database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-08-27 07:42:10 +03:00
Code Activity

Add a new GUC and a reloption to enable inserts in parallel-mode.

Browse Source 
Commit 05c8482f7f added the implementation of parallel SELECT for
"INSERT INTO ... SELECT ..." which may incur non-negligible overhead in
the additional parallel-safety checks that it performs, even when, in the
end, those checks determine that parallelism can't be used. This is
normally only ever a problem in the case of when the target table has a
large number of partitions.

A new GUC option "enable_parallel_insert" is added, to allow insert in
parallel-mode. The default is on.

In addition to the GUC option, the user may want a mechanism to allow
inserts in parallel-mode with finer granularity at table level. The new
table option "parallel_insert_enabled" allows this. The default is true.

Author: "Hou, Zhijie"
Reviewed-by: Greg Nancarrow, Amit Langote, Takayuki Tsunakawa, Amit Kapila
Discussion: https://postgr.es/m/CAA4eK1K-cW7svLC2D7DHoGHxdAdg3P37BLgebqBOC2ZLc9a6QQ%40mail.gmail.com
Discussion: https://postgr.es/m/CAJcOf-cXnB5cnMKqWEp2E2z7Mvcd04iLVmV=qpFJrR3AcrTS3g@mail.gmail.com
This commit is contained in:
Amit Kapila
2021-03-18 07:25:27 +05:30
parent 5f79580ad6
commit c8f78b6161
15 changed files with 240 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
src/backend/optimizer/path/costsize.c
View File

@@ -129,6 +129,8 @@ Cost disable_cost = 1.0e10;
int max_parallel_workers_per_gather = 2;
bool enable_parallel_insert = true;
bool enable_seqscan = true;
bool enable_indexscan = true;
bool enable_indexonlyscan = true;

34
src/backend/optimizer/util/clauses.c
View File

@@ -1265,8 +1265,10 @@ target_rel_chk_constr_max_parallel_hazard(Relation rel,
*
* It's not possible in the following cases:
*
* 1) INSERT...ON CONFLICT...DO UPDATE
* 2) INSERT without SELECT
* 1) enable_parallel_insert is off
* 2) INSERT...ON CONFLICT...DO UPDATE
* 3) INSERT without SELECT
* 4) the reloption parallel_insert_enabled is set to off
*
* (Note: we don't do in-depth parallel-safety checks here, we do only the
* cheaper tests that can quickly exclude obvious cases for which
@@ -1277,12 +1279,17 @@ bool
is_parallel_allowed_for_modify(Query *parse)
{
bool hasSubQuery;
bool parallel_enabled;
RangeTblEntry *rte;
ListCell *lc;
Relation rel;
if (!IsModifySupportedInParallelMode(parse->commandType))
return false;
if (!enable_parallel_insert)
return false;
/*
* UPDATE is not currently supported in parallel-mode, so prohibit
* INSERT...ON CONFLICT...DO UPDATE...
@@ -1313,7 +1320,28 @@ is_parallel_allowed_for_modify(Query *parse)
}
}
return hasSubQuery;
if (!hasSubQuery)
return false;
/*
* Check if parallel_insert_enabled is enabled for the target table, if
* not, skip the safety checks.
*
* (Note: if the target table is partitioned, the parallel_insert_enabled
* option setting of the partitions are ignored).
*/
rte = rt_fetch(parse->resultRelation, parse->rtable);
/*
* The target table is already locked by the caller (this is done in the
* parse/analyze phase), and remains locked until end-of-transaction.
*/
rel = table_open(rte->relid, NoLock);
parallel_enabled = RelationGetParallelInsert(rel, true);
table_close(rel, NoLock);
return parallel_enabled;
}
/*****************************************************************************