database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-09-03 15:22:11 +03:00
Code Activity

Flush Memoize cache when non-key parameters change, take 2

Browse Source 
It's possible that a subplan below a Memoize node contains a parameter
from above the Memoize node.  If this parameter changes then cache entries
may become out-dated due to the new parameter value.

Previously Memoize was mistakenly not aware of this.  We fix this here by
flushing the cache whenever a parameter that's not part of the cache
key changes.

Bug: #17213
Reported by: Elvis Pranskevichus
Author: David Rowley
Discussion: https://postgr.es/m/17213-988ed34b225a2862@postgresql.org
Backpatch-through: 14, where Memoize was added
This commit is contained in:
David Rowley
2021-11-24 23:29:56 +13:00
parent 0e681fa458
commit c2dc7b9e15
12 changed files with 145 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

39
src/test/regress/expected/memoize.out
View File

@@ -196,6 +196,45 @@ SELECT * FROM strtest s1 INNER JOIN strtest s2 ON s1.t >= s2.t;', false);
(8 rows)
DROP TABLE strtest;
-- Exercise Memoize code that flushes the cache when a parameter changes which
-- is not part of the cache key.
-- Ensure we get a Memoize plan
EXPLAIN (COSTS OFF)
SELECT unique1 FROM tenk1 t0
WHERE unique1 < 3
AND EXISTS (
SELECT 1 FROM tenk1 t1
INNER JOIN tenk1 t2 ON t1.unique1 = t2.hundred
WHERE t0.ten = t1.twenty AND t0.two <> t2.four OFFSET 0);
QUERY PLAN
----------------------------------------------------------------
Index Scan using tenk1_unique1 on tenk1 t0
Index Cond: (unique1 < 3)
Filter: (SubPlan 1)
SubPlan 1
-> Nested Loop
-> Index Scan using tenk1_hundred on tenk1 t2
Filter: (t0.two <> four)
-> Memoize
Cache Key: t2.hundred
Cache Mode: logical
-> Index Scan using tenk1_unique1 on tenk1 t1
Index Cond: (unique1 = t2.hundred)
Filter: (t0.ten = twenty)
(13 rows)
-- Ensure the above query returns the correct result
SELECT unique1 FROM tenk1 t0
WHERE unique1 < 3
AND EXISTS (
SELECT 1 FROM tenk1 t1
INNER JOIN tenk1 t2 ON t1.unique1 = t2.hundred
WHERE t0.ten = t1.twenty AND t0.two <> t2.four OFFSET 0);
unique1
---------
2
(1 row)
RESET enable_seqscan;
RESET enable_mergejoin;
RESET work_mem;

20
src/test/regress/sql/memoize.sql
View File

@@ -103,6 +103,26 @@ SELECT * FROM strtest s1 INNER JOIN strtest s2 ON s1.t >= s2.t;', false);
DROP TABLE strtest;
-- Exercise Memoize code that flushes the cache when a parameter changes which
-- is not part of the cache key.
-- Ensure we get a Memoize plan
EXPLAIN (COSTS OFF)
SELECT unique1 FROM tenk1 t0
WHERE unique1 < 3
AND EXISTS (
SELECT 1 FROM tenk1 t1
INNER JOIN tenk1 t2 ON t1.unique1 = t2.hundred
WHERE t0.ten = t1.twenty AND t0.two <> t2.four OFFSET 0);
-- Ensure the above query returns the correct result
SELECT unique1 FROM tenk1 t0
WHERE unique1 < 3
AND EXISTS (
SELECT 1 FROM tenk1 t1
INNER JOIN tenk1 t2 ON t1.unique1 = t2.hundred
WHERE t0.ten = t1.twenty AND t0.two <> t2.four OFFSET 0);
RESET enable_seqscan;
RESET enable_mergejoin;
RESET work_mem;