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Commit7645376

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Rename find_em_expr_usable_for_sorting_rel.
I didn't particularly like this function name, as it fails toexpress what's going on. Also, returning the sort expressionalone isn't too helpful --- typically, a caller would alsoneed some other fields of the EquivalenceMember. But thesole caller really only needs a bool result, so let's makeit "bool relation_can_be_sorted_early()".Discussion:https://postgr.es/m/91f3ec99-85a4-fa55-ea74-33f85a5c651f@swarm64.com
1 parent3753982 commit7645376

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3 files changed

+28
-27
lines changed

3 files changed

+28
-27
lines changed

‎src/backend/optimizer/path/allpaths.c

Lines changed: 10 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -2697,20 +2697,19 @@ get_useful_pathkeys_for_relation(PlannerInfo *root, RelOptInfo *rel,
26972697
EquivalenceClass*pathkey_ec=pathkey->pk_eclass;
26982698

26992699
/*
2700-
* We can only build a sort for pathkeyswhich containan EC
2701-
*member in the current relation's target, so ignore any suffix
2702-
*of the list as soon as we find a pathkey without an EC member
2703-
*in the relation.
2700+
* We can only build a sort for pathkeysthat containa
2701+
*safe-to-compute-early EC member computable from the current
2702+
*relation's reltarget, so ignore the remainder of the list as
2703+
*soon as we find a pathkey without such a member.
27042704
*
2705-
* By still returning the prefix of the pathkeys list that does
2706-
* meet criteria of EC membership in the current relation, we
2707-
* enable not just an incremental sort on the entirety of
2708-
* query_pathkeys but also incremental sort below a JOIN.
2705+
* It's still worthwhile to return any prefix of the pathkeys list
2706+
* that meets this requirement, as we may be able to do an
2707+
* incremental sort.
27092708
*
2710-
* If requested, ensure the expression is parallelsafe too.
2709+
* If requested, ensure thesortexpression is parallel-safe too.
27112710
*/
2712-
if (!find_em_expr_usable_for_sorting_rel(root,pathkey_ec,rel,
2713-
require_parallel_safe))
2711+
if (!relation_can_be_sorted_early(root,rel,pathkey_ec,
2712+
require_parallel_safe))
27142713
break;
27152714

27162715
npathkeys++;

‎src/backend/optimizer/path/equivclass.c

Lines changed: 15 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -961,18 +961,21 @@ find_em_expr_for_rel(EquivalenceClass *ec, RelOptInfo *rel)
961961
}
962962

963963
/*
964-
*Find an equivalence class member expression that can be used to build
965-
* a sort node using the provided relation; return NULL if no candidate.
964+
*relation_can_be_sorted_early
965+
*Can this relation be sorted on this EC before the final output step?
966966
*
967967
* To succeed, we must find an EC member that prepare_sort_from_pathkeys knows
968968
* how to sort on, given the rel's reltarget as input. There are also a few
969969
* additional constraints based on the fact that the desired sort will be done
970-
* within the scan/join part of the plan. Also, non-parallel-safe expressions
971-
* are ignored if 'require_parallel_safe'.
970+
* "early", within the scan/join part of the plan. Also, non-parallel-safe
971+
* expressions are ignored if 'require_parallel_safe'.
972+
*
973+
* At some point we might want to return the identified EquivalenceMember,
974+
* but for now, callers only want to know if there is one.
972975
*/
973-
Expr*
974-
find_em_expr_usable_for_sorting_rel(PlannerInfo*root,EquivalenceClass*ec,
975-
RelOptInfo*rel,boolrequire_parallel_safe)
976+
bool
977+
relation_can_be_sorted_early(PlannerInfo*root,RelOptInfo*rel,
978+
EquivalenceClass*ec,boolrequire_parallel_safe)
976979
{
977980
PathTarget*target=rel->reltarget;
978981
EquivalenceMember*em;
@@ -982,7 +985,7 @@ find_em_expr_usable_for_sorting_rel(PlannerInfo *root, EquivalenceClass *ec,
982985
* Reject volatile ECs immediately; such sorts must always be postponed.
983986
*/
984987
if (ec->ec_has_volatile)
985-
returnNULL;
988+
returnfalse;
986989

987990
/*
988991
* 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,
10121015
!is_parallel_safe(root, (Node*)em->em_expr))
10131016
continue;
10141017

1015-
returnem->em_expr;
1018+
returntrue;
10161019
}
10171020

10181021
/*
@@ -1021,7 +1024,7 @@ find_em_expr_usable_for_sorting_rel(PlannerInfo *root, EquivalenceClass *ec,
10211024
em=find_computable_ec_member(root,ec,target->exprs,rel->relids,
10221025
require_parallel_safe);
10231026
if (!em)
1024-
returnNULL;
1027+
returnfalse;
10251028

10261029
/*
10271030
* 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,
10301033
* belong to multi-member ECs.)
10311034
*/
10321035
if (IS_SRF_CALL((Node*)em->em_expr))
1033-
returnNULL;
1036+
returnfalse;
10341037

1035-
returnem->em_expr;
1038+
returntrue;
10361039
}
10371040

10381041
/*

‎src/include/optimizer/paths.h

Lines changed: 3 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -144,10 +144,9 @@ extern EquivalenceMember *find_computable_ec_member(PlannerInfo *root,
144144
Relidsrelids,
145145
boolrequire_parallel_safe);
146146
externExpr*find_em_expr_for_rel(EquivalenceClass*ec,RelOptInfo*rel);
147-
externExpr*find_em_expr_usable_for_sorting_rel(PlannerInfo*root,
148-
EquivalenceClass*ec,
149-
RelOptInfo*rel,
150-
boolrequire_parallel_safe);
147+
externboolrelation_can_be_sorted_early(PlannerInfo*root,RelOptInfo*rel,
148+
EquivalenceClass*ec,
149+
boolrequire_parallel_safe);
151150
externvoidgenerate_base_implied_equalities(PlannerInfo*root);
152151
externList*generate_join_implied_equalities(PlannerInfo*root,
153152
Relidsjoin_relids,

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