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Commit05c8482

Browse files
author
Amit Kapila
committed
Enable parallel SELECT for "INSERT INTO ... SELECT ...".
Parallel SELECT can't be utilized for INSERT in the following cases:- INSERT statement uses the ON CONFLICT DO UPDATE clause- Target table has a parallel-unsafe: trigger, index expression or predicate, column default expression or check constraint- Target table has a parallel-unsafe domain constraint on any column- Target table is a partitioned table with a parallel-unsafe partition key expression or support functionThe planner is updated to perform additional parallel-safety checks forthe cases listed above, for determining whether it is safe to run INSERTin parallel-mode with an underlying parallel SELECT. The planner willconsider using parallel SELECT for "INSERT INTO ... SELECT ...", providednothing unsafe is found from the additional parallel-safety checks, orfrom the existing parallel-safety checks for SELECT.While checking parallel-safety, we need to check it for all the partitionson the table which can be costly especially when we decide not to use aparallel plan. So, in a separate patch, we will introduce a GUC and or areloption to enable/disable parallelism for Insert statements.Prior to entering parallel-mode for the execution of INSERT with parallelSELECT, a TransactionId is acquired and assigned to the currenttransaction state. This is necessary to prevent the INSERT from attemptingto assign the TransactionId whilst in parallel-mode, which is not allowed.This approach has a disadvantage in that if the underlying SELECT does notreturn any rows, then the TransactionId is not used, however thatshouldn't happen in practice in many cases.Author: Greg Nancarrow, Amit Langote, Amit KapilaReviewed-by: Amit Langote, Hou Zhijie, Takayuki Tsunakawa, Antonin Houska, Bharath Rupireddy, Dilip Kumar, Vignesh C, Zhihong Yu, Amit KapilaTested-by: Tang, HaiyingDiscussion:https://postgr.es/m/CAJcOf-cXnB5cnMKqWEp2E2z7Mvcd04iLVmV=qpFJrR3AcrTS3g@mail.gmail.comDiscussion:https://postgr.es/m/CAJcOf-fAdj=nDKMsRhQzndm-O13NY4dL6xGcEvdX5Xvbbi0V7g@mail.gmail.com
1 parent0ba7110 commit05c8482

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17 files changed

+1531
-21
lines changed

17 files changed

+1531
-21
lines changed

‎doc/src/sgml/parallel.sgml‎

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -146,7 +146,9 @@ EXPLAIN SELECT * FROM pgbench_accounts WHERE filler LIKE '%x%';
146146
a CTE, no parallel plans for that query will be generated. As an
147147
exception, the commands <literal>CREATE TABLE ... AS</literal>, <literal>SELECT
148148
INTO</literal>, and <literal>CREATE MATERIALIZED VIEW</literal> which create a new
149-
table and populate it can use a parallel plan.
149+
table and populate it can use a parallel plan. Another exception is the command
150+
<literal>INSERT INTO ... SELECT ...</literal> which can use a parallel plan for
151+
the underlying <literal>SELECT</literal> part of the query.
150152
</para>
151153
</listitem>
152154

‎src/backend/access/transam/xact.c‎

Lines changed: 26 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1014,6 +1014,32 @@ IsInParallelMode(void)
10141014
returnCurrentTransactionState->parallelModeLevel!=0;
10151015
}
10161016

1017+
/*
1018+
*PrepareParallelModePlanExec
1019+
*
1020+
* Prepare for entering parallel mode plan execution, based on command-type.
1021+
*/
1022+
void
1023+
PrepareParallelModePlanExec(CmdTypecommandType)
1024+
{
1025+
if (IsModifySupportedInParallelMode(commandType))
1026+
{
1027+
Assert(!IsInParallelMode());
1028+
1029+
/*
1030+
* Prepare for entering parallel mode by assigning a TransactionId.
1031+
* Failure to do this now would result in heap_insert() subsequently
1032+
* attempting to assign a TransactionId whilst in parallel-mode, which
1033+
* is not allowed.
1034+
*
1035+
* This approach has a disadvantage in that if the underlying SELECT
1036+
* does not return any rows, then the TransactionId is not used,
1037+
* however that shouldn't happen in practice in many cases.
1038+
*/
1039+
(void)GetCurrentTransactionId();
1040+
}
1041+
}
1042+
10171043
/*
10181044
*CommandCounterIncrement
10191045
*/

‎src/backend/executor/execMain.c‎

Lines changed: 3 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1512,7 +1512,10 @@ ExecutePlan(EState *estate,
15121512

15131513
estate->es_use_parallel_mode=use_parallel_mode;
15141514
if (use_parallel_mode)
1515+
{
1516+
PrepareParallelModePlanExec(estate->es_plannedstmt->commandType);
15151517
EnterParallelMode();
1518+
}
15161519

15171520
/*
15181521
* Loop until we've processed the proper number of tuples from the plan.

‎src/backend/nodes/copyfuncs.c‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -96,6 +96,7 @@ _copyPlannedStmt(const PlannedStmt *from)
9696
COPY_BITMAPSET_FIELD(rewindPlanIDs);
9797
COPY_NODE_FIELD(rowMarks);
9898
COPY_NODE_FIELD(relationOids);
99+
COPY_NODE_FIELD(partitionOids);
99100
COPY_NODE_FIELD(invalItems);
100101
COPY_NODE_FIELD(paramExecTypes);
101102
COPY_NODE_FIELD(utilityStmt);

‎src/backend/nodes/outfuncs.c‎

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -314,6 +314,7 @@ _outPlannedStmt(StringInfo str, const PlannedStmt *node)
314314
WRITE_BITMAPSET_FIELD(rewindPlanIDs);
315315
WRITE_NODE_FIELD(rowMarks);
316316
WRITE_NODE_FIELD(relationOids);
317+
WRITE_NODE_FIELD(partitionOids);
317318
WRITE_NODE_FIELD(invalItems);
318319
WRITE_NODE_FIELD(paramExecTypes);
319320
WRITE_NODE_FIELD(utilityStmt);
@@ -2221,6 +2222,7 @@ _outPlannerGlobal(StringInfo str, const PlannerGlobal *node)
22212222
WRITE_NODE_FIELD(resultRelations);
22222223
WRITE_NODE_FIELD(appendRelations);
22232224
WRITE_NODE_FIELD(relationOids);
2225+
WRITE_NODE_FIELD(partitionOids);
22242226
WRITE_NODE_FIELD(invalItems);
22252227
WRITE_NODE_FIELD(paramExecTypes);
22262228
WRITE_UINT_FIELD(lastPHId);

‎src/backend/nodes/readfuncs.c‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1590,6 +1590,7 @@ _readPlannedStmt(void)
15901590
READ_BITMAPSET_FIELD(rewindPlanIDs);
15911591
READ_NODE_FIELD(rowMarks);
15921592
READ_NODE_FIELD(relationOids);
1593+
READ_NODE_FIELD(partitionOids);
15931594
READ_NODE_FIELD(invalItems);
15941595
READ_NODE_FIELD(paramExecTypes);
15951596
READ_NODE_FIELD(utilityStmt);

‎src/backend/optimizer/plan/planner.c‎

Lines changed: 26 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -305,6 +305,7 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
305305
glob->resultRelations=NIL;
306306
glob->appendRelations=NIL;
307307
glob->relationOids=NIL;
308+
glob->partitionOids=NIL;
308309
glob->invalItems=NIL;
309310
glob->paramExecTypes=NIL;
310311
glob->lastPHId=0;
@@ -316,16 +317,16 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
316317
/*
317318
* Assess whether it's feasible to use parallel mode for this query. We
318319
* can't do this in a standalone backend, or if the command will try to
319-
* modify any data, or if this is a cursor operation, or if GUCs are set
320-
* to values that don't permit parallelism, or if parallel-unsafe
321-
* functions are present in the query tree.
320+
* modify any data (except for Insert), or if this is a cursor operation,
321+
*or if GUCs are setto values that don't permit parallelism, or if
322+
*parallel-unsafefunctions are present in the query tree.
322323
*
323-
* (Note that we do allow CREATE TABLE AS,SELECT INTO, and CREATE
324-
* MATERIALIZED VIEW to use parallel plans, but as of now, only the leader
325-
* backend writes into a completely new table. In the future, we can
326-
* extend it to allow workers to write into the table. However, to allow
327-
* parallel updates and deletes, we have to solve other problems,
328-
* especially around combo CIDs.)
324+
* (Note that we do allow CREATE TABLE AS,INSERT INTO...SELECT, SELECT
325+
*INTO, and CREATEMATERIALIZED VIEW to use parallel plans. However, as
326+
*of now, only the leaderbackend writes into a completely new table.In
327+
*the future, we canextend it to allow workers to write into the table.
328+
*However, to allowparallel updates and deletes, we have to solve other
329+
*problems,especially around combo CIDs.)
329330
*
330331
* For now, we don't try to use parallel mode if we're running inside a
331332
* parallel worker. We might eventually be able to relax this
@@ -334,13 +335,14 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
334335
*/
335336
if ((cursorOptions&CURSOR_OPT_PARALLEL_OK)!=0&&
336337
IsUnderPostmaster&&
337-
parse->commandType==CMD_SELECT&&
338+
(parse->commandType==CMD_SELECT||
339+
is_parallel_allowed_for_modify(parse))&&
338340
!parse->hasModifyingCTE&&
339341
max_parallel_workers_per_gather>0&&
340342
!IsParallelWorker())
341343
{
342344
/* all the cheap tests pass, so scan the query tree */
343-
glob->maxParallelHazard=max_parallel_hazard(parse);
345+
glob->maxParallelHazard=max_parallel_hazard(parse,glob);
344346
glob->parallelModeOK= (glob->maxParallelHazard!=PROPARALLEL_UNSAFE);
345347
}
346348
else
@@ -521,6 +523,19 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
521523
result->rewindPlanIDs=glob->rewindPlanIDs;
522524
result->rowMarks=glob->finalrowmarks;
523525
result->relationOids=glob->relationOids;
526+
527+
/*
528+
* Register the Oids of parallel-safety-checked partitions as plan
529+
* dependencies. This is only really needed in the case of a parallel plan
530+
* so that if parallel-unsafe properties are subsequently defined on the
531+
* partitions, the cached parallel plan will be invalidated, and a
532+
* non-parallel plan will be generated.
533+
*
534+
* We also use this list to acquire locks on partitions before executing
535+
* cached plan. See AcquireExecutorLocks().
536+
*/
537+
if (glob->partitionOids!=NIL&&glob->parallelModeNeeded)
538+
result->partitionOids=glob->partitionOids;
524539
result->invalItems=glob->invalItems;
525540
result->paramExecTypes=glob->paramExecTypes;
526541
/* utilityStmt should be null, but we might as well copy it */

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