From d6dd6eb21dcfbc41208f87d1d81ffe3960130889 Mon Sep 17 00:00:00 2001 From: Melanie Plageman Date: Mon, 12 Feb 2024 18:50:29 -0500 Subject: [PATCH v1 03/11] BitmapHeapScan begin scan after bitmap setup There is no reason for table_beginscan_bm() to begin the actual scan of the underlying table in ExecInitBitmapHeapScan(). We can begin the underlying table scan after the index scan has been completed and the bitmap built. The one use of the scan descriptor during initialization was ExecBitmapHeapInitializeWorker(), which set the scan descriptor snapshot with one from an array in the parallel state. This overwrote the snapshot set in table_beginscan_bm(). By saving that worker snapshot as a member in the BitmapHeapScanState during initialization, it can be restored in table_beginscan_bm() after returning from the table AM specific begin scan function. --- src/backend/executor/nodeBitmapHeapscan.c | 27 ++++++++++++++--------- src/include/access/tableam.h | 18 +++++++++------ src/include/nodes/execnodes.h | 2 ++ 3 files changed, 30 insertions(+), 17 deletions(-) diff --git a/src/backend/executor/nodeBitmapHeapscan.c b/src/backend/executor/nodeBitmapHeapscan.c index 76382c91fd7..fd697d16c72 100644 --- a/src/backend/executor/nodeBitmapHeapscan.c +++ b/src/backend/executor/nodeBitmapHeapscan.c @@ -191,6 +191,17 @@ BitmapHeapNext(BitmapHeapScanState *node) } #endif /* USE_PREFETCH */ } + + if (!scan) + { + scan = node->ss.ss_currentScanDesc = table_beginscan_bm( + node->ss.ss_currentRelation, + node->ss.ps.state->es_snapshot, + node->worker_snapshot, + 0, + NULL); + } + node->initialized = true; } @@ -614,7 +625,8 @@ ExecReScanBitmapHeapScan(BitmapHeapScanState *node) PlanState *outerPlan = outerPlanState(node); /* rescan to release any page pin */ - table_rescan(node->ss.ss_currentScanDesc, NULL); + if (node->ss.ss_currentScanDesc) + table_rescan(node->ss.ss_currentScanDesc, NULL); /* release bitmaps and buffers if any */ if (node->tbmiterator) @@ -691,7 +703,8 @@ ExecEndBitmapHeapScan(BitmapHeapScanState *node) /* * close heap scan */ - table_endscan(scanDesc); + if (scanDesc) + table_endscan(scanDesc); } /* ---------------------------------------------------------------- @@ -740,6 +753,7 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags) scanstate->shared_prefetch_iterator = NULL; scanstate->pstate = NULL; scanstate->can_skip_fetch = false; + scanstate->worker_snapshot = NULL; /* * Miscellaneous initialization @@ -788,11 +802,6 @@ ExecInitBitmapHeapScan(BitmapHeapScan *node, EState *estate, int eflags) scanstate->ss.ss_currentRelation = currentRelation; - scanstate->ss.ss_currentScanDesc = table_beginscan_bm(currentRelation, - estate->es_snapshot, - 0, - NULL); - /* * all done. */ @@ -931,13 +940,11 @@ ExecBitmapHeapInitializeWorker(BitmapHeapScanState *node, ParallelWorkerContext *pwcxt) { ParallelBitmapHeapState *pstate; - Snapshot snapshot; Assert(node->ss.ps.state->es_query_dsa != NULL); pstate = shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false); node->pstate = pstate; - snapshot = RestoreSnapshot(pstate->phs_snapshot_data); - table_scan_update_snapshot(node->ss.ss_currentScanDesc, snapshot); + node->worker_snapshot = RestoreSnapshot(pstate->phs_snapshot_data); } diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h index 4d495216f07..77f32a7472d 100644 --- a/src/include/access/tableam.h +++ b/src/include/access/tableam.h @@ -931,6 +931,11 @@ table_beginscan_strat(Relation rel, Snapshot snapshot, return rel->rd_tableam->scan_begin(rel, snapshot, nkeys, key, NULL, flags); } +/* + * Update snapshot used by the scan. + */ +extern void table_scan_update_snapshot(TableScanDesc scan, Snapshot snapshot); + /* * table_beginscan_bm is an alternative entry point for setting up a * TableScanDesc for a bitmap heap scan. Although that scan technology is @@ -938,12 +943,16 @@ table_beginscan_strat(Relation rel, Snapshot snapshot, * make it worth using the same data structure. */ static inline TableScanDesc -table_beginscan_bm(Relation rel, Snapshot snapshot, +table_beginscan_bm(Relation rel, Snapshot snapshot, Snapshot worker_snapshot, int nkeys, struct ScanKeyData *key) { + TableScanDesc result; uint32 flags = SO_TYPE_BITMAPSCAN | SO_ALLOW_PAGEMODE; - return rel->rd_tableam->scan_begin(rel, snapshot, nkeys, key, NULL, flags); + result = rel->rd_tableam->scan_begin(rel, snapshot, nkeys, key, NULL, flags); + if (worker_snapshot) + table_scan_update_snapshot(result, worker_snapshot); + return result; } /* @@ -1033,11 +1042,6 @@ table_rescan_set_params(TableScanDesc scan, struct ScanKeyData *key, allow_pagemode); } -/* - * Update snapshot used by the scan. - */ -extern void table_scan_update_snapshot(TableScanDesc scan, Snapshot snapshot); - /* * Return next tuple from `scan`, store in slot. */ diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h index 444a5f0fd57..00c75fb10e2 100644 --- a/src/include/nodes/execnodes.h +++ b/src/include/nodes/execnodes.h @@ -1726,6 +1726,7 @@ typedef struct ParallelBitmapHeapState * shared_tbmiterator shared iterator * shared_prefetch_iterator shared iterator for prefetching * pstate shared state for parallel bitmap scan + * worker_snapshot snapshot for parallel worker * ---------------- */ typedef struct BitmapHeapScanState @@ -1750,6 +1751,7 @@ typedef struct BitmapHeapScanState TBMSharedIterator *shared_tbmiterator; TBMSharedIterator *shared_prefetch_iterator; ParallelBitmapHeapState *pstate; + Snapshot worker_snapshot; } BitmapHeapScanState; /* ---------------- -- 2.37.2