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Commitaf52770

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Adjust design of per-worker parallel seqscan data struct
The design of the data structures which allow storage of the per-workermemory during parallel seq scans were not ideal. The work done in56788d2 required an additional data structure to allow workers toremember the range of pages that had been allocated to them forprocessing during a parallel seqscan. That commit added a void pointerfield to TableScanDescData to allow heapam to store the per-workerallocation information. However putting the field there made very littlesense given that we have AM specific structs for that, e.g.HeapScanDescData.Here we remove the void pointer field from TableScanDescData and add adedicated field for this purpose to HeapScanDescData.Previously we also allocated memory for this parallel per-worker data forall scans, regardless if it was a parallel scan or not. This was just awasted allocation for non-parallel scans, so here we make the allocationconditional on the scan being parallel.Also, add previously missing pfree() to free the per-worker data inheap_endscan().Reported-by: Andres FreundReviewed-by: Andres FreundDiscussion:https://postgr.es/m/20210317023101.anvejcfotwka6gaa@alap3.anarazel.de
1 parent6d7a6fe commitaf52770

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3 files changed

+22
-7
lines changed

3 files changed

+22
-7
lines changed

‎src/backend/access/heap/heapam.c

Lines changed: 16 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -540,7 +540,7 @@ heapgettup(HeapScanDesc scan,
540540
ParallelBlockTableScanDescpbscan=
541541
(ParallelBlockTableScanDesc)scan->rs_base.rs_parallel;
542542
ParallelBlockTableScanWorkerpbscanwork=
543-
(ParallelBlockTableScanWorker)scan->rs_base.rs_private;
543+
scan->rs_parallelworkerdata;
544544

545545
table_block_parallelscan_startblock_init(scan->rs_base.rs_rd,
546546
pbscanwork,pbscan);
@@ -748,7 +748,7 @@ heapgettup(HeapScanDesc scan,
748748
ParallelBlockTableScanDescpbscan=
749749
(ParallelBlockTableScanDesc)scan->rs_base.rs_parallel;
750750
ParallelBlockTableScanWorkerpbscanwork=
751-
(ParallelBlockTableScanWorker)scan->rs_base.rs_private;
751+
scan->rs_parallelworkerdata;
752752

753753
page=table_block_parallelscan_nextpage(scan->rs_base.rs_rd,
754754
pbscanwork,pbscan);
@@ -864,7 +864,7 @@ heapgettup_pagemode(HeapScanDesc scan,
864864
ParallelBlockTableScanDescpbscan=
865865
(ParallelBlockTableScanDesc)scan->rs_base.rs_parallel;
866866
ParallelBlockTableScanWorkerpbscanwork=
867-
(ParallelBlockTableScanWorker)scan->rs_base.rs_private;
867+
scan->rs_parallelworkerdata;
868868

869869
table_block_parallelscan_startblock_init(scan->rs_base.rs_rd,
870870
pbscanwork,pbscan);
@@ -1057,7 +1057,7 @@ heapgettup_pagemode(HeapScanDesc scan,
10571057
ParallelBlockTableScanDescpbscan=
10581058
(ParallelBlockTableScanDesc)scan->rs_base.rs_parallel;
10591059
ParallelBlockTableScanWorkerpbscanwork=
1060-
(ParallelBlockTableScanWorker)scan->rs_base.rs_private;
1060+
scan->rs_parallelworkerdata;
10611061

10621062
page=table_block_parallelscan_nextpage(scan->rs_base.rs_rd,
10631063
pbscanwork,pbscan);
@@ -1194,8 +1194,6 @@ heap_beginscan(Relation relation, Snapshot snapshot,
11941194
scan->rs_base.rs_nkeys=nkeys;
11951195
scan->rs_base.rs_flags=flags;
11961196
scan->rs_base.rs_parallel=parallel_scan;
1197-
scan->rs_base.rs_private=
1198-
palloc(sizeof(ParallelBlockTableScanWorkerData));
11991197
scan->rs_strategy=NULL;/* set in initscan */
12001198

12011199
/*
@@ -1231,6 +1229,15 @@ heap_beginscan(Relation relation, Snapshot snapshot,
12311229
/* we only need to set this up once */
12321230
scan->rs_ctup.t_tableOid=RelationGetRelid(relation);
12331231

1232+
/*
1233+
* Allocate memory to keep track of page allocation for parallel workers
1234+
* when doing a parallel scan.
1235+
*/
1236+
if (parallel_scan!=NULL)
1237+
scan->rs_parallelworkerdata=palloc(sizeof(ParallelBlockTableScanWorkerData));
1238+
else
1239+
scan->rs_parallelworkerdata=NULL;
1240+
12341241
/*
12351242
* we do this here instead of in initscan() because heap_rescan also calls
12361243
* initscan() and we don't want to allocate memory again
@@ -1306,6 +1313,9 @@ heap_endscan(TableScanDesc sscan)
13061313
if (scan->rs_strategy!=NULL)
13071314
FreeAccessStrategy(scan->rs_strategy);
13081315

1316+
if (scan->rs_parallelworkerdata!=NULL)
1317+
pfree(scan->rs_parallelworkerdata);
1318+
13091319
if (scan->rs_base.rs_flags&SO_TEMP_SNAPSHOT)
13101320
UnregisterSnapshot(scan->rs_base.rs_snapshot);
13111321

‎src/include/access/heapam.h

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -65,6 +65,12 @@ typedef struct HeapScanDescData
6565

6666
HeapTupleDatars_ctup;/* current tuple in scan, if any */
6767

68+
/*
69+
* For parallel scans to store page allocation data. NULL when not
70+
* performing a parallel scan.
71+
*/
72+
ParallelBlockTableScanWorkerData*rs_parallelworkerdata;
73+
6874
/* these fields only used in page-at-a-time mode and for bitmap scans */
6975
intrs_cindex;/* current tuple's index in vistuples */
7076
intrs_ntuples;/* number of visible tuples on page */

‎src/include/access/relscan.h

Lines changed: 0 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -46,7 +46,6 @@ typedef struct TableScanDescData
4646
*/
4747
uint32rs_flags;
4848

49-
void*rs_private;/* per-worker private memory for AM to use */
5049
structParallelTableScanDescData*rs_parallel;/* parallel scan
5150
* information */
5251
}TableScanDescData;

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