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Commite415831

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Mop-up for parallel degree-ectomy.
Fix a couple of overlooked uses of "degree" terminology. Make the parallelworker count selection logic in create_plain_partial_paths more robust (inparticular, it failed with max_parallel_workers_per_gather set to zero).
1 parentc9ce4a1 commite415831

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3 files changed

+26
-29
lines changed

3 files changed

+26
-29
lines changed

‎src/backend/optimizer/path/allpaths.c‎

Lines changed: 18 additions & 22 deletions
Original file line numberDiff line numberDiff line change
@@ -669,27 +669,14 @@ set_plain_rel_pathlist(PlannerInfo *root, RelOptInfo *rel, RangeTblEntry *rte)
669669
staticvoid
670670
create_plain_partial_paths(PlannerInfo*root,RelOptInfo*rel)
671671
{
672-
intparallel_workers=1;
672+
intparallel_workers;
673673

674674
/*
675-
* If the user has set the parallel_workers reloption,we decide what to do
676-
*based on the value ofthat option. Otherwise, we estimate a value.
675+
* If the user has set the parallel_workers reloption,use that; otherwise
676+
*select a default number ofworkers.
677677
*/
678678
if (rel->rel_parallel_workers!=-1)
679-
{
680-
/*
681-
* If parallel_workers = 0 is set for this relation, bail out. The
682-
* user does not want a parallel path for this relation.
683-
*/
684-
if (rel->rel_parallel_workers==0)
685-
return;
686-
687-
/*
688-
* Use the table parallel_workers, but don't go further than
689-
* max_parallel_workers_per_gather.
690-
*/
691-
parallel_workers=Min(rel->rel_parallel_workers,max_parallel_workers_per_gather);
692-
}
679+
parallel_workers=rel->rel_parallel_workers;
693680
else
694681
{
695682
intparallel_threshold=1000;
@@ -706,20 +693,29 @@ create_plain_partial_paths(PlannerInfo *root, RelOptInfo *rel)
706693
return;
707694

708695
/*
709-
*Limit thedegree ofparallelism logarithmicallybased on the size
710-
*of therelation. This probably needs to be a good deal more
696+
*Select thenumber ofworkersbased on thelog of thesize of the
697+
* relation. This probably needs to be a good deal more
711698
* sophisticated, but we need something here for now.
712699
*/
713-
while (rel->pages>parallel_threshold*3&&
714-
parallel_workers<max_parallel_workers_per_gather)
700+
parallel_workers=1;
701+
while (rel->pages>parallel_threshold*3)
715702
{
716703
parallel_workers++;
717704
parallel_threshold *=3;
718705
if (parallel_threshold >=PG_INT32_MAX /3)
719-
break;
706+
break;/* avoid overflow */
720707
}
721708
}
722709

710+
/*
711+
* In no case use more than max_parallel_workers_per_gather workers.
712+
*/
713+
parallel_workers=Min(parallel_workers,max_parallel_workers_per_gather);
714+
715+
/* If any limit was set to zero, the user doesn't want a parallel scan. */
716+
if (parallel_workers <=0)
717+
return;
718+
723719
/* Add an unordered partial path based on a parallel sequential scan. */
724720
add_partial_path(rel,create_seqscan_path(root,rel,NULL,parallel_workers));
725721
}

‎src/backend/optimizer/util/plancat.c‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -128,8 +128,8 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
128128
estimate_rel_size(relation,rel->attr_widths-rel->min_attr,
129129
&rel->pages,&rel->tuples,&rel->allvisfrac);
130130

131-
/*Retrive the parallel_workers reloption,if set. */
132-
rel->rel_parallel_workers=RelationGetParallelDegree(relation,-1);
131+
/*Retrieve the parallel_workers reloption,or -1 if not set. */
132+
rel->rel_parallel_workers=RelationGetParallelWorkers(relation,-1);
133133

134134
/*
135135
* Make list of indexes. Ignore indexes on system catalogs if told to.

‎src/include/utils/rel.h‎

Lines changed: 6 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -235,19 +235,20 @@ typedef struct StdRdOptions
235235
/*
236236
* RelationIsUsedAsCatalogTable
237237
*Returns whether the relation should be treated as a catalog table
238-
*from the pov of logical decoding. Note multiple evalor argument!
238+
*from the pov of logical decoding. Note multiple evalof argument!
239239
*/
240240
#defineRelationIsUsedAsCatalogTable(relation)\
241241
((relation)->rd_options ?\
242242
((StdRdOptions *) (relation)->rd_options)->user_catalog_table : false)
243243

244244
/*
245-
* RelationGetParallelDegree
246-
*Returns the relation's parallel_workers. Note multiple eval of argument!
245+
* RelationGetParallelWorkers
246+
*Returns the relation's parallel_workers reloption setting.
247+
*Note multiple eval of argument!
247248
*/
248-
#defineRelationGetParallelDegree(relation,defaultpd) \
249+
#defineRelationGetParallelWorkers(relation,defaultpw) \
249250
((relation)->rd_options ? \
250-
((StdRdOptions *) (relation)->rd_options)->parallel_workers : (defaultpd))
251+
((StdRdOptions *) (relation)->rd_options)->parallel_workers : (defaultpw))
251252

252253

253254
/*

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