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

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To allow inserts in parallel-mode this feature has to ensure that all the
constraints, triggers, etc. are parallel-safe for the partition hierarchy
which is costly and we need to find a better way to do that. Additionally,
we could have used existing cached information in some cases like indexes,
domains, etc. to determine the parallel-safety.

List of commits reverted, in reverse chronological order:

ed62d3737c Doc: Update description for parallel insert reloption.
c8f78b6161 Add a new GUC and a reloption to enable inserts in parallel-mode.
c5be48f092 Improve FK trigger parallel-safety check added by 05c8482f7f.
e2cda3c20a Fix use of relcache TriggerDesc field introduced by commit 05c8482f7f.
e4e87a32cc Fix valgrind issue in commit 05c8482f7f.
05c8482f7f Enable parallel SELECT for "INSERT INTO ... SELECT ...".

Discussion: https://postgr.es/m/E1lMiB9-0001c3-SY@gemulon.postgresql.org
This commit is contained in:
Amit Kapila
2021-03-24 11:10:12 +05:30
parent 84007043fc
commit 26acb54a13
31 changed files with 35 additions and 1761 deletions
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37
src/backend/optimizer/plan/planner.c
View File

@@ -305,7 +305,6 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
glob->resultRelations = NIL;
glob->appendRelations = NIL;
glob->relationOids = NIL;
glob->partitionOids = NIL;
glob->invalItems = NIL;
glob->paramExecTypes = NIL;
glob->lastPHId = 0;
@@ -317,16 +316,16 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
/*
* Assess whether it's feasible to use parallel mode for this query. We
* can't do this in a standalone backend, or if the command will try to
* modify any data (except for Insert), or if this is a cursor operation,
* or if GUCs are set to values that don't permit parallelism, or if
* parallel-unsafe functions are present in the query tree.
* modify any data, or if this is a cursor operation, or if GUCs are set
* to values that don't permit parallelism, or if parallel-unsafe
* functions are present in the query tree.
*
* (Note that we do allow CREATE TABLE AS, INSERT INTO...SELECT, SELECT
* INTO, and CREATE MATERIALIZED VIEW to use parallel plans. However, as
* of now, only the leader backend writes into a completely new table. In
* the future, we can extend it to allow workers to write into the table.
* However, to allow parallel updates and deletes, we have to solve other
* problems, especially around combo CIDs.)
* (Note that we do allow CREATE TABLE AS, SELECT INTO, and CREATE
* MATERIALIZED VIEW to use parallel plans, but as of now, only the leader
* backend writes into a completely new table. In the future, we can
* extend it to allow workers to write into the table. However, to allow
* parallel updates and deletes, we have to solve other problems,
* especially around combo CIDs.)
*
* For now, we don't try to use parallel mode if we're running inside a
* parallel worker. We might eventually be able to relax this
@@ -335,14 +334,13 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
*/
if ((cursorOptions & CURSOR_OPT_PARALLEL_OK) != 0 &&
IsUnderPostmaster &&
(parse->commandType == CMD_SELECT ||
is_parallel_allowed_for_modify(parse)) &&
parse->commandType == CMD_SELECT &&
!parse->hasModifyingCTE &&
max_parallel_workers_per_gather > 0 &&
!IsParallelWorker())
{
/* all the cheap tests pass, so scan the query tree */
glob->maxParallelHazard = max_parallel_hazard(parse, glob);
glob->maxParallelHazard = max_parallel_hazard(parse);
glob->parallelModeOK = (glob->maxParallelHazard != PROPARALLEL_UNSAFE);
}
else
@@ -523,19 +521,6 @@ standard_planner(Query *parse, const char *query_string, int cursorOptions,
result->rewindPlanIDs = glob->rewindPlanIDs;
result->rowMarks = glob->finalrowmarks;
result->relationOids = glob->relationOids;
/*
* Register the Oids of parallel-safety-checked partitions as plan
* dependencies. This is only really needed in the case of a parallel plan
* so that if parallel-unsafe properties are subsequently defined on the
* partitions, the cached parallel plan will be invalidated, and a
* non-parallel plan will be generated.
*
* We also use this list to acquire locks on partitions before executing
* cached plan. See AcquireExecutorLocks().
*/
if (glob->partitionOids != NIL && glob->parallelModeNeeded)
result->partitionOids = glob->partitionOids;
result->invalItems = glob->invalItems;
result->paramExecTypes = glob->paramExecTypes;
/* utilityStmt should be null, but we might as well copy it */