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Commit5e6d8d2

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Allow parallel workers to execute subplans.
This doesn't do anything to make Param nodes anything other thanparallel-restricted, so this only helps with uncorrelated subplans,and it's not necessarily very cheap because each worker will run thesubplan separately (just as a Hash Join will build a separate copy ofthe hash table in each participating process), but it's a first steptoward supporting cases that are more likely to help in practice, andis occasionally useful on its own.Amit Kapila, reviewed and tested by Rafia Sabih, Dilip Kumar, andme.Discussion:http://postgr.es/m/CAA4eK1+e8Z45D2n+rnDMDYsVEb5iW7jqaCH_tvPMYau=1Rru9w@mail.gmail.com
1 parent8da9a22 commit5e6d8d2

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10 files changed

+61
-14
lines changed

10 files changed

+61
-14
lines changed

‎src/backend/executor/execParallel.c‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -156,7 +156,7 @@ ExecSerializePlan(Plan *plan, EState *estate)
156156
pstmt->planTree=plan;
157157
pstmt->rtable=estate->es_range_table;
158158
pstmt->resultRelations=NIL;
159-
pstmt->subplans=NIL;
159+
pstmt->subplans=estate->es_plannedstmt->subplans;
160160
pstmt->rewindPlanIDs=NULL;
161161
pstmt->rowMarks=NIL;
162162
pstmt->relationOids=NIL;

‎src/backend/nodes/copyfuncs.c‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1495,6 +1495,7 @@ _copySubPlan(const SubPlan *from)
14951495
COPY_SCALAR_FIELD(firstColCollation);
14961496
COPY_SCALAR_FIELD(useHashTable);
14971497
COPY_SCALAR_FIELD(unknownEqFalse);
1498+
COPY_SCALAR_FIELD(parallel_safe);
14981499
COPY_NODE_FIELD(setParam);
14991500
COPY_NODE_FIELD(parParam);
15001501
COPY_NODE_FIELD(args);

‎src/backend/nodes/equalfuncs.c‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -423,6 +423,7 @@ _equalSubPlan(const SubPlan *a, const SubPlan *b)
423423
COMPARE_SCALAR_FIELD(firstColCollation);
424424
COMPARE_SCALAR_FIELD(useHashTable);
425425
COMPARE_SCALAR_FIELD(unknownEqFalse);
426+
COMPARE_SCALAR_FIELD(parallel_safe);
426427
COMPARE_NODE_FIELD(setParam);
427428
COMPARE_NODE_FIELD(parParam);
428429
COMPARE_NODE_FIELD(args);

‎src/backend/nodes/outfuncs.c‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1226,6 +1226,7 @@ _outSubPlan(StringInfo str, const SubPlan *node)
12261226
WRITE_OID_FIELD(firstColCollation);
12271227
WRITE_BOOL_FIELD(useHashTable);
12281228
WRITE_BOOL_FIELD(unknownEqFalse);
1229+
WRITE_BOOL_FIELD(parallel_safe);
12291230
WRITE_NODE_FIELD(setParam);
12301231
WRITE_NODE_FIELD(parParam);
12311232
WRITE_NODE_FIELD(args);

‎src/backend/nodes/readfuncs.c‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -2233,6 +2233,7 @@ _readSubPlan(void)
22332233
READ_OID_FIELD(firstColCollation);
22342234
READ_BOOL_FIELD(useHashTable);
22352235
READ_BOOL_FIELD(unknownEqFalse);
2236+
READ_BOOL_FIELD(parallel_safe);
22362237
READ_NODE_FIELD(setParam);
22372238
READ_NODE_FIELD(parParam);
22382239
READ_NODE_FIELD(args);

‎src/backend/optimizer/plan/subselect.c‎

Lines changed: 13 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -58,7 +58,7 @@ static Node *build_subplan(PlannerInfo *root, Plan *plan, PlannerInfo *subroot,
5858
List*plan_params,
5959
SubLinkTypesubLinkType,intsubLinkId,
6060
Node*testexpr,booladjust_testexpr,
61-
boolunknownEqFalse);
61+
boolunknownEqFalse,boolparallel_safe);
6262
staticList*generate_subquery_params(PlannerInfo*root,List*tlist,
6363
List**paramIds);
6464
staticList*generate_subquery_vars(PlannerInfo*root,List*tlist,
@@ -551,7 +551,8 @@ make_subplan(PlannerInfo *root, Query *orig_subquery,
551551
/* And convert to SubPlan or InitPlan format. */
552552
result=build_subplan(root,plan,subroot,plan_params,
553553
subLinkType,subLinkId,
554-
testexpr, true,isTopQual);
554+
testexpr, true,isTopQual,
555+
best_path->parallel_safe);
555556

556557
/*
557558
* If it's a correlated EXISTS with an unimportant targetlist, we might be
@@ -604,7 +605,8 @@ make_subplan(PlannerInfo *root, Query *orig_subquery,
604605
plan_params,
605606
ANY_SUBLINK,0,
606607
newtestexpr,
607-
false, true);
608+
false, true,
609+
best_path->parallel_safe);
608610
/* Check we got what we expected */
609611
Assert(IsA(hashplan,SubPlan));
610612
Assert(hashplan->parParam==NIL);
@@ -634,7 +636,7 @@ build_subplan(PlannerInfo *root, Plan *plan, PlannerInfo *subroot,
634636
List*plan_params,
635637
SubLinkTypesubLinkType,intsubLinkId,
636638
Node*testexpr,booladjust_testexpr,
637-
boolunknownEqFalse)
639+
boolunknownEqFalse,boolparallel_safe)
638640
{
639641
Node*result;
640642
SubPlan*splan;
@@ -653,6 +655,7 @@ build_subplan(PlannerInfo *root, Plan *plan, PlannerInfo *subroot,
653655
&splan->firstColCollation);
654656
splan->useHashTable= false;
655657
splan->unknownEqFalse=unknownEqFalse;
658+
splan->parallel_safe=parallel_safe;
656659
splan->setParam=NIL;
657660
splan->parParam=NIL;
658661
splan->args=NIL;
@@ -1213,6 +1216,12 @@ SS_process_ctes(PlannerInfo *root)
12131216
&splan->firstColCollation);
12141217
splan->useHashTable= false;
12151218
splan->unknownEqFalse= false;
1219+
1220+
/*
1221+
* CTE scans are not considered for parallelism (cf
1222+
* set_rel_consider_parallel).
1223+
*/
1224+
splan->parallel_safe= false;
12161225
splan->setParam=NIL;
12171226
splan->parParam=NIL;
12181227
splan->args=NIL;

‎src/backend/optimizer/util/clauses.c‎

Lines changed: 7 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -1162,21 +1162,19 @@ max_parallel_hazard_walker(Node *node, max_parallel_hazard_context *context)
11621162
}
11631163

11641164
/*
1165-
* Since we don't have the ability to push subplans down to workers at
1166-
* present, we treat subplan references as parallel-restricted. We need
1167-
* not worry about examining their contents; if they are unsafe, we would
1168-
* have found that out while examining the whole tree before reduction of
1169-
* sublinks to subplans. (Really we should not see SubLink during a
1170-
* max_interesting == restricted scan, but if we do, return true.)
1165+
* Really we should not see SubLink during a max_interesting == restricted
1166+
* scan, but if we do, return true.
11711167
*/
1172-
elseif (IsA(node,SubLink)||
1173-
IsA(node,SubPlan)||
1174-
IsA(node,AlternativeSubPlan))
1168+
elseif (IsA(node,SubLink))
11751169
{
11761170
if (max_parallel_hazard_test(PROPARALLEL_RESTRICTED,context))
11771171
return true;
11781172
}
11791173

1174+
/* We can push the subplans only if they are parallel-safe. */
1175+
elseif (IsA(node,SubPlan))
1176+
return !((SubPlan*)node)->parallel_safe;
1177+
11801178
/*
11811179
* We can't pass Params to workers at the moment either, so they are also
11821180
* parallel-restricted.

‎src/include/nodes/primnodes.h‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -677,6 +677,7 @@ typedef struct SubPlan
677677
boolunknownEqFalse;/* TRUE if it's okay to return FALSE when the
678678
* spec result is UNKNOWN; this allows much
679679
* simpler handling of null values */
680+
boolparallel_safe;/* OK to use as part of parallel plan? */
680681
/* Information for passing params into and out of the subselect: */
681682
/* setParam and parParam are lists of integers (param IDs) */
682683
List*setParam;/* initplan subqueries have to set these

‎src/test/regress/expected/select_parallel.out‎

Lines changed: 26 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -99,6 +99,32 @@ explain (costs off)
9999
-> Index Only Scan using tenk1_unique1 on tenk1
100100
(3 rows)
101101

102+
-- test parallel plans for queries containing un-correlated subplans.
103+
alter table tenk2 set (parallel_workers = 0);
104+
explain (costs off)
105+
select count(*) from tenk1 where (two, four) not in
106+
(select hundred, thousand from tenk2 where thousand > 100);
107+
QUERY PLAN
108+
------------------------------------------------------
109+
Finalize Aggregate
110+
-> Gather
111+
Workers Planned: 4
112+
-> Partial Aggregate
113+
-> Parallel Seq Scan on tenk1
114+
Filter: (NOT (hashed SubPlan 1))
115+
SubPlan 1
116+
-> Seq Scan on tenk2
117+
Filter: (thousand > 100)
118+
(9 rows)
119+
120+
select count(*) from tenk1 where (two, four) not in
121+
(select hundred, thousand from tenk2 where thousand > 100);
122+
count
123+
-------
124+
10000
125+
(1 row)
126+
127+
alter table tenk2 reset (parallel_workers);
102128
set force_parallel_mode=1;
103129
explain (costs off)
104130
select stringu1::int2 from tenk1 where unique1 = 1;

‎src/test/regress/sql/select_parallel.sql‎

Lines changed: 9 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -39,6 +39,15 @@ explain (costs off)
3939
selectsum(parallel_restricted(unique1))from tenk1
4040
group by(parallel_restricted(unique1));
4141

42+
-- test parallel plans for queries containing un-correlated subplans.
43+
altertable tenk2set (parallel_workers=0);
44+
explain (costs off)
45+
selectcount(*)from tenk1where (two, four) notin
46+
(select hundred, thousandfrom tenk2where thousand>100);
47+
selectcount(*)from tenk1where (two, four) notin
48+
(select hundred, thousandfrom tenk2where thousand>100);
49+
altertable tenk2 reset (parallel_workers);
50+
4251
set force_parallel_mode=1;
4352

4453
explain (costs off)

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