From 05c8482f7f69a954fd65fce85f896e848fc48197 Mon Sep 17 00:00:00 2001 From: Amit Kapila Date: Wed, 10 Mar 2021 07:38:58 +0530 Subject: 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 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 --- src/backend/utils/cache/plancache.c | 33 ++++++++++++++++++++++++++++++++- 1 file changed, 32 insertions(+), 1 deletion(-) (limited to 'src/backend/utils/cache') diff --git a/src/backend/utils/cache/plancache.c b/src/backend/utils/cache/plancache.c index 1a0950489d7..c1f4128445b 100644 --- a/src/backend/utils/cache/plancache.c +++ b/src/backend/utils/cache/plancache.c @@ -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; -- cgit v1.2.3