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Commit69f75bf

Browse files
author
Etsuro Fujita
committed
postgres_fdw: Fix assertion in estimate_path_cost_size().
Commit08d2d58 added this assertion assuming that the retrieved_rowsestimate for a foreign relation is set to at least one row inestimate_path_cost_size(), but the assumption isn't correct because ifthe relation is a foreign table with tuples=0, the estimate would be setto 0 in there when using local stats, and if the query's WHERE clausehas a NULL condition, the estimate could be set to 0 in there when usingremote estimates. (Note: even in the latter case the assertion could bereachable when costing foreign final paths.) Repair.Per bug #17713 from Robins Tharakan. This patch was already applied tov13 or later; apply it to v12 as well where the aforementioned commitwas added. Thanks to Richard Guo for investigation.Discussion:http://postgr.es/m/17713-92cce66de7e81c04%40postgresql.orgDiscussion:http://postgr.es/m/CAEP4nAza%2B0fTCLkgkKYux3JDo3tUBTQORehP%2BaCxSNURpSFpHw%40mail.gmail.com
1 parent1cca4a7 commit69f75bf

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3 files changed

+31
-1
lines changed

3 files changed

+31
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‎contrib/postgres_fdw/expected/postgres_fdw.out

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Original file line numberDiff line numberDiff line change
@@ -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
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RESET enable_hashjoin;
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RESET enable_nestloop;
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-- Test executing assertion in estimate_path_cost_size() that makes sure that
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-- retrieved_rows for foreign rel re-used to cost pre-sorted foreign paths is
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-- a sensible value even when the rel has tuples=0
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CREATE TABLE loct_empty (c1 int NOT NULL, c2 text);
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CREATE FOREIGN TABLE ft_empty (c1 int NOT NULL, c2 text)
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SERVER loopback OPTIONS (table_name 'loct_empty');
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INSERT INTO loct_empty
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SELECT id, 'AAA' || to_char(id, 'FM000') FROM generate_series(1, 100) id;
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DELETE FROM loct_empty;
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ANALYZE ft_empty;
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EXPLAIN (VERBOSE, COSTS OFF) SELECT * FROM ft_empty ORDER BY c1;
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QUERY PLAN
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-------------------------------------------------------------------------------
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Foreign Scan on public.ft_empty
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Output: c1, c2
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Remote SQL: SELECT c1, c2 FROM public.loct_empty ORDER BY c1 ASC NULLS LAST
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(3 rows)
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-- ===================================================================
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-- WHERE with remotely-executable conditions
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-- ===================================================================

‎contrib/postgres_fdw/postgres_fdw.c

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -2749,7 +2749,7 @@ estimate_path_cost_size(PlannerInfo *root,
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*/
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if (fpinfo->rel_startup_cost >=0&&fpinfo->rel_total_cost >=0)
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{
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Assert(fpinfo->retrieved_rows >=1);
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Assert(fpinfo->retrieved_rows >=0);
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rows=fpinfo->rows;
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retrieved_rows=fpinfo->retrieved_rows;

‎contrib/postgres_fdw/sql/postgres_fdw.sql

Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -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
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RESET enable_hashjoin;
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RESET enable_nestloop;
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-- Test executing assertion in estimate_path_cost_size() that makes sure that
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-- retrieved_rows for foreign rel re-used to cost pre-sorted foreign paths is
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-- a sensible value even when the rel has tuples=0
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CREATETABLEloct_empty (c1intNOT NULL, c2text);
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CREATE FOREIGN TABLE ft_empty (c1intNOT NULL, c2text)
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SERVER loopback OPTIONS (table_name'loct_empty');
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INSERT INTO loct_empty
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SELECT id,'AAA'|| to_char(id,'FM000')FROM generate_series(1,100) id;
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DELETEFROM loct_empty;
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ANALYZE ft_empty;
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EXPLAIN (VERBOSE, COSTS OFF)SELECT*FROM ft_emptyORDER BY c1;
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-- ===================================================================
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-- WHERE with remotely-executable conditions
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-- ===================================================================

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