diff options
Diffstat (limited to 'src/include/nodes/pathnodes.h')
| -rw-r--r-- | src/include/nodes/pathnodes.h | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h index 78489398294..2ba297c1172 100644 --- a/src/include/nodes/pathnodes.h +++ b/src/include/nodes/pathnodes.h @@ -426,7 +426,11 @@ struct PlannerInfo * items to be proven redundant, implying that there is only one group * containing all the query's rows. Hence, if you want to check whether * GROUP BY was specified, test for nonempty parse->groupClause, not for - * nonempty processed_groupClause. + * nonempty processed_groupClause. Optimizer chooses specific order of + * group-by clauses during the upper paths generation process, attempting + * to use different strategies to minimize number of sorts or engage + * incremental sort. See preprocess_groupclause() and + * get_useful_group_keys_orderings() for details. * * Currently, when grouping sets are specified we do not attempt to * optimize the groupClause, so that processed_groupClause will be |