diff options
| author | David Rowley <drowley@postgresql.org> | 2022-09-20 09:13:49 +1200 |
|---|---|---|
| committer | David Rowley <drowley@postgresql.org> | 2022-09-20 09:13:49 +1200 |
| commit | 78a9af1a27641ad983354bbaaaa4b7c00ea390f6 (patch) | |
| tree | ea64ab1971e049ec3e02f8cdb42a39ddb170b328 /src/backend/optimizer/plan/planner.c | |
| parent | 66fa8ff637982b51257d80626dd00dccf3ad9fa6 (diff) | |
| download | postgresql-78a9af1a27641ad983354bbaaaa4b7c00ea390f6.tar.gz postgresql-78a9af1a27641ad983354bbaaaa4b7c00ea390f6.zip | |
Fix out-dated comment in preprocess_groupclause()
The comment claimed we don't consider other orders of the GROUP BY clause,
but this is no longer true as of db0d67db2.
Discussion: https://postgr.es/m/CAApHDvq65=9Ro+hLX1i9ugWEiNDvHrBibAO7ARcTnf38_JE+UQ@mail.gmail.com
Backpatch-through: 15, where db0d67db2 was introduced.
Diffstat (limited to 'src/backend/optimizer/plan/planner.c')
| -rw-r--r-- | src/backend/optimizer/plan/planner.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c index 079bd0bfdfd..c0bdc77d390 100644 --- a/src/backend/optimizer/plan/planner.c +++ b/src/backend/optimizer/plan/planner.c @@ -2758,8 +2758,9 @@ remove_useless_groupby_columns(PlannerInfo *root) * * In principle it might be interesting to consider other orderings of the * GROUP BY elements, which could match the sort ordering of other - * possible plans (eg an indexscan) and thereby reduce cost. We don't - * bother with that, though. Hashed grouping will frequently win anyway. + * possible plans (eg an indexscan) and thereby reduce cost. However, we + * don't yet have sufficient information to do that here, so that's left until + * later in planning. See get_useful_group_keys_orderings(). * * Note: we need no comparable processing of the distinctClause because * the parser already enforced that that matches ORDER BY. |