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postgres_fdw: Fix assertion in estimate_path_cost_size().

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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
This commit is contained in:
Etsuro Fujita
2022-12-15 21:15:00 +09:00
parent 1cca4a75ff
commit 69f75bf825
3 changed files with 31 additions and 1 deletions
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2
contrib/postgres_fdw/postgres_fdw.c
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@ -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;