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Enable parallel SELECT for "INSERT INTO ... SELECT ...".

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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 function

The planner is updated to perform additional parallel-safety checks for
the cases listed above, for determining whether it is safe to run INSERT
in parallel-mode with an underlying parallel SELECT. The planner will
consider using parallel SELECT for "INSERT INTO ... SELECT ...", provided
nothing unsafe is found from the additional parallel-safety checks, or
from the existing parallel-safety checks for SELECT.

While checking parallel-safety, we need to check it for all the partitions
on the table which can be costly especially when we decide not to use a
parallel plan. So, in a separate patch, we will introduce a GUC and or a
reloption to enable/disable parallelism for Insert statements.

Prior to entering parallel-mode for the execution of INSERT with parallel
SELECT, a TransactionId is acquired and assigned to the current
transaction state. This is necessary to prevent the INSERT from attempting
to assign the TransactionId whilst in parallel-mode, which is not allowed.
This approach has a disadvantage in that if the underlying SELECT does not
return any rows, then the TransactionId is not used, however that
shouldn't happen in practice in many cases.

Author: Greg Nancarrow, Amit Langote, Amit Kapila
Reviewed-by: Amit Langote, Hou Zhijie, Takayuki Tsunakawa, Antonin Houska, Bharath Rupireddy, Dilip Kumar, Vignesh C, Zhihong Yu, Amit Kapila
Tested-by: Tang, Haiying
Discussion: https://postgr.es/m/CAJcOf-cXnB5cnMKqWEp2E2z7Mvcd04iLVmV=qpFJrR3AcrTS3g@mail.gmail.com
Discussion: https://postgr.es/m/CAJcOf-fAdj=nDKMsRhQzndm-O13NY4dL6xGcEvdX5Xvbbi0V7g@mail.gmail.com
This commit is contained in:
Amit Kapila
2021-03-10 07:38:58 +05:30
parent 0ba71107ef
commit 05c8482f7f
17 changed files with 1531 additions and 21 deletions
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33
src/backend/utils/cache/plancache.c vendored
View File

@ -1735,6 +1735,23 @@ QueryListGetPrimaryStmt(List *stmts)
return NULL;
}
static void
AcquireExecutorLocksOnPartitions(List *partitionOids, int lockmode,
bool acquire)
{
ListCell *lc;
foreach(lc, partitionOids)
{
Oid partOid = lfirst_oid(lc);
if (acquire)
LockRelationOid(partOid, lockmode);
else
UnlockRelationOid(partOid, lockmode);
}
}
/*
* AcquireExecutorLocks: acquire locks needed for execution of a cached plan;
* or release them if acquire is false.
@ -1748,6 +1765,8 @@ AcquireExecutorLocks(List *stmt_list, bool acquire)
{
PlannedStmt *plannedstmt = lfirst_node(PlannedStmt, lc1);
ListCell *lc2;
Index rti,
resultRelation = 0;
if (plannedstmt->commandType == CMD_UTILITY)
{
@ -1765,6 +1784,9 @@ AcquireExecutorLocks(List *stmt_list, bool acquire)
continue;
}
rti = 1;
if (plannedstmt->resultRelations)
resultRelation = linitial_int(plannedstmt->resultRelations);
foreach(lc2, plannedstmt->rtable)
{
RangeTblEntry *rte = (RangeTblEntry *) lfirst(lc2);
@ -1782,6 +1804,14 @@ AcquireExecutorLocks(List *stmt_list, bool acquire)
LockRelationOid(rte->relid, rte->rellockmode);
else
UnlockRelationOid(rte->relid, rte->rellockmode);
/* Lock partitions ahead of modifying them in parallel mode. */
if (rti == resultRelation &&
plannedstmt->partitionOids != NIL)
AcquireExecutorLocksOnPartitions(plannedstmt->partitionOids,
rte->rellockmode, acquire);
rti++;
}
}
}
@ -1990,7 +2020,8 @@ PlanCacheRelCallback(Datum arg, Oid relid)
if (plannedstmt->commandType == CMD_UTILITY)
continue; /* Ignore utility statements */
if ((relid == InvalidOid) ? plannedstmt->relationOids != NIL :
list_member_oid(plannedstmt->relationOids, relid))
(list_member_oid(plannedstmt->relationOids, relid) ||
list_member_oid(plannedstmt->partitionOids, relid)))
{
/* Invalidate the generic plan only */
plansource->gplan->is_valid = false;