From 53248c5840ca3f159f9dc5ec941c8309ed2c10b5 Mon Sep 17 00:00:00 2001
From: Grisha Kruglov <gkruglov@mozilla.com>
Date: Mon, 5 Feb 2018 19:46:03 -0500
Subject: [PATCH] broken peekable

---
 tests/tolstoy.rs            |  2 ++
 tolstoy/src/tx_processor.rs | 64 ++++++++++++++++++++++++-------------
 2 files changed, 44 insertions(+), 22 deletions(-)

diff --git a/tests/tolstoy.rs b/tests/tolstoy.rs
index 744973f6..d515a3ae 100644
--- a/tests/tolstoy.rs
+++ b/tests/tolstoy.rs
@@ -115,6 +115,8 @@ fn test_reader() {
     let mut receiver = TestingReceiver::new();
     Processor::process(&c, &mut receiver).expect("processor");
 
+    println!("{:#?}", receiver);
+
     assert_eq!(2, receiver.txes.keys().count());
     assert_tx_datoms_count(&receiver, 1, 4);
 
diff --git a/tolstoy/src/tx_processor.rs b/tolstoy/src/tx_processor.rs
index 89e4293a..05545634 100644
--- a/tolstoy/src/tx_processor.rs
+++ b/tolstoy/src/tx_processor.rs
@@ -7,6 +7,9 @@
 // // 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 core;
+
+use self::core::iter::Peekable;
 
 use rusqlite;
 
@@ -29,6 +32,7 @@ pub struct TxPart {
     pub e: Entid,
     pub a: Entid,
     pub v: TypedValue,
+    pub tx: Entid,
     pub added: bool,
 }
 
@@ -45,28 +49,25 @@ pub trait TxReceiver {
 
 pub struct Processor {}
 
-struct RawDatom {
-    e: Entid,
-    a: Entid,
-    v: TypedValue, // composite of 'v' and 'value_type_tag'
-    tx: Entid,
-    added: bool,
-}
+type DemRows<'s> = Peekable<rusqlite::AndThenRows<'s, Result<TxPart>>>;
 
 pub struct DatomsIterator<'conn> {
     at_first: bool,
     at_last: bool,
-    first: &'conn RawDatom,
-    rows: &'conn mut Iterator<Item=Result<RawDatom>>,
+    first: &'conn TxPart,
+    rows: DemRows<'conn>,
 }
 
 impl<'conn> DatomsIterator<'conn> {
-    fn new(first: &'conn RawDatom, rows: &'conn mut Iterator<Item=Result<RawDatom>>) -> DatomsIterator<'conn> {
+    fn new<I>(first: &'conn TxPart, rows: &'conn mut DemRows<'conn>) -> DatomsIterator<'conn>
+    where
+        I: Iterator<Item=Result<TxPart>>
+    {
         DatomsIterator {
             at_first: true,
             at_last: false,
             first: first,
-            rows: rows
+            rows: Box::new(rows),
         }
     }
 }
@@ -81,14 +82,30 @@ impl<'conn> Iterator for DatomsIterator<'conn> {
 
         if self.at_first {
             self.at_first = false;
-            return Some(Ok(TxPart {
-                e: self.first.e,
-                a: self.first.a,
-                v: self.first.v.clone(),
-                added: self.first.added,
-            }));
+            return Some(Ok(self.first.clone()));
         }
 
+        // Look ahead to see if we're about to cross into
+        // the next partition.
+        {
+            let next_option = self.rows.peek();
+            match next_option {
+                Some(next_result) => {
+                    match *next_result {
+                        Ok(ref next) => {
+                            if next.tx != self.first.tx {
+                                self.at_last = true;
+                                return None;
+                            }
+                        },
+                        _ => ()
+                    }
+                },
+                _ => ()
+            }
+        }
+        
+        // We're in the correct partition.
         if let Some(row) = self.rows.next() {
             let datom = match row {
                 Ok(r) => r,
@@ -106,6 +123,7 @@ impl<'conn> Iterator for DatomsIterator<'conn> {
                 e: datom.e,
                 a: datom.a,
                 v: datom.v.clone(),
+                tx: datom.tx,
                 added: datom.added,
             }));
         } else {
@@ -121,8 +139,8 @@ impl Processor {
             "SELECT e, a, v, tx, added, value_type_tag FROM transactions ORDER BY tx"
         )?;
 
-        let mut rows = stmt.query_and_then(&[], |row| -> Result<RawDatom> {
-            Ok(RawDatom {
+        let mut rows = stmt.query_and_then(&[], |row| -> Result<TxPart> {
+            Ok(TxPart {
                 e: row.get(0),
                 a: row.get(1),
                 v: TypedValue::from_sql_value_pair(row.get(2), row.get(5))?,
@@ -133,9 +151,11 @@ impl Processor {
 
         let mut current_tx = None;
 
-        while let Some(row) = rows.next() {
+        let mut peekable = rows.peekable();
+        while let Some(row) = peekable.next() {
             let datom = row?;
             
+            // if current_tx == Some(row.tx)
             match current_tx {
                 Some(tx) => {
                     if tx == datom.tx {
@@ -144,7 +164,7 @@ impl Processor {
                         current_tx = Some(datom.tx);
                         receiver.tx(
                             datom.tx,
-                            &mut DatomsIterator::new(&datom, &mut rows)
+                            &mut DatomsIterator::new(&datom, &mut peekable)
                         )?;
                         continue;
                     }
@@ -153,7 +173,7 @@ impl Processor {
                     current_tx = Some(datom.tx);
                     receiver.tx(
                         datom.tx,
-                        &mut DatomsIterator::new(&datom, &mut rows)
+                        &mut DatomsIterator::new(&datom, &mut peekable)
                     )?;
                 }
             }