From 8fafdc4852b8f2164286e6863219eb6b4d267639 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Thu, 29 Aug 2024 16:25:23 -0400 Subject: [PATCH v1 1/2] Remove one memoize test case added by commit 069d0ff02. This test case turns out to depend on the assumption that a non-Var subquery output that's underneath an outer join will always get wrapped in a PlaceHolderVar. But that behavior causes performance regressions in some cases compared to what happened before v16. The next commit will avoid inserting a PHV in the same cases where pre-v16 did, and that causes get_memoized_path to not detect that a memoize plan could be used. Commit this separately, in hopes that we can restore the test after making get_memoized_path smarter. (It's failing to find memoize plans in adjacent cases where no PHV was ever inserted, so there is definitely room for improvement there.) Discussion: https://postgr.es/m/CAG1ps1xvnTZceKK24OUfMKLPvDP2vjT-d+F2AOCWbw_v3KeEgg@mail.gmail.com --- src/test/regress/expected/memoize.out | 30 --------------------------- src/test/regress/sql/memoize.sql | 11 ---------- 2 files changed, 41 deletions(-) diff --git a/src/test/regress/expected/memoize.out b/src/test/regress/expected/memoize.out index df2ca5ba4e..9ee09fe2f5 100644 --- a/src/test/regress/expected/memoize.out +++ b/src/test/regress/expected/memoize.out @@ -160,36 +160,6 @@ WHERE s.c1 = s.c2 AND t1.unique1 < 1000; 1000 | 9.5000000000000000 (1 row) --- Try with LATERAL references within PlaceHolderVars -SELECT explain_memoize(' -SELECT COUNT(*), AVG(t1.twenty) FROM tenk1 t1 LEFT JOIN -LATERAL (SELECT t1.two+t2.two AS c1, t2.unique1 AS c2 FROM tenk1 t2) s ON TRUE -WHERE s.c1 = s.c2 AND t1.unique1 < 1000;', false); - explain_memoize --------------------------------------------------------------------------------------- - Aggregate (actual rows=1 loops=N) - -> Nested Loop (actual rows=1000 loops=N) - -> Seq Scan on tenk1 t1 (actual rows=1000 loops=N) - Filter: (unique1 < 1000) - Rows Removed by Filter: 9000 - -> Memoize (actual rows=1 loops=N) - Cache Key: t1.two - Cache Mode: binary - Hits: 998 Misses: 2 Evictions: Zero Overflows: 0 Memory Usage: NkB - -> Seq Scan on tenk1 t2 (actual rows=1 loops=N) - Filter: ((t1.two + two) = unique1) - Rows Removed by Filter: 9999 -(12 rows) - --- And check we get the expected results. -SELECT COUNT(*), AVG(t1.twenty) FROM tenk1 t1 LEFT JOIN -LATERAL (SELECT t1.two+t2.two AS c1, t2.unique1 AS c2 FROM tenk1 t2) s ON TRUE -WHERE s.c1 = s.c2 AND t1.unique1 < 1000; - count | avg --------+-------------------- - 1000 | 9.0000000000000000 -(1 row) - -- Ensure we do not omit the cache keys from PlaceHolderVars SELECT explain_memoize(' SELECT COUNT(*), AVG(t1.twenty) FROM tenk1 t1 LEFT JOIN diff --git a/src/test/regress/sql/memoize.sql b/src/test/regress/sql/memoize.sql index 059bec5f4f..2eaeb1477a 100644 --- a/src/test/regress/sql/memoize.sql +++ b/src/test/regress/sql/memoize.sql @@ -85,17 +85,6 @@ SELECT COUNT(*), AVG(t1.twenty) FROM tenk1 t1 LEFT JOIN LATERAL (SELECT t1.two+1 AS c1, t2.unique1 AS c2 FROM tenk1 t2) s ON TRUE WHERE s.c1 = s.c2 AND t1.unique1 < 1000; --- Try with LATERAL references within PlaceHolderVars -SELECT explain_memoize(' -SELECT COUNT(*), AVG(t1.twenty) FROM tenk1 t1 LEFT JOIN -LATERAL (SELECT t1.two+t2.two AS c1, t2.unique1 AS c2 FROM tenk1 t2) s ON TRUE -WHERE s.c1 = s.c2 AND t1.unique1 < 1000;', false); - --- And check we get the expected results. -SELECT COUNT(*), AVG(t1.twenty) FROM tenk1 t1 LEFT JOIN -LATERAL (SELECT t1.two+t2.two AS c1, t2.unique1 AS c2 FROM tenk1 t2) s ON TRUE -WHERE s.c1 = s.c2 AND t1.unique1 < 1000; - -- Ensure we do not omit the cache keys from PlaceHolderVars SELECT explain_memoize(' SELECT COUNT(*), AVG(t1.twenty) FROM tenk1 t1 LEFT JOIN -- 2.43.5