[PATCH] v4 parallel tid range scan: improve regression tests
Cary Huang <cary.huang@highgo.ca>
From: Cary Huang <cary.huang@highgo.ca>
To:
Date: 2024-05-14T21:14:34Z
Lists: pgsql-hackers
---
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/tidrangescan.out | 106 +++++++++++++++++++++
src/test/regress/sql/tidrangescan.sql | 45 +++++++++
14 files changed, 353 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/tidrangescan.out b/src/test/regress/expected/tidrangescan.out
index 721f3b94e0..7d48b430d3 100644
--- a/src/test/regress/expected/tidrangescan.out
+++ b/src/test/regress/expected/tidrangescan.out
@@ -297,4 +297,110 @@ FETCH LAST c;
COMMIT;
DROP TABLE tidrangescan;
+-- tests for parallel tidrangescans
+SET parallel_setup_cost=0;
+SET parallel_tuple_cost=0;
+SET min_parallel_table_scan_size=0;
+SET max_parallel_workers_per_gather=4;
+CREATE TABLE parallel_tidrangescan(id integer, data text) with (fillfactor=10);
+-- insert enough tuples such that each page gets 5 tuples with fillfactor = 10
+INSERT INTO parallel_tidrangescan SELECT i,repeat('x', 100) FROM generate_series(1,200) AS s(i);
+-- ensure there are 40 pages for parallel test
+select min(ctid), max(ctid) from parallel_tidrangescan;
+ min | max
+-------+--------
+ (0,1) | (39,5)
+(1 row)
+
+-- parallel range scans with upper bound
+explain (costs off)
+select count(*) from parallel_tidrangescan where ctid<'(30,1)';
+ QUERY PLAN
+--------------------------------------------------------------------
+ Finalize Aggregate
+ -> Gather
+ Workers Planned: 4
+ -> Partial Aggregate
+ -> Parallel Tid Range Scan on parallel_tidrangescan
+ TID Cond: (ctid < '(30,1)'::tid)
+(6 rows)
+
+select count(*) from parallel_tidrangescan where ctid<'(30,1)';
+ count
+-------
+ 150
+(1 row)
+
+-- parallel range scans with lower bound
+explain (costs off)
+select count(*) from parallel_tidrangescan where ctid>'(10,0)';
+ QUERY PLAN
+--------------------------------------------------------------------
+ Finalize Aggregate
+ -> Gather
+ Workers Planned: 4
+ -> Partial Aggregate
+ -> Parallel Tid Range Scan on parallel_tidrangescan
+ TID Cond: (ctid > '(10,0)'::tid)
+(6 rows)
+
+select count(*) from parallel_tidrangescan where ctid>'(10,0)';
+ count
+-------
+ 150
+(1 row)
+
+-- parallel range scans with both bounds
+explain (costs off)
+select count(*) from parallel_tidrangescan where ctid>'(10,0)' and ctid<'(30,1)';
+ QUERY PLAN
+-----------------------------------------------------------------------------------
+ Finalize Aggregate
+ -> Gather
+ Workers Planned: 4
+ -> Partial Aggregate
+ -> Parallel Tid Range Scan on parallel_tidrangescan
+ TID Cond: ((ctid > '(10,0)'::tid) AND (ctid < '(30,1)'::tid))
+(6 rows)
+
+select count(*) from parallel_tidrangescan where ctid>'(10,0)' and ctid<'(30,1)';
+ count
+-------
+ 100
+(1 row)
+
+-- parallel rescans
+EXPLAIN (COSTS OFF)
+SELECT t.ctid,t2.c FROM parallel_tidrangescan t,
+LATERAL (SELECT count(*) c FROM parallel_tidrangescan t2 WHERE t2.ctid <= t.ctid) t2
+WHERE t.ctid < '(1,0)';
+ QUERY PLAN
+----------------------------------------------------------------
+ Nested Loop
+ -> Gather
+ Workers Planned: 4
+ -> Parallel Tid Range Scan on parallel_tidrangescan t
+ TID Cond: (ctid < '(1,0)'::tid)
+ -> Aggregate
+ -> Tid Range Scan on parallel_tidrangescan t2
+ TID Cond: (ctid <= t.ctid)
+(8 rows)
+
+SELECT t.ctid,t2.c FROM parallel_tidrangescan t,
+LATERAL (SELECT count(*) c FROM parallel_tidrangescan t2 WHERE t2.ctid <= t.ctid) t2
+WHERE t.ctid < '(1,0)';
+ ctid | c
+-------+---
+ (0,1) | 1
+ (0,2) | 2
+ (0,3) | 3
+ (0,4) | 4
+ (0,5) | 5
+(5 rows)
+
+DROP TABLE parallel_tidrangescan;
+RESET parallel_setup_cost;
+RESET parallel_tuple_cost;
+RESET min_parallel_table_scan_size;
+RESET max_parallel_workers_per_gather;
RESET enable_seqscan;
diff --git a/src/test/regress/sql/tidrangescan.sql b/src/test/regress/sql/tidrangescan.sql
index ac09ebb626..5b9bf8efc7 100644
--- a/src/test/regress/sql/tidrangescan.sql
+++ b/src/test/regress/sql/tidrangescan.sql
@@ -98,4 +98,49 @@ COMMIT;
DROP TABLE tidrangescan;
+-- tests for parallel tidrangescans
+SET parallel_setup_cost=0;
+SET parallel_tuple_cost=0;
+SET min_parallel_table_scan_size=0;
+SET max_parallel_workers_per_gather=4;
+
+CREATE TABLE parallel_tidrangescan(id integer, data text) with (fillfactor=10);
+
+-- insert enough tuples such that each page gets 5 tuples with fillfactor = 10
+INSERT INTO parallel_tidrangescan SELECT i,repeat('x', 100) FROM generate_series(1,200) AS s(i);
+
+-- ensure there are 40 pages for parallel test
+select min(ctid), max(ctid) from parallel_tidrangescan;
+
+-- parallel range scans with upper bound
+explain (costs off)
+select count(*) from parallel_tidrangescan where ctid<'(30,1)';
+select count(*) from parallel_tidrangescan where ctid<'(30,1)';
+
+-- parallel range scans with lower bound
+explain (costs off)
+select count(*) from parallel_tidrangescan where ctid>'(10,0)';
+select count(*) from parallel_tidrangescan where ctid>'(10,0)';
+
+-- parallel range scans with both bounds
+explain (costs off)
+select count(*) from parallel_tidrangescan where ctid>'(10,0)' and ctid<'(30,1)';
+select count(*) from parallel_tidrangescan where ctid>'(10,0)' and ctid<'(30,1)';
+
+-- parallel rescans
+EXPLAIN (COSTS OFF)
+SELECT t.ctid,t2.c FROM parallel_tidrangescan t,
+LATERAL (SELECT count(*) c FROM parallel_tidrangescan t2 WHERE t2.ctid <= t.ctid) t2
+WHERE t.ctid < '(1,0)';
+
+SELECT t.ctid,t2.c FROM parallel_tidrangescan t,
+LATERAL (SELECT count(*) c FROM parallel_tidrangescan t2 WHERE t2.ctid <= t.ctid) t2
+WHERE t.ctid < '(1,0)';
+
+DROP TABLE parallel_tidrangescan;
+
+RESET parallel_setup_cost;
+RESET parallel_tuple_cost;
+RESET min_parallel_table_scan_size;
+RESET max_parallel_workers_per_gather;
RESET enable_seqscan;
--
2.17.1
------=_Part_5426285_2131212966.1715722423182--