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| author | Etsuro Fujita <efujita@postgresql.org> | 2022-12-15 21:15:00 +0900 |
|---|---|---|
| committer | Etsuro Fujita <efujita@postgresql.org> | 2022-12-15 21:15:00 +0900 |
| commit | 69f75bf825f83dc506e73cf88f0adde541c39004 (patch) | |
| tree | 156d2045b6a49fe323afa2e39558bdc7dcf94146 | |
| parent | 1cca4a75ffb82c7e0497e6195b7fb3ed44dc430e (diff) | |
| download | postgresql-69f75bf825f83dc506e73cf88f0adde541c39004.tar.gz postgresql-69f75bf825f83dc506e73cf88f0adde541c39004.zip | |
postgres_fdw: Fix assertion in estimate_path_cost_size().
Commit 08d2d58a2 added this assertion assuming that the retrieved_rows
estimate for a foreign relation is set to at least one row in
estimate_path_cost_size(), but the assumption isn't correct because if
the relation is a foreign table with tuples=0, the estimate would be set
to 0 in there when using local stats, and if the query's WHERE clause
has a NULL condition, the estimate could be set to 0 in there when using
remote estimates. (Note: even in the latter case the assertion could be
reachable when costing foreign final paths.) Repair.
Per bug #17713 from Robins Tharakan. This patch was already applied to
v13 or later; apply it to v12 as well where the aforementioned commit
was added. Thanks to Richard Guo for investigation.
Discussion: http://postgr.es/m/17713-92cce66de7e81c04%40postgresql.org
Discussion: http://postgr.es/m/CAEP4nAza%2B0fTCLkgkKYux3JDo3tUBTQORehP%2BaCxSNURpSFpHw%40mail.gmail.com
| -rw-r--r-- | contrib/postgres_fdw/expected/postgres_fdw.out | 18 | ||||
| -rw-r--r-- | contrib/postgres_fdw/postgres_fdw.c | 2 | ||||
| -rw-r--r-- | contrib/postgres_fdw/sql/postgres_fdw.sql | 12 |
3 files changed, 31 insertions, 1 deletions
diff --git a/contrib/postgres_fdw/expected/postgres_fdw.out b/contrib/postgres_fdw/expected/postgres_fdw.out index 92cff268ca8..e3cc20ff4bf 100644 --- a/contrib/postgres_fdw/expected/postgres_fdw.out +++ b/contrib/postgres_fdw/expected/postgres_fdw.out @@ -590,6 +590,24 @@ SELECT t1."C 1", t2.c1, t3.c1 FROM "S 1"."T 1" t1 full join ft1 t2 full join ft2 RESET enable_hashjoin; RESET enable_nestloop; +-- Test executing assertion in estimate_path_cost_size() that makes sure that +-- retrieved_rows for foreign rel re-used to cost pre-sorted foreign paths is +-- a sensible value even when the rel has tuples=0 +CREATE TABLE loct_empty (c1 int NOT NULL, c2 text); +CREATE FOREIGN TABLE ft_empty (c1 int NOT NULL, c2 text) + SERVER loopback OPTIONS (table_name 'loct_empty'); +INSERT INTO loct_empty + SELECT id, 'AAA' || to_char(id, 'FM000') FROM generate_series(1, 100) id; +DELETE FROM loct_empty; +ANALYZE ft_empty; +EXPLAIN (VERBOSE, COSTS OFF) SELECT * FROM ft_empty ORDER BY c1; + QUERY PLAN +------------------------------------------------------------------------------- + Foreign Scan on public.ft_empty + Output: c1, c2 + Remote SQL: SELECT c1, c2 FROM public.loct_empty ORDER BY c1 ASC NULLS LAST +(3 rows) + -- =================================================================== -- WHERE with remotely-executable conditions -- =================================================================== diff --git a/contrib/postgres_fdw/postgres_fdw.c b/contrib/postgres_fdw/postgres_fdw.c index a4d0377f31f..7aa6d7c549c 100644 --- a/contrib/postgres_fdw/postgres_fdw.c +++ b/contrib/postgres_fdw/postgres_fdw.c @@ -2749,7 +2749,7 @@ estimate_path_cost_size(PlannerInfo *root, */ if (fpinfo->rel_startup_cost >= 0 && fpinfo->rel_total_cost >= 0) { - Assert(fpinfo->retrieved_rows >= 1); + Assert(fpinfo->retrieved_rows >= 0); rows = fpinfo->rows; retrieved_rows = fpinfo->retrieved_rows; diff --git a/contrib/postgres_fdw/sql/postgres_fdw.sql b/contrib/postgres_fdw/sql/postgres_fdw.sql index 3118ac5468b..6cc8b251ccc 100644 --- a/contrib/postgres_fdw/sql/postgres_fdw.sql +++ b/contrib/postgres_fdw/sql/postgres_fdw.sql @@ -285,6 +285,18 @@ SELECT t1."C 1", t2.c1, t3.c1 FROM "S 1"."T 1" t1 full join ft1 t2 full join ft2 RESET enable_hashjoin; RESET enable_nestloop; +-- Test executing assertion in estimate_path_cost_size() that makes sure that +-- retrieved_rows for foreign rel re-used to cost pre-sorted foreign paths is +-- a sensible value even when the rel has tuples=0 +CREATE TABLE loct_empty (c1 int NOT NULL, c2 text); +CREATE FOREIGN TABLE ft_empty (c1 int NOT NULL, c2 text) + SERVER loopback OPTIONS (table_name 'loct_empty'); +INSERT INTO loct_empty + SELECT id, 'AAA' || to_char(id, 'FM000') FROM generate_series(1, 100) id; +DELETE FROM loct_empty; +ANALYZE ft_empty; +EXPLAIN (VERBOSE, COSTS OFF) SELECT * FROM ft_empty ORDER BY c1; + -- =================================================================== -- WHERE with remotely-executable conditions -- =================================================================== |