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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2012-04-09 11:58:24 -0400 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2012-04-09 11:58:40 -0400 |
| commit | 0e20abdb47e3499353ac4fd1b2d21e82ec6b1461 (patch) | |
| tree | 64c0b3e3cb3f071ac0481c28f37a213df41071b7 /src/backend/utils/adt | |
| parent | 88e071533fba70747aaf8d9b32fb927b7157ad16 (diff) | |
| download | postgresql-0e20abdb47e3499353ac4fd1b2d21e82ec6b1461.tar.gz postgresql-0e20abdb47e3499353ac4fd1b2d21e82ec6b1461.zip | |
Fix an Assert that turns out to be reachable after all.
estimate_num_groups() gets unhappy with
create table empty();
select * from empty except select * from empty e2;
I can't see any actual use-case for such a query (and the table is illegal
per SQL spec), but it seems like a good idea that it not cause an assert
failure.
Diffstat (limited to 'src/backend/utils/adt')
| -rw-r--r-- | src/backend/utils/adt/selfuncs.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c index 55e42025c6b..d700b86b934 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -3068,8 +3068,13 @@ estimate_num_groups(PlannerInfo *root, List *groupExprs, double input_rows) double numdistinct; ListCell *l; - /* We should not be called unless query has GROUP BY (or DISTINCT) */ - Assert(groupExprs != NIL); + /* + * If no grouping columns, there's exactly one group. (This can't happen + * for normal cases with GROUP BY or DISTINCT, but it is possible for + * corner cases with set operations.) + */ + if (groupExprs == NIL) + return 1.0; /* * Count groups derived from boolean grouping expressions. For other |