diff options
Diffstat (limited to 'src/backend/optimizer/path/equivclass.c')
| -rw-r--r-- | src/backend/optimizer/path/equivclass.c | 27 |
1 files changed, 15 insertions, 12 deletions
diff --git a/src/backend/optimizer/path/equivclass.c b/src/backend/optimizer/path/equivclass.c index 6e87fba2aa3..6f1abbe47d6 100644 --- a/src/backend/optimizer/path/equivclass.c +++ b/src/backend/optimizer/path/equivclass.c @@ -961,18 +961,21 @@ find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel) } /* - * Find an equivalence class member expression that can be used to build - * a sort node using the provided relation; return NULL if no candidate. + * relation_can_be_sorted_early + * Can this relation be sorted on this EC before the final output step? * * To succeed, we must find an EC member that prepare_sort_from_pathkeys knows * how to sort on, given the rel's reltarget as input. There are also a few * additional constraints based on the fact that the desired sort will be done - * within the scan/join part of the plan. Also, non-parallel-safe expressions - * are ignored if 'require_parallel_safe'. + * "early", within the scan/join part of the plan. Also, non-parallel-safe + * expressions are ignored if 'require_parallel_safe'. + * + * At some point we might want to return the identified EquivalenceMember, + * but for now, callers only want to know if there is one. */ -Expr * -find_em_expr_usable_for_sorting_rel(PlannerInfo *root, EquivalenceClass *ec, - RelOptInfo *rel, bool require_parallel_safe) +bool +relation_can_be_sorted_early(PlannerInfo *root, RelOptInfo *rel, + EquivalenceClass *ec, bool require_parallel_safe) { PathTarget *target = rel->reltarget; EquivalenceMember *em; @@ -982,7 +985,7 @@ find_em_expr_usable_for_sorting_rel(PlannerInfo *root, EquivalenceClass *ec, * Reject volatile ECs immediately; such sorts must always be postponed. */ if (ec->ec_has_volatile) - return NULL; + return false; /* * Try to find an EM directly matching some reltarget member. @@ -1012,7 +1015,7 @@ find_em_expr_usable_for_sorting_rel(PlannerInfo *root, EquivalenceClass *ec, !is_parallel_safe(root, (Node *) em->em_expr)) continue; - return em->em_expr; + return true; } /* @@ -1021,7 +1024,7 @@ find_em_expr_usable_for_sorting_rel(PlannerInfo *root, EquivalenceClass *ec, em = find_computable_ec_member(root, ec, target->exprs, rel->relids, require_parallel_safe); if (!em) - return NULL; + return false; /* * Reject expressions involving set-returning functions, as those can't be @@ -1030,9 +1033,9 @@ find_em_expr_usable_for_sorting_rel(PlannerInfo *root, EquivalenceClass *ec, * belong to multi-member ECs.) */ if (IS_SRF_CALL((Node *) em->em_expr)) - return NULL; + return false; - return em->em_expr; + return true; } /* |