diff options
Diffstat (limited to 'src/backend/access/heap/heapam.c')
| -rw-r--r-- | src/backend/access/heap/heapam.c | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index b12b583c4d9..6e433db039e 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -1206,7 +1206,15 @@ heap_beginscan(Relation relation, Snapshot snapshot, else cb = heap_scan_stream_read_next_serial; - scan->rs_read_stream = read_stream_begin_relation(READ_STREAM_SEQUENTIAL, + /* --- + * It is safe to use batchmode as the only locks taken by `cb` + * are never taken while waiting for IO: + * - SyncScanLock is used in the non-parallel case + * - in the parallel case, only spinlocks and atomics are used + * --- + */ + scan->rs_read_stream = read_stream_begin_relation(READ_STREAM_SEQUENTIAL | + READ_STREAM_USE_BATCHING, scan->rs_strategy, scan->rs_base.rs_rd, MAIN_FORKNUM, @@ -1216,6 +1224,12 @@ heap_beginscan(Relation relation, Snapshot snapshot, } else if (scan->rs_base.rs_flags & SO_TYPE_BITMAPSCAN) { + /* + * Currently we can't trivially use batching, due to the + * VM_ALL_VISIBLE check in bitmapheap_stream_read_next. While that + * could be made safe, we are about to remove the all-visible logic + * from bitmap scans due to its unsoundness. + */ scan->rs_read_stream = read_stream_begin_relation(READ_STREAM_DEFAULT, scan->rs_strategy, scan->rs_base.rs_rd, |