diff options
| 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 11:59:11 -0400 |
| commit | 8555586707dbf5f731f015691a87cc0ab53efcca (patch) | |
| tree | cc7a0814f9aba13d9b18feaae53d11208ebb0120 /src | |
| parent | cd8b1c6d48d664fe2e5575f40707ed247cee4aa0 (diff) | |
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')
| -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 165fd29ae16..7fe5e74527c 100644 --- a/src/backend/utils/adt/selfuncs.c +++ b/src/backend/utils/adt/selfuncs.c @@ -2983,8 +2983,13 @@ 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 |