Thread

[PATCH] v3 parallel tid range scan: 1) corrected the startblock and numblock values when parallel tid range scan is used

Cary Huang <cary.huang@highgo.ca> — 2024-05-08T20:41:37Z

---
 src/backend/access/heap/heapam.c              | 14 ++++
 src/backend/access/table/tableam.c            | 31 ++++++-
 src/backend/executor/execParallel.c           | 20 +++++
 src/backend/executor/nodeTidrangescan.c       | 81 +++++++++++++++++++
 src/backend/optimizer/path/costsize.c         | 15 ++++
 src/backend/optimizer/path/tidpath.c          | 18 ++++-
 src/backend/optimizer/util/pathnode.c         |  7 +-
 src/include/access/relscan.h                  |  1 +
 src/include/access/tableam.h                  | 10 +++
 src/include/executor/nodeTidrangescan.h       |  7 ++
 src/include/nodes/execnodes.h                 |  1 +
 src/include/optimizer/pathnode.h              |  3 +-
 src/test/regress/expected/select_parallel.out | 51 ++++++++++++
 src/test/regress/sql/select_parallel.sql      | 15 ++++
 14 files changed, 268 insertions(+), 6 deletions(-)

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 4be0dee4de..a696cba458 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -307,6 +307,7 @@ initscan(HeapScanDesc scan, ScanKey key, bool keep_startblock)
 	 * results for a non-MVCC snapshot, the caller must hold some higher-level
 	 * lock that ensures the interesting tuple(s) won't change.)
 	 */
+
 	if (scan->rs_base.rs_parallel != NULL)
 	{
 		bpscan = (ParallelBlockTableScanDesc) scan->rs_base.rs_parallel;
@@ -1391,6 +1392,19 @@ heap_set_tidrange(TableScanDesc sscan, ItemPointer mintid,
 	/* Set the start block and number of blocks to scan */
 	heap_setscanlimits(sscan, startBlk, numBlks);
 
+	/*
+	 * if parallel mode is used, store startblock and numblocks in parallel
+	 * scan descriptor as well
+	 */
+	if (scan->rs_base.rs_parallel != NULL)
+	{
+		ParallelBlockTableScanDesc bpscan = NULL;
+
+		bpscan = (ParallelBlockTableScanDesc) scan->rs_base.rs_parallel;
+		bpscan->phs_startblock = scan->rs_startblock;
+		bpscan->phs_numblock = scan->rs_numblocks;
+	}
+
 	/* Finally, set the TID range in sscan */
 	ItemPointerCopy(&lowestItem, &sscan->rs_mintid);
 	ItemPointerCopy(&highestItem, &sscan->rs_maxtid);
diff --git a/src/backend/access/table/tableam.c b/src/backend/access/table/tableam.c
index e57a0b7ea3..61959d2b7d 100644
--- a/src/backend/access/table/tableam.c
+++ b/src/backend/access/table/tableam.c
@@ -187,6 +187,34 @@ table_beginscan_parallel(Relation relation, ParallelTableScanDesc pscan)
 											pscan, flags);
 }
 
+TableScanDesc
+table_beginscan_parallel_tidrange(Relation relation, ParallelTableScanDesc pscan)
+{
+	Snapshot	snapshot;
+	uint32		flags = SO_TYPE_TIDRANGESCAN | SO_ALLOW_PAGEMODE;
+	TableScanDesc sscan;
+
+	Assert(RelationGetRelid(relation) == pscan->phs_relid);
+
+	if (!pscan->phs_snapshot_any)
+	{
+		/* Snapshot was serialized -- restore it */
+		snapshot = RestoreSnapshot((char *) pscan + pscan->phs_snapshot_off);
+		RegisterSnapshot(snapshot);
+		flags |= SO_TEMP_SNAPSHOT;
+	}
+	else
+	{
+		/* SnapshotAny passed by caller (not serialized) */
+		snapshot = SnapshotAny;
+	}
+
+	sscan = relation->rd_tableam->scan_begin(relation, snapshot, 0, NULL,
+											 pscan, flags);
+
+	return sscan;
+}
+
 
 /* ----------------------------------------------------------------------------
  * Index scan related functions.
@@ -576,7 +604,8 @@ table_block_parallelscan_nextpage(Relation rel,
 		pbscanwork->phsw_chunk_remaining = pbscanwork->phsw_chunk_size - 1;
 	}
 
-	if (nallocated >= pbscan->phs_nblocks)
+	if (nallocated >= pbscan->phs_nblocks || (pbscan->phs_numblock != 0 &&
+		nallocated >= pbscan->phs_numblock))
 		page = InvalidBlockNumber;	/* all blocks have been allocated */
 	else
 		page = (nallocated + pbscan->phs_startblock) % pbscan->phs_nblocks;
diff --git a/src/backend/executor/execParallel.c b/src/backend/executor/execParallel.c
index 8c53d1834e..e4733ca5a3 100644
--- a/src/backend/executor/execParallel.c
+++ b/src/backend/executor/execParallel.c
@@ -40,6 +40,7 @@
 #include "executor/nodeSort.h"
 #include "executor/nodeSubplan.h"
 #include "executor/tqueue.h"
+#include "executor/nodeTidrangescan.h"
 #include "jit/jit.h"
 #include "nodes/nodeFuncs.h"
 #include "pgstat.h"
@@ -296,6 +297,11 @@ ExecParallelEstimate(PlanState *planstate, ExecParallelEstimateContext *e)
 			/* even when not parallel-aware, for EXPLAIN ANALYZE */
 			ExecMemoizeEstimate((MemoizeState *) planstate, e->pcxt);
 			break;
+		case T_TidRangeScanState:
+			if (planstate->plan->parallel_aware)
+				ExecTidRangeScanEstimate((TidRangeScanState *) planstate,
+									e->pcxt);
+			break;
 		default:
 			break;
 	}
@@ -520,6 +526,11 @@ ExecParallelInitializeDSM(PlanState *planstate,
 			/* even when not parallel-aware, for EXPLAIN ANALYZE */
 			ExecMemoizeInitializeDSM((MemoizeState *) planstate, d->pcxt);
 			break;
+		case T_TidRangeScanState:
+			if (planstate->plan->parallel_aware)
+				ExecTidRangeScanInitializeDSM((TidRangeScanState *) planstate,
+										 d->pcxt);
+			break;
 		default:
 			break;
 	}
@@ -1006,6 +1017,11 @@ ExecParallelReInitializeDSM(PlanState *planstate,
 		case T_MemoizeState:
 			/* these nodes have DSM state, but no reinitialization is required */
 			break;
+		case T_TidRangeScanState:
+			if (planstate->plan->parallel_aware)
+				ExecTidRangeScanReInitializeDSM((TidRangeScanState *) planstate,
+										   pcxt);
+			break;
 
 		default:
 			break;
@@ -1372,6 +1388,10 @@ ExecParallelInitializeWorker(PlanState *planstate, ParallelWorkerContext *pwcxt)
 			/* even when not parallel-aware, for EXPLAIN ANALYZE */
 			ExecMemoizeInitializeWorker((MemoizeState *) planstate, pwcxt);
 			break;
+		case T_TidRangeScanState:
+			if (planstate->plan->parallel_aware)
+				ExecTidRangeScanInitializeWorker((TidRangeScanState *) planstate, pwcxt);
+			break;
 		default:
 			break;
 	}
diff --git a/src/backend/executor/nodeTidrangescan.c b/src/backend/executor/nodeTidrangescan.c
index 9aa7683d7e..b1553b990d 100644
--- a/src/backend/executor/nodeTidrangescan.c
+++ b/src/backend/executor/nodeTidrangescan.c
@@ -403,3 +403,84 @@ ExecInitTidRangeScan(TidRangeScan *node, EState *estate, int eflags)
 	 */
 	return tidrangestate;
 }
+/* ----------------------------------------------------------------
+ *						Parallel Scan Support
+ * ----------------------------------------------------------------
+ */
+
+/* ----------------------------------------------------------------
+ *		ExecTidRangeScanEstimate
+ *
+ *		Compute the amount of space we'll need in the parallel
+ *		query DSM, and inform pcxt->estimator about our needs.
+ * ----------------------------------------------------------------
+ */
+void
+ExecTidRangeScanEstimate(TidRangeScanState *node,
+					ParallelContext *pcxt)
+{
+	EState	   *estate = node->ss.ps.state;
+
+	node->pscan_len = table_parallelscan_estimate(node->ss.ss_currentRelation,
+												  estate->es_snapshot);
+	shm_toc_estimate_chunk(&pcxt->estimator, node->pscan_len);
+	shm_toc_estimate_keys(&pcxt->estimator, 1);
+}
+
+/* ----------------------------------------------------------------
+ *		ExecTidRangeScanInitializeDSM
+ *
+ *		Set up a parallel heap scan descriptor.
+ * ----------------------------------------------------------------
+ */
+void
+ExecTidRangeScanInitializeDSM(TidRangeScanState *node,
+						 ParallelContext *pcxt)
+{
+	EState	   *estate = node->ss.ps.state;
+	ParallelTableScanDesc pscan;
+
+	pscan = shm_toc_allocate(pcxt->toc, node->pscan_len);
+	table_parallelscan_initialize(node->ss.ss_currentRelation,
+								  pscan,
+								  estate->es_snapshot);
+	/* disable syncscan in parallel tid range scan */
+	pscan->phs_syncscan = false;
+	shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, pscan);
+	node->ss.ss_currentScanDesc =
+		table_beginscan_parallel_tidrange(node->ss.ss_currentRelation, pscan);
+}
+
+/* ----------------------------------------------------------------
+ *		ExecTidRangeScanReInitializeDSM
+ *
+ *		Reset shared state before beginning a fresh scan.
+ * ----------------------------------------------------------------
+ */
+void
+ExecTidRangeScanReInitializeDSM(TidRangeScanState *node,
+						   ParallelContext *pcxt)
+{
+	ParallelTableScanDesc pscan;
+
+	pscan = node->ss.ss_currentScanDesc->rs_parallel;
+	table_parallelscan_reinitialize(node->ss.ss_currentRelation, pscan);
+
+}
+
+/* ----------------------------------------------------------------
+ *		ExecSeqScanInitializeWorker
+ *
+ *		Copy relevant information from TOC into planstate.
+ * ----------------------------------------------------------------
+ */
+void
+ExecTidRangeScanInitializeWorker(TidRangeScanState *node,
+							ParallelWorkerContext *pwcxt)
+{
+	ParallelTableScanDesc pscan;
+
+	pscan = shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false);
+	node->ss.ss_currentScanDesc =
+		table_beginscan_parallel_tidrange(node->ss.ss_currentRelation, pscan);
+}
diff --git a/src/backend/optimizer/path/costsize.c b/src/backend/optimizer/path/costsize.c
index ee23ed7835..fee603d048 100644
--- a/src/backend/optimizer/path/costsize.c
+++ b/src/backend/optimizer/path/costsize.c
@@ -1435,6 +1435,21 @@ cost_tidrangescan(Path *path, PlannerInfo *root,
 	startup_cost += path->pathtarget->cost.startup;
 	run_cost += path->pathtarget->cost.per_tuple * path->rows;
 
+	/* Adjust costing for parallelism, if used. */
+	if (path->parallel_workers > 0)
+	{
+		double		parallel_divisor = get_parallel_divisor(path);
+
+		/* The CPU cost is divided among all the workers. */
+		run_cost /= parallel_divisor;
+
+		/*
+		 * In the case of a parallel plan, the row count needs to represent
+		 * the number of tuples processed per worker.
+		 */
+		path->rows = clamp_row_est(path->rows / parallel_divisor);
+	}
+
 	path->startup_cost = startup_cost;
 	path->total_cost = startup_cost + run_cost;
 }
diff --git a/src/backend/optimizer/path/tidpath.c b/src/backend/optimizer/path/tidpath.c
index 2ae5ddfe43..3c52ef911e 100644
--- a/src/backend/optimizer/path/tidpath.c
+++ b/src/backend/optimizer/path/tidpath.c
@@ -46,6 +46,7 @@
 #include "optimizer/pathnode.h"
 #include "optimizer/paths.h"
 #include "optimizer/restrictinfo.h"
+#include "optimizer/cost.h"
 
 
 /*
@@ -496,7 +497,22 @@ create_tidscan_paths(PlannerInfo *root, RelOptInfo *rel)
 
 		add_path(rel, (Path *) create_tidrangescan_path(root, rel,
 														tidrangequals,
-														required_outer));
+														required_outer,
+														0));
+
+		/* If appropriate, consider parallel tid range scan */
+		if (rel->consider_parallel && required_outer == NULL)
+		{
+			int			parallel_workers;
+
+			parallel_workers = compute_parallel_worker(rel, rel->pages, -1,
+													   max_parallel_workers_per_gather);
+			if (parallel_workers > 0)
+			{
+				add_partial_path(rel, (Path *) create_tidrangescan_path(root, rel, tidrangequals,
+								required_outer, parallel_workers));
+			}
+		}
 	}
 
 	/*
diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index 3cf1dac087..7ceeaf8688 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -1206,7 +1206,8 @@ create_tidscan_path(PlannerInfo *root, RelOptInfo *rel, List *tidquals,
  */
 TidRangePath *
 create_tidrangescan_path(PlannerInfo *root, RelOptInfo *rel,
-						 List *tidrangequals, Relids required_outer)
+						 List *tidrangequals, Relids required_outer,
+						 int parallel_workers)
 {
 	TidRangePath *pathnode = makeNode(TidRangePath);
 
@@ -1215,9 +1216,9 @@ create_tidrangescan_path(PlannerInfo *root, RelOptInfo *rel,
 	pathnode->path.pathtarget = rel->reltarget;
 	pathnode->path.param_info = get_baserel_parampathinfo(root, rel,
 														  required_outer);
-	pathnode->path.parallel_aware = false;
+	pathnode->path.parallel_aware = (parallel_workers > 0);
 	pathnode->path.parallel_safe = rel->consider_parallel;
-	pathnode->path.parallel_workers = 0;
+	pathnode->path.parallel_workers = parallel_workers;
 	pathnode->path.pathkeys = NIL;	/* always unordered */
 
 	pathnode->tidrangequals = tidrangequals;
diff --git a/src/include/access/relscan.h b/src/include/access/relscan.h
index 521043304a..9bede2d6e6 100644
--- a/src/include/access/relscan.h
+++ b/src/include/access/relscan.h
@@ -81,6 +81,7 @@ typedef struct ParallelBlockTableScanDescData
 	BlockNumber phs_startblock; /* starting block number */
 	pg_atomic_uint64 phs_nallocated;	/* number of blocks allocated to
 										 * workers so far. */
+	BlockNumber phs_numblock; /* max number of blocks to scan */
 }			ParallelBlockTableScanDescData;
 typedef struct ParallelBlockTableScanDescData *ParallelBlockTableScanDesc;
 
diff --git a/src/include/access/tableam.h b/src/include/access/tableam.h
index 8e583b45cd..2cffd813a5 100644
--- a/src/include/access/tableam.h
+++ b/src/include/access/tableam.h
@@ -1175,6 +1175,16 @@ extern void table_parallelscan_initialize(Relation rel,
 extern TableScanDesc table_beginscan_parallel(Relation relation,
 											  ParallelTableScanDesc pscan);
 
+/*
+ * Begin a parallel tidrange scan. `pscan` needs to have been initialized with
+ * table_parallelscan_initialize(), for the same relation. The initialization
+ * does not need to have happened in this backend.
+ *
+ * Caller must hold a suitable lock on the relation.
+ */
+extern TableScanDesc table_beginscan_parallel_tidrange(Relation relation,
+													   ParallelTableScanDesc pscan);
+
 /*
  * Restart a parallel scan.  Call this in the leader process.  Caller is
  * responsible for making sure that all workers have finished the scan
diff --git a/src/include/executor/nodeTidrangescan.h b/src/include/executor/nodeTidrangescan.h
index 1cfc7a07be..977cb8eb6e 100644
--- a/src/include/executor/nodeTidrangescan.h
+++ b/src/include/executor/nodeTidrangescan.h
@@ -14,6 +14,7 @@
 #ifndef NODETIDRANGESCAN_H
 #define NODETIDRANGESCAN_H
 
+#include "access/parallel.h"
 #include "nodes/execnodes.h"
 
 extern TidRangeScanState *ExecInitTidRangeScan(TidRangeScan *node,
@@ -21,4 +22,10 @@ extern TidRangeScanState *ExecInitTidRangeScan(TidRangeScan *node,
 extern void ExecEndTidRangeScan(TidRangeScanState *node);
 extern void ExecReScanTidRangeScan(TidRangeScanState *node);
 
+/* parallel scan support */
+extern void ExecTidRangeScanEstimate(TidRangeScanState *node, ParallelContext *pcxt);
+extern void ExecTidRangeScanInitializeDSM(TidRangeScanState *node, ParallelContext *pcxt);
+extern void ExecTidRangeScanReInitializeDSM(TidRangeScanState *node, ParallelContext *pcxt);
+extern void ExecTidRangeScanInitializeWorker(TidRangeScanState *node, ParallelWorkerContext *pwcxt);
+
 #endif							/* NODETIDRANGESCAN_H */
diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h
index d927ac44a8..81eec34730 100644
--- a/src/include/nodes/execnodes.h
+++ b/src/include/nodes/execnodes.h
@@ -1862,6 +1862,7 @@ typedef struct TidRangeScanState
 	ItemPointerData trss_mintid;
 	ItemPointerData trss_maxtid;
 	bool		trss_inScan;
+	Size		pscan_len;		/* size of parallel tid range scan descriptor */
 } TidRangeScanState;
 
 /* ----------------
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index c5c4756b0f..d7683ec1c3 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -66,7 +66,8 @@ extern TidPath *create_tidscan_path(PlannerInfo *root, RelOptInfo *rel,
 extern TidRangePath *create_tidrangescan_path(PlannerInfo *root,
 											  RelOptInfo *rel,
 											  List *tidrangequals,
-											  Relids required_outer);
+											  Relids required_outer,
+											  int parallel_workers);
 extern AppendPath *create_append_path(PlannerInfo *root, RelOptInfo *rel,
 									  List *subpaths, List *partial_subpaths,
 									  List *pathkeys, Relids required_outer,
diff --git a/src/test/regress/expected/select_parallel.out b/src/test/regress/expected/select_parallel.out
index 87273fa635..61e6700194 100644
--- a/src/test/regress/expected/select_parallel.out
+++ b/src/test/regress/expected/select_parallel.out
@@ -1293,4 +1293,55 @@ SELECT 1 FROM tenk1_vw_sec
                  Filter: (f1 < tenk1_vw_sec.unique1)
 (9 rows)
 
+-- test parallel tid range scan
+EXPLAIN (COSTS OFF)
+SELECT ctid FROM tenk1 WHERE ctid > '(0,1)' LIMIT 1;
+                  QUERY PLAN                   
+-----------------------------------------------
+ Limit
+   ->  Gather
+         Workers Planned: 4
+         ->  Parallel Tid Range Scan on tenk1
+               TID Cond: (ctid > '(0,1)'::tid)
+(5 rows)
+
+EXPLAIN (COSTS OFF)
+SELECT ctid FROM tenk1 WHERE ctid < '(400,1)' LIMIT 1;
+                   QUERY PLAN                    
+-------------------------------------------------
+ Limit
+   ->  Gather
+         Workers Planned: 4
+         ->  Parallel Tid Range Scan on tenk1
+               TID Cond: (ctid < '(400,1)'::tid)
+(5 rows)
+
+EXPLAIN (COSTS OFF)
+SELECT ctid FROM tenk1 WHERE ctid >= '(0,1)' AND ctid <= '(400,1)' LIMIT 1;
+                                  QUERY PLAN                                   
+-------------------------------------------------------------------------------
+ Limit
+   ->  Gather
+         Workers Planned: 4
+         ->  Parallel Tid Range Scan on tenk1
+               TID Cond: ((ctid >= '(0,1)'::tid) AND (ctid <= '(400,1)'::tid))
+(5 rows)
+
+EXPLAIN (COSTS OFF)
+SELECT t.ctid,t2.c FROM tenk1 t,
+LATERAL (SELECT count(*) c FROM tenk1 t2 WHERE t2.ctid <= t.ctid) t2
+WHERE t.ctid < '(1,0)' LIMIT 1;
+                      QUERY PLAN                      
+------------------------------------------------------
+ Limit
+   ->  Nested Loop
+         ->  Gather
+               Workers Planned: 4
+               ->  Parallel Tid Range Scan on tenk1 t
+                     TID Cond: (ctid < '(1,0)'::tid)
+         ->  Aggregate
+               ->  Tid Range Scan on tenk1 t2
+                     TID Cond: (ctid <= t.ctid)
+(9 rows)
+
 rollback;
diff --git a/src/test/regress/sql/select_parallel.sql b/src/test/regress/sql/select_parallel.sql
index 20376c03fa..1d4ef68790 100644
--- a/src/test/regress/sql/select_parallel.sql
+++ b/src/test/regress/sql/select_parallel.sql
@@ -495,4 +495,19 @@ EXPLAIN (COSTS OFF)
 SELECT 1 FROM tenk1_vw_sec
   WHERE (SELECT sum(f1) FROM int4_tbl WHERE f1 < unique1) < 100;
 
+-- test parallel tid range scan
+EXPLAIN (COSTS OFF)
+SELECT ctid FROM tenk1 WHERE ctid > '(0,1)' LIMIT 1;
+
+EXPLAIN (COSTS OFF)
+SELECT ctid FROM tenk1 WHERE ctid < '(400,1)' LIMIT 1;
+
+EXPLAIN (COSTS OFF)
+SELECT ctid FROM tenk1 WHERE ctid >= '(0,1)' AND ctid <= '(400,1)' LIMIT 1;
+
+EXPLAIN (COSTS OFF)
+SELECT t.ctid,t2.c FROM tenk1 t,
+LATERAL (SELECT count(*) c FROM tenk1 t2 WHERE t2.ctid <= t.ctid) t2
+WHERE t.ctid < '(1,0)' LIMIT 1;
+
 rollback;
-- 
2.17.1


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