26,6 +26,8 @@ use mentat_core::{
     ValueType,
 };
 
+use mentat_query_algebrizer::Known;
+
 fn prepopulated_schema() -> Schema {
     SchemaBuilder::new()
         .define_simple_attr("test", "boolean", ValueType::Boolean, false)
@@ -52,12 +54,13 @@ fn test_empty_known() {
         "ref",
     ];
     let schema = prepopulated_schema();
+    let known = Known::for_schema(&schema);
     for known_type in type_names.iter() {
         for required in type_names.iter() {
             let q = format!("[:find ?e :where [?e :test/{} ?v] [({} ?v)]]",
                             known_type, required);
             println!("Query: {}", q);
-            let cc = alg(&schema, &q);
+            let cc = alg(known, &q);
             // It should only be empty if the known type and our requirement differ.
             assert_eq!(cc.empty_because.is_some(), known_type != required,
                        "known_type = {}; required = {}", known_type, required);
@@ -68,13 +71,15 @@ fn test_empty_known() {
 #[test]
 fn test_multiple() {
     let schema = prepopulated_schema();
+    let known = Known::for_schema(&schema);
     let q = "[:find ?e :where [?e _ ?v] [(long ?v)] [(double ?v)]]";
-    let cc = alg(&schema, &q);
+    let cc = alg(known, &q);
     assert!(cc.empty_because.is_some());
 }
 
 #[test]
 fn test_unbound() {
     let schema = prepopulated_schema();
-    bails(&schema, "[:find ?e :where [(string ?e)]]");
+    let known = Known::for_schema(&schema);
+    bails(known, "[:find ?e :where [(string ?e)]]");
 }

query-algebrizer/tests/utils/mod.rs

@@ -29,11 +29,12 @@ use mentat_query::{
 };
 
 use mentat_query_algebrizer::{
-    algebrize,
-    algebrize_with_inputs,
     ConjoiningClauses,
     Error,
+    Known,
     QueryInputs,
+    algebrize,
+    algebrize_with_inputs,
 };
 
 // Common utility functions used in multiple test files.
@@ -83,17 +84,17 @@ impl SchemaBuilder {
     }
 }
 
-pub fn bails(schema: &Schema, input: &str) -> Error {
+pub fn bails(known: Known, input: &str) -> Error {
     let parsed = parse_find_string(input).expect("query input to have parsed");
-    algebrize(schema.into(), parsed).expect_err("algebrize to have failed")
+    algebrize(known, parsed).expect_err("algebrize to have failed")
 }
 
-pub fn bails_with_inputs(schema: &Schema, input: &str, inputs: QueryInputs) -> Error {
+pub fn bails_with_inputs(known: Known, input: &str, inputs: QueryInputs) -> Error {
     let parsed = parse_find_string(input).expect("query input to have parsed");
-    algebrize_with_inputs(schema, parsed, 0, inputs).expect_err("algebrize to have failed")
+    algebrize_with_inputs(known, parsed, 0, inputs).expect_err("algebrize to have failed")
 }
 
-pub fn alg(schema: &Schema, input: &str) -> ConjoiningClauses {
+pub fn alg(known: Known, input: &str) -> ConjoiningClauses {
     let parsed = parse_find_string(input).expect("query input to have parsed");
-    algebrize(schema.into(), parsed).expect("algebrizing to have succeeded").cc
+    algebrize(known, parsed).expect("algebrizing to have succeeded").cc
 }

query-translator/tests/translate.rs

@@ -34,6 +34,7 @@ use mentat_core::{
 
 use mentat_query_parser::parse_find_string;
 use mentat_query_algebrizer::{
+    Known,
     QueryInputs,
     algebrize,
     algebrize_with_inputs,
@@ -54,8 +55,9 @@ fn add_attribute(schema: &mut Schema, e: Entid, a: Attribute) {
 }
 
 fn translate_with_inputs(schema: &Schema, query: &'static str, inputs: QueryInputs) -> SQLQuery {
+    let known = Known::for_schema(schema);
     let parsed = parse_find_string(query).expect("parse to succeed");
-    let algebrized = algebrize_with_inputs(schema, parsed, 0, inputs).expect("algebrize to succeed");
+    let algebrized = algebrize_with_inputs(known, parsed, 0, inputs).expect("algebrize to succeed");
     let select = query_to_select(algebrized).expect("translate to succeed");
     select.query.to_sql_query().unwrap()
 }
@@ -182,10 +184,11 @@ fn test_bound_variable_limit_affects_distinct() {
 #[test]
 fn test_bound_variable_limit_affects_types() {
     let schema = prepopulated_schema();
+    let known = Known::for_schema(&schema);
 
     let query = r#"[:find ?x ?limit :in ?limit :where [?x _ ?limit] :limit ?limit]"#;
     let parsed = parse_find_string(query).expect("parse failed");
-    let algebrized = algebrize(&schema, parsed).expect("algebrize failed");
+    let algebrized = algebrize(known, parsed).expect("algebrize failed");
 
     // The type is known.
     assert_eq!(Some(ValueType::Long),
@@ -272,10 +275,11 @@ fn test_unknown_attribute_integer_value() {
 #[test]
 fn test_unknown_ident() {
     let schema = Schema::default();
+    let known = Known::for_schema(&schema);
 
     let impossible = r#"[:find ?x :where [?x :db/ident :no/exist]]"#;
     let parsed = parse_find_string(impossible).expect("parse failed");
-    let algebrized = algebrize(&schema, parsed).expect("algebrize failed");
+    let algebrized = algebrize(known, parsed).expect("algebrize failed");
 
     // This query cannot return results: the ident doesn't resolve for a ref-typed attribute.
     assert!(algebrized.is_known_empty());

src/cache.rs

@@ -1,221 +0,0 @@
-// Copyright 2016 Mozilla
-//
-// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
-// this file except in compliance with the License. You may obtain a copy of the
-// License at http://www.apache.org/licenses/LICENSE-2.0
-// Unless required by applicable law or agreed to in writing, software distributed
-// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
-// CONDITIONS OF ANY KIND, either express or implied. See the License for the
-// specific language governing permissions and limitations under the License.
-
-use std::collections::BTreeMap;
-
-use rusqlite;
-
-use mentat_core::{
-    Entid,
-    TypedValue,
-};
-
-use mentat_db::cache::{
-    AttributeValueProvider,
-    Cacheable,
-    EagerCache,
-    CacheMap,
-};
-
-use errors::{
-    Result,
-};
-
-pub enum CacheAction {
-    Register,
-    Deregister,
-}
-
-#[derive(Clone)]
-pub struct AttributeCacher {
-    a_e_vs_cache: BTreeMap<Entid, EagerCache<Entid, Vec<TypedValue>, AttributeValueProvider>>,   // values keyed by attribute
-}
-
-impl AttributeCacher {
-
-    pub fn new() -> Self {
-        AttributeCacher {
-            a_e_vs_cache: BTreeMap::new(),
-        }
-    }
-
-    pub fn register_attribute<'sqlite>(&mut self, sqlite: &'sqlite rusqlite::Connection, attribute: Entid) -> Result<()> {
-        let value_provider = AttributeValueProvider{ attribute: attribute };
-        let mut cacher = EagerCache::new(value_provider);
-        cacher.cache_values(sqlite)?;
-        self.a_e_vs_cache.insert(attribute, cacher);
-        Ok(())
-    }
-
-    pub fn deregister_attribute(&mut self, attribute: &Entid) -> Option<CacheMap<Entid, Vec<TypedValue>>> {
-        self.a_e_vs_cache.remove(&attribute).map(|m| m.cache)
-    }
-
-    pub fn get(&self, attribute: &Entid) -> Option<&CacheMap<Entid, Vec<TypedValue>>> {
-        self.a_e_vs_cache.get( &attribute ).map(|m| &m.cache)
-    }
-
-    pub fn get_values_for_entid(&self, attribute: &Entid, entid: &Entid) -> Option<&Vec<TypedValue>> {
-        self.a_e_vs_cache.get(&attribute).and_then(|c| c.get(&entid))
-    }
-
-    pub fn get_value_for_entid(&self, attribute: &Entid, entid: &Entid) -> Option<&TypedValue> {
-        self.get_values_for_entid(attribute, entid).and_then(|c| c.first())
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use std::rc::Rc;
-    use mentat_core::{
-        HasSchema,
-        KnownEntid,
-    };
-    use mentat_db::db;
-    use mentat_db::types::TypedValue;
-
-    use conn::Conn;
-
-    fn populate_db() -> (Conn, rusqlite::Connection) {
-        let mut sqlite = db::new_connection("").unwrap();
-        let mut conn = Conn::connect(&mut sqlite).unwrap();
-        let _report = conn.transact(&mut sqlite, r#"[
-            {  :db/ident       :foo/bar
-               :db/valueType   :db.type/long
-               :db/cardinality :db.cardinality/one },
-            {  :db/ident       :foo/baz
-               :db/valueType   :db.type/boolean
-               :db/cardinality :db.cardinality/one },
-            {  :db/ident       :foo/bap
-               :db/valueType   :db.type/string
-               :db/cardinality :db.cardinality/many}]"#).expect("transaction expected to succeed");
-        let _report = conn.transact(&mut sqlite, r#"[
-            {  :foo/bar        100
-               :foo/baz        false
-               :foo/bap        ["one","two","buckle my shoe"] },
-            {  :foo/bar        200
-               :foo/baz        true
-               :foo/bap        ["three", "four", "knock at my door"] }]"#).expect("transaction expected to succeed");
-        (conn, sqlite)
-    }
-
-    fn assert_values_present_for_attribute(attribute_cache: &mut AttributeCacher, attribute: &KnownEntid, values: Vec<Vec<TypedValue>>) {
-        let cached_values: Vec<Vec<TypedValue>> = attribute_cache.get(&attribute.0)
-            .expect("Expected cached values")
-            .values()
-            .cloned()
-            .collect();
-        assert_eq!(cached_values, values);
-    }
-
-    #[test]
-    fn test_add_to_cache() {
-        let (conn, sqlite) = populate_db();
-        let schema = conn.current_schema();
-        let mut attribute_cache = AttributeCacher::new();
-        let kw = kw!(:foo/bar);
-        let entid = schema.get_entid(&kw).expect("Expected entid for attribute");
-        attribute_cache.register_attribute(&sqlite, entid.0.clone() ).expect("No errors on add to cache");
-        assert_values_present_for_attribute(&mut attribute_cache, &entid, vec![vec![TypedValue::Long(100)], vec![TypedValue::Long(200)]]);
-    }
-
-    #[test]
-    fn test_add_attribute_already_in_cache() {
-        let (conn, mut sqlite) = populate_db();
-        let schema = conn.current_schema();
-
-        let kw = kw!(:foo/bar);
-        let entid = schema.get_entid(&kw).expect("Expected entid for attribute");
-        let mut attribute_cache = AttributeCacher::new();
-
-        attribute_cache.register_attribute(&mut sqlite, entid.0.clone()).expect("No errors on add to cache");
-        assert_values_present_for_attribute(&mut attribute_cache, &entid, vec![vec![TypedValue::Long(100)], vec![TypedValue::Long(200)]]);
-        attribute_cache.register_attribute(&mut sqlite, entid.0.clone()).expect("No errors on add to cache");
-        assert_values_present_for_attribute(&mut attribute_cache, &entid, vec![vec![TypedValue::Long(100)], vec![TypedValue::Long(200)]]);
-    }
-
-    #[test]
-    fn test_remove_from_cache() {
-        let (conn, mut sqlite) = populate_db();
-        let schema = conn.current_schema();
-
-        let kwr = kw!(:foo/bar);
-        let entidr = schema.get_entid(&kwr).expect("Expected entid for attribute");
-        let kwz = kw!(:foo/baz);
-        let entidz = schema.get_entid(&kwz).expect("Expected entid for attribute");
-
-        let mut attribute_cache = AttributeCacher::new();
-
-        attribute_cache.register_attribute(&mut sqlite, entidr.0.clone()).expect("No errors on add to cache");
-        assert_values_present_for_attribute(&mut attribute_cache, &entidr, vec![vec![TypedValue::Long(100)], vec![TypedValue::Long(200)]]);
-        attribute_cache.register_attribute(&mut sqlite, entidz.0.clone()).expect("No errors on add to cache");
-        assert_values_present_for_attribute(&mut attribute_cache, &entidz, vec![vec![TypedValue::Boolean(false)], vec![TypedValue::Boolean(true)]]);
-
-        // test that we can remove an item from cache
-        attribute_cache.deregister_attribute(&entidz.0).expect("No errors on remove from cache");
-        assert_eq!(attribute_cache.get(&entidz.0), None);
-    }
-
-    #[test]
-    fn test_remove_attribute_not_in_cache() {
-        let (conn, _sqlite) = populate_db();
-        let mut attribute_cache = AttributeCacher::new();
-
-        let schema = conn.current_schema();
-        let kw = kw!(:foo/baz);
-        let entid = schema.get_entid(&kw).expect("Expected entid for attribute").0;
-        assert_eq!(None, attribute_cache.deregister_attribute(&entid));
-    }
-
-    #[test]
-    fn test_fetch_attribute_value_for_entid() {
-        let (conn, mut sqlite) = populate_db();
-        let schema = conn.current_schema();
-
-        let entities = conn.q_once(&sqlite, r#"[:find ?e . :where [?e :foo/bar 100]]"#, None).expect("Expected query to work").into_scalar().expect("expected scalar results");
-        let entid = match entities {
-            Some(TypedValue::Ref(entid)) => entid,
-            x => panic!("expected Some(Ref), got {:?}", x),
-        };
-
-        let kwr = kw!(:foo/bar);
-        let attr_entid = schema.get_entid(&kwr).expect("Expected entid for attribute").0;
-
-        let mut attribute_cache = AttributeCacher::new();
-
-        attribute_cache.register_attribute(&mut sqlite, attr_entid.clone()).expect("No errors on add to cache");
-        let val = attribute_cache.get_value_for_entid(&attr_entid, &entid).expect("Expected value");
-        assert_eq!(*val, TypedValue::Long(100));
-    }
-
-    #[test]
-    fn test_fetch_attribute_values_for_entid() {
-        let (conn, mut sqlite) = populate_db();
-        let schema = conn.current_schema();
-
-        let entities = conn.q_once(&sqlite, r#"[:find ?e . :where [?e :foo/bar 100]]"#, None).expect("Expected query to work").into_scalar().expect("expected scalar results");
-        let entid = match entities {
-            Some(TypedValue::Ref(entid)) => entid,
-            x => panic!("expected Some(Ref), got {:?}", x),
-        };
-
-        let kwp = kw!(:foo/bap);
-        let attr_entid = schema.get_entid(&kwp).expect("Expected entid for attribute").0;
-
-        let mut attribute_cache = AttributeCacher::new();
-
-        attribute_cache.register_attribute(&mut sqlite, attr_entid.clone()).expect("No errors on add to cache");
-        let val = attribute_cache.get_values_for_entid(&attr_entid, &entid).expect("Expected value");
-        assert_eq!(*val, vec![TypedValue::String(Rc::new("buckle my shoe".to_string())), TypedValue::String(Rc::new("one".to_string())), TypedValue::String(Rc::new("two".to_string()))]);
-    }
-}
-
-

src/conn.rs

@@ -42,6 +42,7 @@ use mentat_core::{
 
 use mentat_core::intern_set::InternSet;
 
+use mentat_db::cache::SQLiteAttributeCache;
 use mentat_db::db;
 use mentat_db::{
     transact,
@@ -61,13 +62,6 @@ use mentat_tx_parser;
 use mentat_tolstoy::Syncer;
 
 use uuid::Uuid;
-use cache::{
-    AttributeCacher,
-};
-
-pub use cache::{
-    CacheAction,
-};
 
 use entity_builder::{
     InProgressBuilder,
@@ -76,15 +70,17 @@ use entity_builder::{
 use errors::*;
 
 use query::{
-    lookup_value_for_attribute,
+    Known,
-    lookup_values_for_attribute,
     PreparedResult,
-    q_once,
-    q_prepare,
-    q_explain,
     QueryExplanation,
     QueryInputs,
     QueryOutput,
+    lookup_value_for_attribute,
+    lookup_values_for_attribute,
+    q_explain,
+    q_once,
+    q_prepare,
+    q_uncached,
 };
 
 /// Connection metadata required to query from, or apply transactions to, a Mentat store.
@@ -127,7 +123,7 @@ pub struct Conn {
     // TODO: maintain cache of query plans that could be shared across threads and invalidated when
     // the schema changes. #315.
 
-    attribute_cache: RwLock<AttributeCacher>,
+    attribute_cache: RwLock<SQLiteAttributeCache>,
 }
 
 /// A convenience wrapper around a single SQLite connection and a Conn. This is suitable
@@ -190,7 +186,9 @@ pub struct InProgress<'a, 'c> {
     generation: u64,
     partition_map: PartitionMap,
     schema: Schema,
-    cache: RwLockWriteGuard<'a, AttributeCacher>,
+    cache: RwLockWriteGuard<'a, SQLiteAttributeCache>,
+
+    use_caching: bool,
 }
 
 /// Represents an in-progress set of reads to the store. Just like `InProgress`,
@@ -228,39 +226,50 @@ impl<'a, 'c> Queryable for InProgress<'a, 'c> {
     fn q_once<T>(&self, query: &str, inputs: T) -> Result<QueryOutput>
         where T: Into<Option<QueryInputs>> {
 
+        if self.use_caching {
+            let known = Known::new(&self.schema, Some(&*self.cache));
             q_once(&*(self.transaction),
+                   known,
+                   query,
+                   inputs)
+        } else {
+            q_uncached(&*(self.transaction),
                        &self.schema,
                        query,
                        inputs)
         }
+    }
 
     fn q_prepare<T>(&self, query: &str, inputs: T) -> PreparedResult
         where T: Into<Option<QueryInputs>> {
 
+        let known = Known::new(&self.schema, Some(&*self.cache));
         q_prepare(&*(self.transaction),
-                  &self.schema,
+                  known,
                   query,
                   inputs)
     }
 
     fn q_explain<T>(&self, query: &str, inputs: T) -> Result<QueryExplanation>
         where T: Into<Option<QueryInputs>> {
+
+        let known = Known::new(&self.schema, Some(&*self.cache));
         q_explain(&*(self.transaction),
-                  &self.schema,
+                  known,
                   query,
                   inputs)
     }
 
     fn lookup_values_for_attribute<E>(&self, entity: E, attribute: &edn::NamespacedKeyword) -> Result<Vec<TypedValue>>
         where E: Into<Entid> {
-        let cc = &*self.cache;
+        let known = Known::new(&self.schema, Some(&*self.cache));
-        lookup_values_for_attribute(&*(self.transaction), &self.schema, cc, entity, attribute)
+        lookup_values_for_attribute(&*(self.transaction), known, entity, attribute)
     }
 
     fn lookup_value_for_attribute<E>(&self, entity: E, attribute: &edn::NamespacedKeyword) -> Result<Option<TypedValue>>
         where E: Into<Entid> {
-        let cc = &*self.cache;
+        let known = Known::new(&self.schema, Some(&*self.cache));
-        lookup_value_for_attribute(&*(self.transaction), &self.schema, cc, entity, attribute)
+        lookup_value_for_attribute(&*(self.transaction), known, entity, attribute)
     }
 }
 
@@ -334,6 +343,11 @@ impl<'a, 'c> InProgress<'a, 'c> {
         InProgressBuilder::new(self)
     }
 
+    /// Choose whether to use in-memory caches for running queries.
+    pub fn use_caching(&mut self, yesno: bool) {
+        self.use_caching = yesno;
+    }
+
     pub fn transact_terms<I>(&mut self, terms: I, tempid_set: InternSet<TempId>) -> Result<TxReport> where I: IntoIterator<Item=TermWithTempIds> {
         let (report, next_partition_map, next_schema) = transact_terms(&self.transaction,
                                                                        self.partition_map.clone(),
@@ -405,6 +419,13 @@ impl<'a, 'c> InProgress<'a, 'c> {
     }
 }
 
+impl Store {
+    /// Intended for use from tests.
+    pub fn sqlite_mut(&mut self) -> &mut rusqlite::Connection {
+        &mut self.sqlite
+    }
+}
+
 impl Store {
     pub fn dismantle(self) -> (rusqlite::Connection, Conn) {
         (self.sqlite, self.conn)
@@ -421,6 +442,15 @@ impl Store {
     pub fn begin_transaction<'m>(&'m mut self) -> Result<InProgress<'m, 'm>> {
         self.conn.begin_transaction(&mut self.sqlite)
     }
+
+    pub fn cache(&mut self, attr: &NamespacedKeyword, direction: CacheDirection) -> Result<()> {
+        let schema = &self.conn.current_schema();
+        self.conn.cache(&mut self.sqlite,
+                        schema,
+                        attr,
+                        direction,
+                        CacheAction::Register)
+    }
 }
 
 impl Queryable for Store {
@@ -450,6 +480,19 @@ impl Queryable for Store {
     }
 }
 
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum CacheDirection {
+    Forward,
+    Reverse,
+    Both,
+}
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum CacheAction {
+    Register,
+    Deregister,
+}
+
 impl Syncable for Store {
     fn sync(&mut self, server_uri: &String, user_uuid: &String) -> Result<()> {
         let uuid = Uuid::parse_str(&user_uuid)?;
@@ -462,7 +505,7 @@ impl Conn {
     fn new(partition_map: PartitionMap, schema: Schema) -> Conn {
         Conn {
             metadata: Mutex::new(Metadata::new(0, partition_map, Arc::new(schema))),
-            attribute_cache: RwLock::new(AttributeCacher::new())
+            attribute_cache: Default::default()
         }
     }
 
@@ -500,10 +543,15 @@ impl Conn {
         self.metadata.lock().unwrap().schema.clone()
     }
 
-    pub fn attribute_cache<'s>(&'s self) -> RwLockReadGuard<'s, AttributeCacher> {
+    pub fn attribute_cache<'s>(&'s self) -> RwLockReadGuard<'s, SQLiteAttributeCache> {
         self.attribute_cache.read().unwrap()
     }
 
+    pub fn attribute_cache_mut<'s>(&'s self) -> RwLockWriteGuard<'s, SQLiteAttributeCache> {
+        self.attribute_cache.write().unwrap()
+    }
+
+
     /// Query the Mentat store, using the given connection and the current metadata.
     pub fn q_once<T>(&self,
                      sqlite: &rusqlite::Connection,
@@ -511,8 +559,26 @@ impl Conn {
                      inputs: T) -> Result<QueryOutput>
         where T: Into<Option<QueryInputs>> {
 
+        // Doesn't clone, unlike `current_schema`.
         let metadata = self.metadata.lock().unwrap();
+        let cache = &*self.attribute_cache.read().unwrap();
+        let known = Known::new(&*metadata.schema, Some(cache));
         q_once(sqlite,
+               known,
+               query,
+               inputs)
+    }
+
+    /// Query the Mentat store, using the given connection and the current metadata,
+    /// but without using the cache.
+    pub fn q_uncached<T>(&self,
+                         sqlite: &rusqlite::Connection,
+                         query: &str,
+                         inputs: T) -> Result<QueryOutput>
+        where T: Into<Option<QueryInputs>> {
+
+        let metadata = self.metadata.lock().unwrap();
+        q_uncached(sqlite,
                    &*metadata.schema,        // Doesn't clone, unlike `current_schema`.
                    query,
                    inputs)
@@ -525,8 +591,10 @@ impl Conn {
         where T: Into<Option<QueryInputs>> {
 
         let metadata = self.metadata.lock().unwrap();
+        let cache = &*self.attribute_cache.read().unwrap();
+        let known = Known::new(&*metadata.schema, Some(cache));
         q_prepare(sqlite,
-                  &*metadata.schema,
+                  known,
                   query,
                   inputs)
     }
@@ -537,23 +605,33 @@ impl Conn {
                         inputs: T) -> Result<QueryExplanation>
         where T: Into<Option<QueryInputs>>
     {
-        q_explain(sqlite, &*self.current_schema(), query, inputs)
+        let metadata = self.metadata.lock().unwrap();
+        let cache = &*self.attribute_cache.read().unwrap();
+        let known = Known::new(&*metadata.schema, Some(cache));
+        q_explain(sqlite,
+                  known,
+                  query,
+                  inputs)
     }
 
     pub fn lookup_values_for_attribute(&self,
                                        sqlite: &rusqlite::Connection,
                                        entity: Entid,
                                        attribute: &edn::NamespacedKeyword) -> Result<Vec<TypedValue>> {
-        let cc: &AttributeCacher = &*self.attribute_cache();
+        let schema = &*self.current_schema();
-        lookup_values_for_attribute(sqlite, &*self.current_schema(), cc, entity, attribute)
+        let cache = &*self.attribute_cache();
+        let known = Known::new(schema, Some(cache));
+        lookup_values_for_attribute(sqlite, known, entity, attribute)
     }
 
     pub fn lookup_value_for_attribute(&self,
                                       sqlite: &rusqlite::Connection,
                                       entity: Entid,
                                       attribute: &edn::NamespacedKeyword) -> Result<Option<TypedValue>> {
-        let cc: &AttributeCacher = &*self.attribute_cache();
+        let schema = &*self.current_schema();
-        lookup_value_for_attribute(sqlite, &*self.current_schema(), cc, entity, attribute)
+        let cache = &*self.attribute_cache();
+        let known = Known::new(schema, Some(cache));
+        lookup_value_for_attribute(sqlite, known, entity, attribute)
     }
 
     /// Take a SQLite transaction.
@@ -577,6 +655,7 @@ impl Conn {
             partition_map: current_partition_map,
             schema: (*current_schema).clone(),
             cache: self.attribute_cache.write().unwrap(),
+            use_caching: true,
         })
     }
 
@@ -587,6 +666,14 @@ impl Conn {
             .map(InProgressRead)
     }
 
+    pub fn begin_uncached_read<'m, 'conn>(&'m mut self, sqlite: &'conn mut rusqlite::Connection) -> Result<InProgressRead<'m, 'conn>> {
+        self.begin_transaction_with_behavior(sqlite, TransactionBehavior::Deferred)
+            .map(|mut ip| {
+                ip.use_caching(false);
+                InProgressRead(ip)
+            })
+    }
+
     /// IMMEDIATE means 'start the transaction now, but don't exclude readers'. It prevents other
     /// connections from taking immediate or exclusive transactions. This is appropriate for our
     /// writes and `InProgress`: it means we are ready to write whenever we want to, and nobody else
@@ -628,18 +715,29 @@ impl Conn {
     /// CacheType::Lazy caches values only after they have first been fetched.
     pub fn cache(&mut self,
                  sqlite: &mut rusqlite::Connection,
+                 schema: &Schema,
                  attribute: &NamespacedKeyword,
+                 cache_direction: CacheDirection,
                  cache_action: CacheAction) -> Result<()> {
-        // fetch the attribute for the given name
+        match self.current_schema().attribute_for_ident(&attribute) {
-        let schema = self.current_schema();
+            None => bail!(ErrorKind::UnknownAttribute(attribute.to_string())),
-
+            Some((_attribute, attribute_entid)) => {
                 let mut cache = self.attribute_cache.write().unwrap();
-        let attribute_entid = schema.get_entid(&attribute).ok_or_else(|| ErrorKind::UnknownAttribute(attribute.to_string()))?;
                 match cache_action {
-            CacheAction::Register => { cache.register_attribute(sqlite, attribute_entid.0)?; },
+                    CacheAction::Register => {
-            CacheAction::Deregister => { cache.deregister_attribute(&attribute_entid.0); },
+                        match cache_direction {
-        }
+                            CacheDirection::Both => cache.register(schema, sqlite, attribute_entid),
+                            CacheDirection::Forward => cache.register_forward(schema, sqlite, attribute_entid),
+                            CacheDirection::Reverse => cache.register_reverse(schema, sqlite, attribute_entid),
+                        }.map_err(|e| e.into())
+                    },
+                    CacheAction::Deregister => {
+                        cache.unregister(attribute_entid);
                         Ok(())
+                    },
+                }
+            },
+        }
     }
 }
 
@@ -899,7 +997,8 @@ mod tests {
                :db/valueType   :db.type/boolean }]"#).unwrap();
 
         let kw = kw!(:foo/bat);
-        let res = conn.cache(&mut sqlite,&kw, CacheAction::Register);
+        let schema = conn.current_schema();
+        let res = conn.cache(&mut sqlite, &schema, &kw, CacheDirection::Forward, CacheAction::Register);
         match res.unwrap_err() {
             Error(ErrorKind::UnknownAttribute(msg), _) => assert_eq!(msg, ":foo/bat"),
             x => panic!("expected UnknownAttribute error, got {:?}", x),
@@ -952,7 +1051,8 @@ mod tests {
         let uncached_elapsed_time = finish.duration_since(start);
         println!("Uncached time: {:?}", uncached_elapsed_time);
 
-        conn.cache(&mut sqlite, &kw, CacheAction::Register).expect("expected caching to work");
+        let schema = conn.current_schema();
+        conn.cache(&mut sqlite, &schema, &kw, CacheDirection::Forward, CacheAction::Register).expect("expected caching to work");
 
         for _ in 1..5 {
             let start = Instant::now();

src/lib.rs

@@ -39,6 +39,7 @@ pub use mentat_core::{
     HasSchema,
     KnownEntid,
     NamespacedKeyword,
+    Schema,
     TypedValue,
     Uuid,
     ValueType,
@@ -87,7 +88,6 @@ macro_rules! kw {
     };
 }
 
-pub mod cache;
 pub mod errors;
 pub mod ident;
 pub mod vocabulary;
@@ -95,10 +95,6 @@ pub mod conn;
 pub mod query;
 pub mod entity_builder;
 
-pub fn get_name() -> String {
-    return String::from("mentat");
-}
-
 pub use query::{
     IntoResult,
     PlainSymbol,
@@ -113,6 +109,8 @@ pub use query::{
 };
 
 pub use conn::{
+    CacheAction,
+    CacheDirection,
     Conn,
     InProgress,
     Metadata,

src/query.rs

@@ -23,8 +23,8 @@ use mentat_core::{
 
 use mentat_query_algebrizer::{
     AlgebraicQuery,
-    algebrize_with_inputs,
     EmptyBecause,
+    algebrize_with_inputs,
 };
 
 pub use mentat_query_algebrizer::{
@@ -63,6 +63,10 @@ use mentat_query_translator::{
     query_to_select,
 };
 
+pub use mentat_query_algebrizer::{
+    Known,
+};
+
 pub use mentat_query_projector::{
     QueryOutput,        // Includes the columns/find spec.
     QueryResults,       // The results themselves.
@@ -73,10 +77,6 @@ use errors::{
     Result,
 };
 
-use cache::{
-    AttributeCacher,
-};
-
 pub type QueryExecutionResult = Result<QueryOutput>;
 pub type PreparedResult<'sqlite> = Result<PreparedQuery<'sqlite>>;
 
@@ -154,13 +154,13 @@ pub struct QueryPlanStep {
     pub detail: String,
 }
 
-fn algebrize_query<'schema, T>
+fn algebrize_query<T>
-(schema: &'schema Schema,
+(known: Known,
  query: FindQuery,
  inputs: T) -> Result<AlgebraicQuery>
     where T: Into<Option<QueryInputs>>
 {
-    let algebrized = algebrize_with_inputs(schema, query, 0, inputs.into().unwrap_or(QueryInputs::default()))?;
+    let algebrized = algebrize_with_inputs(known, query, 0, inputs.into().unwrap_or(QueryInputs::default()))?;
     let unbound = algebrized.unbound_variables();
     // Because we are running once, we can check that all of our `:in` variables are bound at this point.
     // If they aren't, the user has made an error -- perhaps writing the wrong variable in `:in`, or
@@ -171,9 +171,9 @@ fn algebrize_query<'schema, T>
     Ok(algebrized)
 }
 
-fn fetch_values<'sqlite, 'schema>
+fn fetch_values<'sqlite>
 (sqlite: &'sqlite rusqlite::Connection,
- schema: &'schema Schema,
+ known: Known,
  entity: Entid,
  attribute: Entid,
  only_one: bool) -> QueryExecutionResult {
@@ -192,7 +192,7 @@ fn fetch_values<'sqlite, 'schema>
     let query = FindQuery::simple(spec,
                                   vec![WhereClause::Pattern(pattern)]);
 
-    let algebrized = algebrize_query(schema, query, None)?;
+    let algebrized = algebrize_query(known, query, None)?;
 
     run_algebrized_query(sqlite, algebrized)
 }
@@ -208,57 +208,62 @@ fn lookup_attribute(schema: &Schema, attribute: &NamespacedKeyword) -> Result<Kn
 /// If `attribute` isn't an attribute, `None` is returned.
 pub fn lookup_value<'sqlite, 'schema, 'cache, E, A>
 (sqlite: &'sqlite rusqlite::Connection,
- schema: &'schema Schema,
+ known: Known,
- cache: &'cache AttributeCacher,
  entity: E,
  attribute: A) -> Result<Option<TypedValue>>
- where E: Into<Entid>, A: Into<Entid> {
+ where E: Into<Entid>,
+       A: Into<Entid> {
     let entid = entity.into();
     let attrid = attribute.into();
-    let cached = cache.get_value_for_entid(&attrid, &entid).cloned();
+
-    if cached.is_some() {
+    if known.is_attribute_cached_forward(attrid) {
-        return Ok(cached);
+        Ok(known.get_value_for_entid(known.schema, attrid, entid).cloned())
+    } else {
+        fetch_values(sqlite, known, entid, attrid, true).into_scalar_result()
     }
-    fetch_values(sqlite, schema, entid, attrid, true).into_scalar_result()
 }
 
-pub fn lookup_values<'sqlite, 'schema, 'cache, E, A>
+pub fn lookup_values<'sqlite, E, A>
 (sqlite: &'sqlite rusqlite::Connection,
- schema: &'schema Schema,
+ known: Known,
- cache: &'cache AttributeCacher,
  entity: E,
  attribute: A) -> Result<Vec<TypedValue>>
- where E: Into<Entid>, A: Into<Entid> {
+ where E: Into<Entid>,
+       A: Into<Entid> {
     let entid = entity.into();
     let attrid = attribute.into();
-    if let Some(cached) = cache.get_values_for_entid(&attrid, &entid).cloned() {
+
-        return Ok(cached);
+    if known.is_attribute_cached_forward(attrid) {
+        Ok(known.get_values_for_entid(known.schema, attrid, entid)
+                .cloned()
+                .unwrap_or_else(|| vec![]))
+    } else {
+        fetch_values(sqlite, known, entid, attrid, false).into_coll_result()
     }
-    fetch_values(sqlite, schema, entid, attrid, false).into_coll_result()
 }
 
 /// Return a single value for the provided entity and attribute.
 /// If the attribute is multi-valued, an arbitrary value is returned.
 /// If no value is present for that entity, `None` is returned.
 /// If `attribute` doesn't name an attribute, an error is returned.
-pub fn lookup_value_for_attribute<'sqlite, 'schema, 'cache, 'attribute, E>
+pub fn lookup_value_for_attribute<'sqlite, 'attribute, E>
 (sqlite: &'sqlite rusqlite::Connection,
- schema: &'schema Schema,
+ known: Known,
- cache: &'cache AttributeCacher,
  entity: E,
  attribute: &'attribute NamespacedKeyword) -> Result<Option<TypedValue>>
  where E: Into<Entid> {
-    lookup_value(sqlite, schema, cache, entity.into(), lookup_attribute(schema, attribute)?)
+    let attribute = lookup_attribute(known.schema, attribute)?;
+    lookup_value(sqlite, known, entity.into(), attribute)
 }
 
-pub fn lookup_values_for_attribute<'sqlite, 'schema, 'cache, 'attribute, E>
+pub fn lookup_values_for_attribute<'sqlite, 'attribute, E>
 (sqlite: &'sqlite rusqlite::Connection,
- schema: &'schema Schema,
+ known: Known,
- cache: &'cache AttributeCacher,
  entity: E,
  attribute: &'attribute NamespacedKeyword) -> Result<Vec<TypedValue>>
  where E: Into<Entid> {
-    lookup_values(sqlite, schema, cache, entity.into(), lookup_attribute(schema, attribute)?)
+    let attribute = lookup_attribute(known.schema, attribute)?;
+    lookup_values(sqlite, known, entity.into(), attribute)
 }
 
 fn run_statement<'sqlite, 'stmt, 'bound>
@@ -293,14 +298,13 @@ fn run_sql_query<'sqlite, 'sql, 'bound, T, F>
     Ok(result)
 }
 
-fn algebrize_query_str<'schema, 'query, T>
+fn algebrize_query_str<'query, T>
-(schema: &'schema Schema,
+(known: Known,
  query: &'query str,
  inputs: T) -> Result<AlgebraicQuery>
-    where T: Into<Option<QueryInputs>>
+    where T: Into<Option<QueryInputs>> {
-{
     let parsed = parse_find_string(query)?;
-    algebrize_query(schema, parsed, inputs)
+    algebrize_query(known, parsed, inputs)
 }
 
 fn run_algebrized_query<'sqlite>(sqlite: &'sqlite rusqlite::Connection, algebrized: AlgebraicQuery) -> QueryExecutionResult {
@@ -329,26 +333,39 @@ fn run_algebrized_query<'sqlite>(sqlite: &'sqlite rusqlite::Connection, algebriz
 /// instances.
 /// The caller is responsible for ensuring that the SQLite connection has an open transaction if
 /// isolation is required.
-pub fn q_once<'sqlite, 'schema, 'query, T>
+pub fn q_once<'sqlite, 'query, T>
+(sqlite: &'sqlite rusqlite::Connection,
+ known: Known,
+ query: &'query str,
+ inputs: T) -> QueryExecutionResult
+        where T: Into<Option<QueryInputs>>
+{
+    let algebrized = algebrize_query_str(known, query, inputs)?;
+    run_algebrized_query(sqlite, algebrized)
+}
+
+/// Just like `q_once`, but doesn't use any cached values.
+pub fn q_uncached<'sqlite, 'schema, 'query, T>
 (sqlite: &'sqlite rusqlite::Connection,
  schema: &'schema Schema,
  query: &'query str,
  inputs: T) -> QueryExecutionResult
         where T: Into<Option<QueryInputs>>
 {
-    let algebrized = algebrize_query_str(schema, query, inputs)?;
+    let known = Known::for_schema(schema);
+    let algebrized = algebrize_query_str(known, query, inputs)?;
 
     run_algebrized_query(sqlite, algebrized)
 }
 
-pub fn q_prepare<'sqlite, 'schema, 'query, T>
+pub fn q_prepare<'sqlite, 'query, T>
 (sqlite: &'sqlite rusqlite::Connection,
- schema: &'schema Schema,
+ known: Known,
  query: &'query str,
  inputs: T) -> PreparedResult<'sqlite>
         where T: Into<Option<QueryInputs>>
 {
-    let algebrized = algebrize_query_str(schema, query, inputs)?;
+    let algebrized = algebrize_query_str(known, query, inputs)?;
 
     let unbound = algebrized.unbound_variables();
     if !unbound.is_empty() {
@@ -375,14 +392,14 @@ pub fn q_prepare<'sqlite, 'schema, 'query, T>
     })
 }
 
-pub fn q_explain<'sqlite, 'schema, 'query, T>
+pub fn q_explain<'sqlite, 'query, T>
 (sqlite: &'sqlite rusqlite::Connection,
- schema: &'schema Schema,
+ known: Known,
  query: &'query str,
  inputs: T) -> Result<QueryExplanation>
         where T: Into<Option<QueryInputs>>
 {
-    let algebrized = algebrize_query_str(schema, query, inputs)?;
+    let algebrized = algebrize_query_str(known, query, inputs)?;
     if algebrized.is_known_empty() {
         return Ok(QueryExplanation::KnownEmpty(algebrized.cc.empty_because.unwrap()));
     }

tests/cache.rs

@@ -0,0 +1,225 @@
+// Copyright 2016 Mozilla
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not use
+// this file except in compliance with the License. You may obtain a copy of the
+// License at http://www.apache.org/licenses/LICENSE-2.0
+// Unless required by applicable law or agreed to in writing, software distributed
+// under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+// CONDITIONS OF ANY KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations under the License.
+
+extern crate rusqlite;
+
+#[macro_use]
+extern crate mentat;
+extern crate mentat_core;
+extern crate mentat_db;
+
+use std::collections::BTreeSet;
+
+use mentat_core::{
+    CachedAttributes,
+};
+
+use mentat::{
+    Entid,
+    HasSchema,
+    Queryable,
+    Schema,
+    Store,
+    TypedValue,
+};
+
+use mentat_db::cache::{
+    SQLiteAttributeCache,
+};
+
+fn populate_db() -> Store {
+    let mut store = Store::open("").expect("opened");
+    {
+        let mut write = store.begin_transaction().expect("began transaction");
+        let _report = write.transact(r#"[
+            {:db/ident       :foo/bar
+             :db/valueType   :db.type/long
+             :db/cardinality :db.cardinality/one },
+            {:db/ident       :foo/baz
+             :db/valueType   :db.type/boolean
+             :db/cardinality :db.cardinality/one },
+            {:db/ident       :foo/bap
+             :db/valueType   :db.type/string
+             :db/cardinality :db.cardinality/many}]"#).expect("transaction expected to succeed");
+        let _report = write.transact(r#"[
+            {:db/ident       :item/one
+             :foo/bar        100
+             :foo/baz        false
+             :foo/bap        ["one","two","buckle my shoe"] },
+            {:db/ident       :item/two
+             :foo/bar        200
+             :foo/baz        true
+             :foo/bap        ["three", "four", "knock at my door"] }]"#).expect("transaction expected to succeed");
+        write.commit().expect("committed");
+    }
+    store
+}
+
+fn assert_value_present_for_attribute(schema: &Schema, attribute_cache: &mut SQLiteAttributeCache, attribute: Entid, entity: Entid, value: TypedValue) {
+    let one = attribute_cache.get_value_for_entid(schema, attribute, entity);
+    assert!(attribute_cache.get_values_for_entid(schema, attribute, entity).is_none());
+
+    assert_eq!(one, Some(&value));
+}
+
+fn assert_values_present_for_attribute(schema: &Schema, attribute_cache: &mut SQLiteAttributeCache, attribute: Entid, entity: Entid, values: Vec<TypedValue>) {
+    assert!(attribute_cache.get_value_for_entid(schema, attribute, entity).is_none());
+    let actual: BTreeSet<TypedValue> = attribute_cache.get_values_for_entid(schema, attribute, entity)
+                                                      .expect("Non-None")
+                                                      .clone()
+                                                      .into_iter()
+                                                      .collect();
+    let expected: BTreeSet<TypedValue> = values.into_iter().collect();
+
+    assert_eq!(actual, expected);
+}
+
+#[test]
+fn test_add_to_cache() {
+    let mut store = populate_db();
+    let schema = &store.conn().current_schema();
+    let mut attribute_cache = SQLiteAttributeCache::default();
+    let kw = kw!(:foo/bar);
+    let attr: Entid = schema.get_entid(&kw).expect("Expected entid for attribute").into();
+
+    {
+        assert!(attribute_cache.value_pairs(schema, attr).is_none());
+    }
+
+    attribute_cache.register(&schema, &store.sqlite_mut(), attr).expect("No errors on add to cache");
+    {
+        let cached_values = attribute_cache.value_pairs(schema, attr).expect("non-None");
+        assert!(!cached_values.is_empty());
+        let flattened: BTreeSet<TypedValue> = cached_values.values().cloned().collect();
+        let expected: BTreeSet<TypedValue> = vec![TypedValue::Long(100), TypedValue::Long(200)].into_iter().collect();
+        assert_eq!(flattened, expected);
+    }
+}
+
+#[test]
+fn test_add_attribute_already_in_cache() {
+    let mut store = populate_db();
+    let schema = store.conn().current_schema();
+
+    let kw = kw!(:foo/bar);
+    let attr: Entid = schema.get_entid(&kw).expect("Expected entid for attribute").into();
+    let mut attribute_cache = SQLiteAttributeCache::default();
+
+    let one = schema.get_entid(&kw!(:item/one)).expect("one");
+    let two = schema.get_entid(&kw!(:item/two)).expect("two");
+    attribute_cache.register(&schema, &mut store.sqlite_mut(), attr).expect("No errors on add to cache");
+    assert_value_present_for_attribute(&schema, &mut attribute_cache, attr.into(), one.into(), TypedValue::Long(100));
+    attribute_cache.register(&schema, &mut store.sqlite_mut(), attr).expect("No errors on add to cache");
+    assert_value_present_for_attribute(&schema, &mut attribute_cache, attr.into(), two.into(), TypedValue::Long(200));
+}
+
+#[test]
+fn test_remove_from_cache() {
+    let mut store = populate_db();
+    let schema = store.conn().current_schema();
+
+    let kwr = kw!(:foo/bar);
+    let entidr: Entid = schema.get_entid(&kwr).expect("Expected entid for attribute").into();
+    let kwz = kw!(:foo/baz);
+    let entidz: Entid = schema.get_entid(&kwz).expect("Expected entid for attribute").into();
+    let kwp = kw!(:foo/bap);
+    let entidp: Entid = schema.get_entid(&kwp).expect("Expected entid for attribute").into();
+
+    let mut attribute_cache = SQLiteAttributeCache::default();
+
+    let one = schema.get_entid(&kw!(:item/one)).expect("one");
+    let two = schema.get_entid(&kw!(:item/two)).expect("two");
+    assert!(attribute_cache.get_value_for_entid(&schema, entidz, one.into()).is_none());
+    assert!(attribute_cache.get_values_for_entid(&schema, entidz, one.into()).is_none());
+    assert!(attribute_cache.get_value_for_entid(&schema, entidz, two.into()).is_none());
+    assert!(attribute_cache.get_values_for_entid(&schema, entidz, two.into()).is_none());
+    assert!(attribute_cache.get_value_for_entid(&schema, entidp, one.into()).is_none());
+    assert!(attribute_cache.get_values_for_entid(&schema, entidp, one.into()).is_none());
+
+    attribute_cache.register(&schema, &mut store.sqlite_mut(), entidr).expect("No errors on add to cache");
+    assert_value_present_for_attribute(&schema, &mut attribute_cache, entidr, one.into(), TypedValue::Long(100));
+    assert_value_present_for_attribute(&schema, &mut attribute_cache, entidr, two.into(), TypedValue::Long(200));
+    attribute_cache.register(&schema, &mut store.sqlite_mut(), entidz).expect("No errors on add to cache");
+    assert_value_present_for_attribute(&schema, &mut attribute_cache, entidz, one.into(), TypedValue::Boolean(false));
+    assert_value_present_for_attribute(&schema, &mut attribute_cache, entidz, one.into(), TypedValue::Boolean(false));
+    attribute_cache.register(&schema, &mut store.sqlite_mut(), entidp).expect("No errors on add to cache");
+    assert_values_present_for_attribute(&schema, &mut attribute_cache, entidp, one.into(),
+        vec![TypedValue::typed_string("buckle my shoe"),
+             TypedValue::typed_string("one"),
+             TypedValue::typed_string("two")]);
+    assert_values_present_for_attribute(&schema, &mut attribute_cache, entidp, two.into(),
+        vec![TypedValue::typed_string("knock at my door"),
+             TypedValue::typed_string("three"),
+             TypedValue::typed_string("four")]);
+
+    // test that we can remove an item from cache
+    attribute_cache.unregister(entidz);
+    assert!(!attribute_cache.is_attribute_cached_forward(entidz.into()));
+    assert!(attribute_cache.get_value_for_entid(&schema, entidz, one.into()).is_none());
+    assert!(attribute_cache.get_values_for_entid(&schema, entidz, one.into()).is_none());
+    assert!(attribute_cache.get_value_for_entid(&schema, entidz, two.into()).is_none());
+    assert!(attribute_cache.get_values_for_entid(&schema, entidz, two.into()).is_none());
+}
+
+#[test]
+fn test_remove_attribute_not_in_cache() {
+    let store = populate_db();
+    let mut attribute_cache = SQLiteAttributeCache::default();
+
+    let schema = store.conn().current_schema();
+    let kw = kw!(:foo/baz);
+    let entid = schema.get_entid(&kw).expect("Expected entid for attribute").0;
+    attribute_cache.unregister(entid);
+    assert!(!attribute_cache.is_attribute_cached_forward(entid));
+}
+
+#[test]
+fn test_fetch_attribute_value_for_entid() {
+    let mut store = populate_db();
+    let schema = store.conn().current_schema();
+
+    let entities = store.q_once(r#"[:find ?e . :where [?e :foo/bar 100]]"#, None).expect("Expected query to work").into_scalar().expect("expected scalar results");
+    let entid = match entities {
+        Some(TypedValue::Ref(entid)) => entid,
+        x => panic!("expected Some(Ref), got {:?}", x),
+    };
+
+    let kwr = kw!(:foo/bar);
+    let attr_entid = schema.get_entid(&kwr).expect("Expected entid for attribute").0;
+
+    let mut attribute_cache = SQLiteAttributeCache::default();
+
+    attribute_cache.register(&schema, &mut store.sqlite_mut(), attr_entid).expect("No errors on add to cache");
+    let val = attribute_cache.get_value_for_entid(&schema, attr_entid, entid).expect("Expected value");
+    assert_eq!(*val, TypedValue::Long(100));
+}
+
+#[test]
+fn test_fetch_attribute_values_for_entid() {
+    let mut store = populate_db();
+    let schema = store.conn().current_schema();
+
+    let entities = store.q_once(r#"[:find ?e . :where [?e :foo/bar 100]]"#, None).expect("Expected query to work").into_scalar().expect("expected scalar results");
+    let entid = match entities {
+        Some(TypedValue::Ref(entid)) => entid,
+        x => panic!("expected Some(Ref), got {:?}", x),
+    };
+
+    let kwp = kw!(:foo/bap);
+    let attr_entid = schema.get_entid(&kwp).expect("Expected entid for attribute").0;
+
+    let mut attribute_cache = SQLiteAttributeCache::default();
+
+    attribute_cache.register(&schema, &mut store.sqlite_mut(), attr_entid).expect("No errors on add to cache");
+    let val = attribute_cache.get_values_for_entid(&schema, attr_entid, entid).expect("Expected value");
+    assert_eq!(*val, vec![TypedValue::typed_string("buckle my shoe"),
+                          TypedValue::typed_string("one"),
+                          TypedValue::typed_string("two")]);
+}

tests/query.rs

@@ -32,15 +32,17 @@ use mentat_core::{
 };
 
 use mentat::{
+    IntoResult,
     NamespacedKeyword,
     PlainSymbol,
     QueryInputs,
     QueryResults,
     Variable,
     new_connection,
-    q_once,
 };
 
+use mentat::query::q_uncached;
+
 use mentat::conn::Conn;
 
 use mentat::errors::{
@@ -55,7 +57,7 @@ fn test_rel() {
 
     // Rel.
     let start = time::PreciseTime::now();
-    let results = q_once(&c, &db.schema,
+    let results = q_uncached(&c, &db.schema,
                              "[:find ?x ?ident :where [?x :db/ident ?ident]]", None)
         .expect("Query failed")
         .results;
@@ -86,7 +88,7 @@ fn test_failing_scalar() {
 
     // Scalar that fails.
     let start = time::PreciseTime::now();
-    let results = q_once(&c, &db.schema,
+    let results = q_uncached(&c, &db.schema,
                              "[:find ?x . :where [?x :db/fulltext true]]", None)
         .expect("Query failed")
         .results;
@@ -109,7 +111,7 @@ fn test_scalar() {
 
     // Scalar that succeeds.
     let start = time::PreciseTime::now();
-    let results = q_once(&c, &db.schema,
+    let results = q_uncached(&c, &db.schema,
                              "[:find ?ident . :where [24 :db/ident ?ident]]", None)
         .expect("Query failed")
         .results;
@@ -137,7 +139,7 @@ fn test_tuple() {
 
     // Tuple.
     let start = time::PreciseTime::now();
-    let results = q_once(&c, &db.schema,
+    let results = q_uncached(&c, &db.schema,
                              "[:find [?index ?cardinality]
                                :where [:db/txInstant :db/index ?index]
                                       [:db/txInstant :db/cardinality ?cardinality]]",
@@ -168,7 +170,7 @@ fn test_coll() {
 
     // Coll.
     let start = time::PreciseTime::now();
-    let results = q_once(&c, &db.schema,
+    let results = q_uncached(&c, &db.schema,
                              "[:find [?e ...] :where [?e :db/ident _]]", None)
         .expect("Query failed")
         .results;
@@ -194,7 +196,7 @@ fn test_inputs() {
     // entids::DB_INSTALL_VALUE_TYPE = 5.
     let ee = (Variable::from_valid_name("?e"), TypedValue::Ref(5));
     let inputs = QueryInputs::with_value_sequence(vec![ee]);
-    let results = q_once(&c, &db.schema,
+    let results = q_uncached(&c, &db.schema,
                              "[:find ?i . :in ?e :where [?e :db/ident ?i]]", inputs)
                         .expect("query to succeed")
                         .results;
@@ -215,7 +217,7 @@ fn test_unbound_inputs() {
     // Bind the wrong var by 'mistake'.
     let xx = (Variable::from_valid_name("?x"), TypedValue::Ref(5));
     let inputs = QueryInputs::with_value_sequence(vec![xx]);
-    let results = q_once(&c, &db.schema,
+    let results = q_uncached(&c, &db.schema,
                              "[:find ?i . :in ?e :where [?e :db/ident ?i]]", inputs);
 
     match results {
@@ -620,3 +622,38 @@ fn test_type_reqs() {
         }
     };
 }
+
+#[test]
+fn test_cache_usage() {
+    let mut c = new_connection("").expect("opened connection");
+    let conn = Conn::connect(&mut c).expect("connected");
+
+    let db_ident = (*conn.current_schema()).get_entid(&kw!(:db/ident)).expect("db_ident");
+    let db_type = (*conn.current_schema()).get_entid(&kw!(:db/valueType)).expect("db_ident");
+    println!("db/ident is {}", db_ident.0);
+    println!("db/type is {}", db_type.0);
+    let query = format!("[:find ?ident . :where [?e {} :db/doc][?e {} ?type][?type {} ?ident]]",
+                        db_ident.0, db_type.0, db_ident.0);
+
+    println!("Query is {}", query);
+
+    let schema = conn.current_schema();
+    (*conn.attribute_cache_mut()).register(&schema, &mut c, db_ident).expect("registered");
+    (*conn.attribute_cache_mut()).register(&schema, &mut c, db_type).expect("registered");
+
+    let ident = conn.q_once(&c, query.as_str(), None).into_scalar_result().expect("query");
+    assert_eq!(ident, Some(TypedValue::typed_ns_keyword("db.type", "string")));
+
+    let ident = conn.q_uncached(&c, query.as_str(), None).into_scalar_result().expect("query");
+    assert_eq!(ident, Some(TypedValue::typed_ns_keyword("db.type", "string")));
+
+    let start = time::PreciseTime::now();
+    conn.q_once(&c, query.as_str(), None).into_scalar_result().expect("query");
+    let end = time::PreciseTime::now();
+    println!("Cached took {}µs", start.to(end).num_microseconds().unwrap());
+
+    let start = time::PreciseTime::now();
+    conn.q_uncached(&c, query.as_str(), None).into_scalar_result().expect("query");
+    let end = time::PreciseTime::now();
+    println!("Uncached took {}µs", start.to(end).num_microseconds().unwrap());
+}

tools/cli/src/mentat_cli/command_parser.rs

@@ -32,9 +32,12 @@ use errors as cli;
 
 use edn;
 
+use mentat::CacheDirection;
+
 pub static HELP_COMMAND: &'static str = &"help";
 pub static OPEN_COMMAND: &'static str = &"open";
 pub static OPEN_EMPTY_COMMAND: &'static str = &"empty";
+pub static CACHE_COMMAND: &'static str = &"cache";
 pub static CLOSE_COMMAND: &'static str = &"close";
 pub static LONG_QUERY_COMMAND: &'static str = &"query";
 pub static SHORT_QUERY_COMMAND: &'static str = &"q";
@@ -55,6 +58,7 @@ pub enum Command {
     Help(Vec<String>),
     Open(String),
     OpenEmpty(String),
+    Cache(String, CacheDirection),
     Query(String),
     Schema,
     Sync(Vec<String>),
@@ -82,6 +86,7 @@ impl Command {
             &Command::Close |
             &Command::Exit |
             &Command::Sync(_) |
+            &Command::Cache(_, _) |
             &Command::Schema => true
         }
     }
@@ -95,6 +100,7 @@ impl Command {
             &Command::Help(_) |
             &Command::Open(_) |
             &Command::OpenEmpty(_) |
+            &Command::Cache(_, _) |
             &Command::Close |
             &Command::Exit |
             &Command::Sync(_) |
@@ -110,6 +116,9 @@ impl Command {
             &Command::Transact(ref args) => {
                 format!(".{} {}", LONG_TRANSACT_COMMAND, args)
             },
+            &Command::Cache(ref attr, ref direction) => {
+                format!(".{} {} {:?}", CACHE_COMMAND, attr, direction)
+            },
             &Command::Timer(on) => {
                 format!(".{} {}", LONG_TIMER_COMMAND, on)
             },
@@ -142,6 +151,7 @@ impl Command {
 }
 
 pub fn command(s: &str) -> Result<Command, cli::Error> {
+    let argument = || many1::<String, _>(satisfy(|c: char| !c.is_whitespace()));
     let arguments = || sep_end_by::<Vec<_>, _, _>(many1(satisfy(|c: char| !c.is_whitespace())), many1::<Vec<_>, _>(space())).expected("arguments");
 
     let help_parser = string(HELP_COMMAND)
@@ -158,6 +168,18 @@ pub fn command(s: &str) -> Result<Command, cli::Error> {
                         Ok(Command::Timer(args))
                     });
 
+    let direction_parser = || string("forward")
+                                .map(|_| CacheDirection::Forward)
+                           .or(string("reverse").map(|_| CacheDirection::Reverse))
+                           .or(string("both").map(|_| CacheDirection::Both));
+
+    let cache_parser = string(CACHE_COMMAND)
+                    .with(spaces())
+                    .with(argument().skip(spaces()).and(direction_parser())
+                    .map(|(arg, direction)| {
+                        Ok(Command::Cache(arg, direction))
+                    }));
+
     let open_parser = string(OPEN_COMMAND)
                     .with(spaces())
                     .with(arguments())
@@ -256,9 +278,10 @@ pub fn command(s: &str) -> Result<Command, cli::Error> {
                         });
     spaces()
     .skip(token('.'))
-    .with(choice::<[&mut Parser<Input = _, Output = Result<Command, cli::Error>>; 11], _>
+    .with(choice::<[&mut Parser<Input = _, Output = Result<Command, cli::Error>>; 12], _>
           ([&mut try(help_parser),
             &mut try(timer_parser),
+            &mut try(cache_parser),
             &mut try(open_parser),
             &mut try(open_empty_parser),
             &mut try(close_parser),

tools/cli/src/mentat_cli/repl.rs

@@ -25,6 +25,8 @@ use time::{
 };
 
 use mentat::{
+    CacheDirection,
+    NamespacedKeyword,
     Queryable,
     QueryExplanation,
     QueryOutput,
@@ -39,6 +41,7 @@ use command_parser::{
     Command,
     HELP_COMMAND,
     OPEN_COMMAND,
+    CACHE_COMMAND,
     LONG_QUERY_COMMAND,
     SHORT_QUERY_COMMAND,
     SCHEMA_COMMAND,
@@ -66,6 +69,7 @@ lazy_static! {
         map.insert(SHORT_EXIT_COMMAND, "Shortcut for `.exit`. Close the current database and exit the REPL.");
         map.insert(HELP_COMMAND, "Show help for commands.");
         map.insert(OPEN_COMMAND, "Open a database at path.");
+        map.insert(CACHE_COMMAND, "Cache an attribute. Usage: `.cache :foo/bar reverse`");
         map.insert(LONG_QUERY_COMMAND, "Execute a query against the current open database.");
         map.insert(SHORT_QUERY_COMMAND, "Shortcut for `.query`. Execute a query against the current open database.");
         map.insert(SCHEMA_COMMAND, "Output the schema for the current open database.");
@@ -83,6 +87,17 @@ fn eprint_out(s: &str) {
     eprint!("{green}{s}{reset}", green = color::Fg(::GREEN), s = s, reset = color::Fg(color::Reset));
 }
 
+fn parse_namespaced_keyword(input: &str) -> Option<NamespacedKeyword> {
+    let splits = [':', '/'];
+    let mut i = input.split(&splits[..]);
+    match (i.next(), i.next(), i.next(), i.next()) {
+        (Some(""), Some(namespace), Some(name), None) => {
+            Some(NamespacedKeyword::new(namespace, name))
+        },
+        _ => None,
+    }
+}
+
 fn format_time(duration: Duration) {
     let m_micros = duration.num_microseconds();
     if let Some(micros) = m_micros {
@@ -168,6 +183,17 @@ impl Repl {
         }
     }
 
+    fn cache(&mut self, attr: String, direction: CacheDirection) {
+        if let Some(kw) = parse_namespaced_keyword(attr.as_str()) {
+            match self.store.cache(&kw, direction) {
+                Result::Ok(_) => (),
+                Result::Err(e) => eprintln!("Couldn't cache attribute: {}", e),
+            };
+        } else {
+            eprintln!("Invalid attribute {}", attr);
+        }
+    }
+
     /// Runs a single command input.
     fn handle_command(&mut self, cmd: Command) {
         let should_time = self.timer_on && cmd.is_timed();
@@ -177,6 +203,7 @@ impl Repl {
         match cmd {
             Command::Help(args) => self.help_command(args),
             Command::Timer(on) => self.toggle_timer(on),
+            Command::Cache(attr, direction) => self.cache(attr, direction),
             Command::Open(db) => {
                 match self.open(db) {
                     Ok(_) => println!("Database {:?} opened", self.db_name()),