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Commit44ae64c

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Push target list evaluation through Gather Merge.
We already do this for Gather, but it got overlooked for Gather Merge.Amit Kapila, with review and minor revisions by Rushabh Lathiaand by me.Discussion:http://postgr.es/m/CAA4eK1KUC5Uyu7qaifxrjpHxbSeoQh3yzwN3bThnJsmJcZ-qtA@mail.gmail.com
1 parente64861c commit44ae64c

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4 files changed

+69
-17
lines changed

4 files changed

+69
-17
lines changed

‎src/backend/optimizer/plan/planner.c‎

Lines changed: 2 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -5060,7 +5060,8 @@ create_ordered_paths(PlannerInfo *root,
50605060
path= (Path*)
50615061
create_gather_merge_path(root,ordered_rel,
50625062
path,
5063-
target,root->sort_pathkeys,NULL,
5063+
path->pathtarget,
5064+
root->sort_pathkeys,NULL,
50645065
&total_groups);
50655066

50665067
/* Add projection step if needed */

‎src/backend/optimizer/util/pathnode.c‎

Lines changed: 29 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -2368,9 +2368,9 @@ create_projection_path(PlannerInfo *root,
23682368
* knows that the given path isn't referenced elsewhere and so can be modified
23692369
* in-place.
23702370
*
2371-
* If the input path is a GatherPath, we try to push the new target down to
2372-
* its input as well; this is a yet more invasive modification of the input
2373-
* path, which create_projection_path() can't do.
2371+
* If the input path is a GatherPath or GatherMergePath, we try to push the
2372+
*new target down toits input as well; this is a yet more invasive
2373+
*modification of the inputpath, which create_projection_path() can't do.
23742374
*
23752375
* Note that we mustn't change the source path's parent link; so when it is
23762376
* add_path'd to "rel" things will be a bit inconsistent. So far that has
@@ -2407,31 +2407,44 @@ apply_projection_to_path(PlannerInfo *root,
24072407
(target->cost.per_tuple-oldcost.per_tuple)*path->rows;
24082408

24092409
/*
2410-
* If the path happens to be a Gather path, we'd like to arrange for the
2411-
* subpath to return the required target list so that workers can help
2412-
* project. But if there is something that is not parallel-safe in the
2413-
* target expressions, then we can't.
2410+
* If the path happens to be a Gatheror GatherMergepath, we'd like to
2411+
*arrange for thesubpath to return the required target list so that
2412+
*workers can helpproject. But if there is something that is not
2413+
*parallel-safe in thetarget expressions, then we can't.
24142414
*/
2415-
if (IsA(path,GatherPath)&&
2415+
if ((IsA(path,GatherPath)||IsA(path,GatherMergePath))&&
24162416
is_parallel_safe(root, (Node*)target->exprs))
24172417
{
2418-
GatherPath*gpath= (GatherPath*)path;
2419-
24202418
/*
24212419
* We always use create_projection_path here, even if the subpath is
24222420
* projection-capable, so as to avoid modifying the subpath in place.
24232421
* It seems unlikely at present that there could be any other
24242422
* references to the subpath, but better safe than sorry.
24252423
*
2426-
* Note that we don't change theGatherPath's cost estimates; it might
2424+
* Note that we don't change theparallel path's cost estimates; it might
24272425
* be appropriate to do so, to reflect the fact that the bulk of the
24282426
* target evaluation will happen in workers.
24292427
*/
2430-
gpath->subpath= (Path*)
2431-
create_projection_path(root,
2432-
gpath->subpath->parent,
2433-
gpath->subpath,
2434-
target);
2428+
if (IsA(path,GatherPath))
2429+
{
2430+
GatherPath*gpath= (GatherPath*)path;
2431+
2432+
gpath->subpath= (Path*)
2433+
create_projection_path(root,
2434+
gpath->subpath->parent,
2435+
gpath->subpath,
2436+
target);
2437+
}
2438+
else
2439+
{
2440+
GatherMergePath*gmpath= (GatherMergePath*)path;
2441+
2442+
gmpath->subpath= (Path*)
2443+
create_projection_path(root,
2444+
gmpath->subpath->parent,
2445+
gmpath->subpath,
2446+
target);
2447+
}
24352448
}
24362449
elseif (path->parallel_safe&&
24372450
!is_parallel_safe(root, (Node*)target->exprs))

‎src/test/regress/expected/select_parallel.out‎

Lines changed: 25 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -375,6 +375,31 @@ select count(*) from tenk1 group by twenty;
375375
500
376376
(20 rows)
377377

378+
--test expressions in targetlist are pushed down for gather merge
379+
create or replace function simple_func(var1 integer) returns integer
380+
as $$
381+
begin
382+
return var1 + 10;
383+
end;
384+
$$ language plpgsql PARALLEL SAFE;
385+
explain (costs off, verbose)
386+
select ten, simple_func(ten) from tenk1 where ten < 100 order by ten;
387+
QUERY PLAN
388+
-----------------------------------------------------
389+
Gather Merge
390+
Output: ten, (simple_func(ten))
391+
Workers Planned: 4
392+
-> Result
393+
Output: ten, simple_func(ten)
394+
-> Sort
395+
Output: ten
396+
Sort Key: tenk1.ten
397+
-> Parallel Seq Scan on public.tenk1
398+
Output: ten
399+
Filter: (tenk1.ten < 100)
400+
(11 rows)
401+
402+
drop function simple_func(integer);
378403
--test rescan behavior of gather merge
379404
set enable_material = false;
380405
explain (costs off)

‎src/test/regress/sql/select_parallel.sql‎

Lines changed: 13 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -144,6 +144,19 @@ explain (costs off)
144144

145145
selectcount(*)from tenk1group by twenty;
146146

147+
--test expressions in targetlist are pushed down for gather merge
148+
create or replacefunctionsimple_func(var1integer) returnsinteger
149+
as $$
150+
begin
151+
return var1+10;
152+
end;
153+
$$ language plpgsql PARALLEL SAFE;
154+
155+
explain (costs off, verbose)
156+
select ten, simple_func(ten)from tenk1where ten<100order by ten;
157+
158+
dropfunction simple_func(integer);
159+
147160
--test rescan behavior of gather merge
148161
set enable_material= false;
149162

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