mentat/query-projector/src/lib.rs

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// 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.
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extern crate failure;
extern crate indexmap;
extern crate rusqlite;
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extern crate edn;
extern crate mentat_core;
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extern crate db_traits;
#[macro_use]
extern crate core_traits;
extern crate mentat_db; // For value conversion.
extern crate mentat_query_algebrizer;
extern crate mentat_query_pull;
extern crate query_pull_traits;
extern crate query_projector_traits;
extern crate mentat_query_sql;
use std::collections::{
BTreeSet,
};
use std::iter;
use std::rc::Rc;
use rusqlite::{
Row,
Rows,
};
use core_traits::{
Binding,
TypedValue,
};
use mentat_core::{
Schema,
ValueTypeTag,
};
use mentat_core::util::{
Either,
};
use mentat_db::{
TypedSQLValue,
};
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use edn::query::{
Element,
FindSpec,
Limit,
Variable,
};
use mentat_query_algebrizer::{
AlgebraicQuery,
VariableBindings,
};
use mentat_query_sql::{
GroupBy,
Projection,
};
pub mod translate;
mod binding_tuple;
pub use binding_tuple::{
BindingTuple,
};
mod project;
mod projectors;
mod pull;
mod relresult;
use project::{
ProjectedElements,
project_elements,
};
pub use project::{
projected_column_for_var,
};
pub use projectors::{
ConstantProjector,
Projector,
};
use projectors::{
CollProjector,
CollTwoStagePullProjector,
RelProjector,
RelTwoStagePullProjector,
ScalarProjector,
ScalarTwoStagePullProjector,
TupleProjector,
TupleTwoStagePullProjector,
};
pub use relresult::{
RelResult,
StructuredRelResult,
};
use query_projector_traits::errors::{
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ProjectorError,
Result,
};
#[derive(Clone, Debug, PartialEq, Eq)]
pub struct QueryOutput {
pub spec: Rc<FindSpec>,
pub results: QueryResults,
}
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum QueryResults {
Scalar(Option<Binding>),
Tuple(Option<Vec<Binding>>),
Coll(Vec<Binding>),
Rel(RelResult<Binding>),
}
impl From<QueryOutput> for QueryResults {
fn from(o: QueryOutput) -> QueryResults {
o.results
}
}
impl QueryOutput {
pub fn empty_factory(spec: &FindSpec) -> Box<Fn() -> QueryResults> {
use self::FindSpec::*;
match spec {
&FindScalar(_) => Box::new(|| QueryResults::Scalar(None)),
&FindTuple(_) => Box::new(|| QueryResults::Tuple(None)),
&FindColl(_) => Box::new(|| QueryResults::Coll(vec![])),
&FindRel(ref es) => {
let width = es.len();
Box::new(move || QueryResults::Rel(RelResult::empty(width)))
},
}
}
pub fn len(&self) -> usize {
self.results.len()
}
pub fn is_empty(&self) -> bool {
self.results.is_empty()
}
pub fn empty(spec: &Rc<FindSpec>) -> QueryOutput {
use self::FindSpec::*;
let results =
match &**spec {
&FindScalar(_) => QueryResults::Scalar(None),
&FindTuple(_) => QueryResults::Tuple(None),
&FindColl(_) => QueryResults::Coll(vec![]),
&FindRel(ref es) => QueryResults::Rel(RelResult::empty(es.len())),
};
QueryOutput {
spec: spec.clone(),
results: results,
}
}
pub fn from_constants(spec: &Rc<FindSpec>, bindings: VariableBindings) -> QueryResults {
use self::FindSpec::*;
match &**spec {
&FindScalar(Element::Variable(ref var)) |
&FindScalar(Element::Corresponding(ref var)) => {
let val = bindings.get(var)
.cloned()
.map(|v| v.into());
QueryResults::Scalar(val)
},
&FindScalar(Element::Aggregate(ref _agg)) => {
// TODO: static aggregates.
unimplemented!();
},
&FindScalar(Element::Pull(ref _pull)) => {
// TODO: static pull.
unimplemented!();
},
&FindTuple(ref elements) => {
let values = elements.iter()
.map(|e| match e {
&Element::Variable(ref var) |
&Element::Corresponding(ref var) => {
bindings.get(var)
.cloned()
.expect("every var to have a binding")
.into()
},
&Element::Pull(ref _pull) => {
// TODO: static pull.
unreachable!();
},
&Element::Aggregate(ref _agg) => {
// TODO: static computation of aggregates, then
// implement the condition in `is_fully_bound`.
unreachable!();
},
})
.collect();
QueryResults::Tuple(Some(values))
},
&FindColl(Element::Variable(ref var)) |
&FindColl(Element::Corresponding(ref var)) => {
let val = bindings.get(var)
.cloned()
.expect("every var to have a binding")
.into();
QueryResults::Coll(vec![val])
},
&FindColl(Element::Pull(ref _pull)) => {
// TODO: static pull.
unimplemented!();
},
&FindColl(Element::Aggregate(ref _agg)) => {
// Does it even make sense to write
// [:find [(max ?x) ...] :where [_ :foo/bar ?x]]
// ?
// TODO
unimplemented!();
},
&FindRel(ref elements) => {
let width = elements.len();
let values = elements.iter().map(|e| match e {
&Element::Variable(ref var) |
&Element::Corresponding(ref var) => {
bindings.get(var)
.cloned()
.expect("every var to have a binding")
.into()
},
&Element::Pull(ref _pull) => {
// TODO: static pull.
unreachable!();
},
&Element::Aggregate(ref _agg) => {
// TODO: static computation of aggregates, then
// implement the condition in `is_fully_bound`.
unreachable!();
},
}).collect();
QueryResults::Rel(RelResult { width, values })
},
}
}
pub fn into_scalar(self) -> Result<Option<Binding>> {
self.results.into_scalar()
}
pub fn into_coll(self) -> Result<Vec<Binding>> {
self.results.into_coll()
}
/// Mentat tuple results can be expressed as multiple different data structures. Some
/// structures are generic (vectors) and some are easier for pattern matching (fixed length
/// tuples).
///
/// This is the moral equivalent of `collect` (and `BindingTuple` of `FromIterator`), but
/// specialized to tuples of expected length.
pub fn into_tuple<B>(self) -> Result<Option<B>> where B: BindingTuple {
let expected = self.spec.expected_column_count();
self.results.into_tuple().and_then(|vec| B::from_binding_vec(expected, vec))
}
pub fn into_rel(self) -> Result<RelResult<Binding>> {
self.results.into_rel()
}
}
impl QueryResults {
pub fn len(&self) -> usize {
use QueryResults::*;
match self {
&Scalar(ref o) => if o.is_some() { 1 } else { 0 },
&Tuple(ref o) => if o.is_some() { 1 } else { 0 },
&Coll(ref v) => v.len(),
&Rel(ref r) => r.row_count(),
}
}
pub fn is_empty(&self) -> bool {
use QueryResults::*;
match self {
&Scalar(ref o) => o.is_none(),
&Tuple(ref o) => o.is_none(),
&Coll(ref v) => v.is_empty(),
&Rel(ref r) => r.is_empty(),
}
}
pub fn into_scalar(self) -> Result<Option<Binding>> {
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match self {
QueryResults::Scalar(o) => Ok(o),
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QueryResults::Coll(_) => bail!(ProjectorError::UnexpectedResultsType("coll", "scalar")),
QueryResults::Tuple(_) => bail!(ProjectorError::UnexpectedResultsType("tuple", "scalar")),
QueryResults::Rel(_) => bail!(ProjectorError::UnexpectedResultsType("rel", "scalar")),
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}
}
pub fn into_coll(self) -> Result<Vec<Binding>> {
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match self {
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QueryResults::Scalar(_) => bail!(ProjectorError::UnexpectedResultsType("scalar", "coll")),
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QueryResults::Coll(c) => Ok(c),
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QueryResults::Tuple(_) => bail!(ProjectorError::UnexpectedResultsType("tuple", "coll")),
QueryResults::Rel(_) => bail!(ProjectorError::UnexpectedResultsType("rel", "coll")),
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}
}
pub fn into_tuple(self) -> Result<Option<Vec<Binding>>> {
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match self {
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QueryResults::Scalar(_) => bail!(ProjectorError::UnexpectedResultsType("scalar", "tuple")),
QueryResults::Coll(_) => bail!(ProjectorError::UnexpectedResultsType("coll", "tuple")),
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QueryResults::Tuple(t) => Ok(t),
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QueryResults::Rel(_) => bail!(ProjectorError::UnexpectedResultsType("rel", "tuple")),
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}
}
pub fn into_rel(self) -> Result<RelResult<Binding>> {
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match self {
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QueryResults::Scalar(_) => bail!(ProjectorError::UnexpectedResultsType("scalar", "rel")),
QueryResults::Coll(_) => bail!(ProjectorError::UnexpectedResultsType("coll", "rel")),
QueryResults::Tuple(_) => bail!(ProjectorError::UnexpectedResultsType("tuple", "rel")),
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QueryResults::Rel(r) => Ok(r),
}
}
}
type Index = usize; // See rusqlite::RowIndex.
enum TypedIndex {
Known(Index, ValueTypeTag),
Unknown(Index, Index),
}
impl TypedIndex {
/// Look up this index and type(index) pair in the provided row.
/// This function will panic if:
///
/// - This is an `Unknown` and the retrieved type tag isn't an i32.
/// - If the retrieved value can't be coerced to a rusqlite `Value`.
/// - Either index is out of bounds.
///
/// Because we construct our SQL projection list, the tag that stored the data, and this
/// consumer, a panic here implies that we have a bad bug — we put data of a very wrong type in
/// a row, and thus can't coerce to Value, we're retrieving from the wrong place, or our
/// generated SQL is junk.
///
/// This function will return a runtime error if the type tag is unknown, or the value is
/// otherwise not convertible by the DB layer.
fn lookup<'a>(&self, row: &Row<'a>) -> Result<Binding> {
use TypedIndex::*;
match self {
&Known(value_index, value_type) => {
let v: rusqlite::types::Value = row.get(value_index).unwrap();
TypedValue::from_sql_value_pair(v, value_type)
.map(|v| v.into())
.map_err(|e| e.into())
},
&Unknown(value_index, type_index) => {
let v: rusqlite::types::Value = row.get(value_index).unwrap();
let value_type_tag: i32 = row.get(type_index).unwrap();
TypedValue::from_sql_value_pair(v, value_type_tag)
.map(|v| v.into())
.map_err(|e| e.into())
},
}
}
}
/// Combines the things you need to turn a query into SQL and turn its results into
/// `QueryResults`: SQL-related projection information (`DISTINCT`, columns, etc.) and
/// a Datalog projector that turns SQL into structures.
pub struct CombinedProjection {
/// A SQL projection, mapping columns mentioned in the body of the query to columns in the
/// output.
pub sql_projection: Projection,
/// If a query contains aggregates, we need to generate a nested subquery: an inner query
/// that returns our distinct variable bindings (and any `:with` vars), and an outer query
/// that applies aggregation. That's so we can put `DISTINCT` in the inner query and apply
/// aggregation afterwards -- `SELECT DISTINCT count(foo)` counts _then_ uniques, and we need
/// the opposite to implement Datalog distinct semantics.
/// If this is the case, `sql_projection` will be the outer query's projection list, and
/// `pre_aggregate_projection` will be the inner.
/// If the query doesn't use aggregation, this field will be `None`.
pub pre_aggregate_projection: Option<Projection>,
/// A Datalog projection. This consumes rows of the appropriate shape (as defined by
/// the SQL projection) to yield one of the four kinds of Datalog query result.
pub datalog_projector: Box<Projector>,
/// True if this query requires the SQL query to include DISTINCT.
pub distinct: bool,
// A list of column names to use as a GROUP BY clause.
pub group_by_cols: Vec<GroupBy>,
}
impl CombinedProjection {
fn flip_distinct_for_limit(mut self, limit: &Limit) -> Self {
if *limit == Limit::Fixed(1) {
self.distinct = false;
}
self
}
}
trait IsPull {
fn is_pull(&self) -> bool;
}
impl IsPull for Element {
fn is_pull(&self) -> bool {
match self {
&Element::Pull(_) => true,
_ => false,
}
}
}
/// Compute a suitable SQL projection for an algebrized query.
/// This takes into account a number of things:
/// - The variable list in the find spec.
/// - The presence of any aggregate operations in the find spec. TODO: for now we only handle
/// simple variables
/// - The bindings established by the topmost CC.
/// - The types known at algebrizing time.
/// - The types extracted from the store for unknown attributes.
pub fn query_projection(schema: &Schema, query: &AlgebraicQuery) -> Result<Either<ConstantProjector, CombinedProjection>> {
use self::FindSpec::*;
let spec = query.find_spec.clone();
if query.is_fully_unit_bound() {
// Do a few gyrations to produce empty results of the right kind for the query.
let variables: BTreeSet<Variable> = spec.columns()
.map(|e| match e {
&Element::Variable(ref var) |
&Element::Corresponding(ref var) => var.clone(),
// Pull expressions can never be fully bound.
// TODO: but the interior can be, in which case we
// can handle this and simply project.
&Element::Pull(_) => {
unreachable!();
},
&Element::Aggregate(ref _agg) => {
// TODO: static computation of aggregates, then
// implement the condition in `is_fully_bound`.
unreachable!();
},
})
.collect();
// TODO: error handling
let results = QueryOutput::from_constants(&spec, query.cc.value_bindings(&variables));
let f = Box::new(move || { results.clone() });
Ok(Either::Left(ConstantProjector::new(spec, f)))
} else if query.is_known_empty() {
// Do a few gyrations to produce empty results of the right kind for the query.
let empty = QueryOutput::empty_factory(&spec);
Ok(Either::Left(ConstantProjector::new(spec, empty)))
} else {
match *query.find_spec {
FindColl(ref element) => {
let elements = project_elements(1, iter::once(element), query)?;
if element.is_pull() {
CollTwoStagePullProjector::combine(spec, elements)
} else {
CollProjector::combine(spec, elements)
}.map(|p| p.flip_distinct_for_limit(&query.limit))
},
FindScalar(ref element) => {
let elements = project_elements(1, iter::once(element), query)?;
if element.is_pull() {
ScalarTwoStagePullProjector::combine(schema, spec, elements)
} else {
ScalarProjector::combine(spec, elements)
}
},
FindRel(ref elements) => {
let is_pull = elements.iter().any(|e| e.is_pull());
let column_count = query.find_spec.expected_column_count();
let elements = project_elements(column_count, elements, query)?;
if is_pull {
RelTwoStagePullProjector::combine(spec, column_count, elements)
} else {
RelProjector::combine(spec, column_count, elements)
}.map(|p| p.flip_distinct_for_limit(&query.limit))
},
FindTuple(ref elements) => {
let is_pull = elements.iter().any(|e| e.is_pull());
let column_count = query.find_spec.expected_column_count();
let elements = project_elements(column_count, elements, query)?;
if is_pull {
TupleTwoStagePullProjector::combine(spec, column_count, elements)
} else {
TupleProjector::combine(spec, column_count, elements)
}
},
}.map(Either::Right)
}
}
#[test]
fn test_into_tuple() {
let query_output = QueryOutput {
spec: Rc::new(FindSpec::FindTuple(vec![Element::Variable(Variable::from_valid_name("?x")),
Element::Variable(Variable::from_valid_name("?y"))])),
results: QueryResults::Tuple(Some(vec![Binding::Scalar(TypedValue::Long(0)),
Binding::Scalar(TypedValue::Long(2))])),
};
assert_eq!(query_output.clone().into_tuple().expect("into_tuple"),
Some((Binding::Scalar(TypedValue::Long(0)),
Binding::Scalar(TypedValue::Long(2)))));
match query_output.clone().into_tuple() {
Err(ProjectorError::UnexpectedResultsTupleLength(expected, got)) => {
assert_eq!((expected, got), (3, 2));
},
// This forces the result type.
Ok(Some((_, _, _))) | _ => panic!("expected error"),
}
let query_output = QueryOutput {
spec: Rc::new(FindSpec::FindTuple(vec![Element::Variable(Variable::from_valid_name("?x")),
Element::Variable(Variable::from_valid_name("?y"))])),
results: QueryResults::Tuple(None),
};
match query_output.clone().into_tuple() {
Ok(None) => {},
// This forces the result type.
Ok(Some((_, _))) | _ => panic!("expected error"),
}
match query_output.clone().into_tuple() {
Err(ProjectorError::UnexpectedResultsTupleLength(expected, got)) => {
assert_eq!((expected, got), (3, 2));
},
// This forces the result type.
Ok(Some((_, _, _))) | _ => panic!("expected error"),
}
}