diff options
| -rw-r--r-- | src/backend/optimizer/path/equivclass.c | 8 | ||||
| -rw-r--r-- | src/backend/optimizer/plan/createplan.c | 3 |
2 files changed, 8 insertions, 3 deletions
diff --git a/src/backend/optimizer/path/equivclass.c b/src/backend/optimizer/path/equivclass.c index 1e151dd510c..b93c11155c7 100644 --- a/src/backend/optimizer/path/equivclass.c +++ b/src/backend/optimizer/path/equivclass.c @@ -795,9 +795,11 @@ find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel) } /* - * Find an equivalence class member expression that can be safely used by a - * sort node on top of the provided relation. The rules here must match those - * applied in prepare_sort_from_pathkeys. + * Find an equivalence class member expression that can be safely used to build + * a sort node using the provided relation. The rules are a subset of those + * applied in prepare_sort_from_pathkeys since that function deals with sorts + * that must be delayed until the last stages of query execution, while here + * we only care about proactive sorts. */ Expr * find_em_expr_usable_for_sorting_rel(PlannerInfo *root, EquivalenceClass *ec, diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c index b3ab169f78c..84f2d186d95 100644 --- a/src/backend/optimizer/plan/createplan.c +++ b/src/backend/optimizer/plan/createplan.c @@ -5844,6 +5844,9 @@ make_incrementalsort(Plan *lefttree, int numCols, int nPresortedCols, * * Returns the node which is to be the input to the Sort (either lefttree, * or a Result stacked atop lefttree). + * + * Note: Restrictions on what expressions are safely sortable may also need to + * be added to find_em_expr_usable_for_sorting_rel. */ static Plan * prepare_sort_from_pathkeys(Plan *lefttree, List *pathkeys, |