within each worker process.
</para>
</listitem>
+ <listitem>
+ <para>
+ In a <emphasis>parallel tid range scan</emphasis>, the range of blocks
+ will be subdivided into smaller ranges which are shared among the
+ cooperating processes. Each worker process will complete the scanning
+ of its given range of blocks before requesting an additional range of
+ blocks.
+ </para>
+ </listitem>
</itemizedlist>
Other scan types, such as scans of non-btree indexes, may support
/* parallel scan */
table_block_parallelscan_startblock_init(scan->rs_base.rs_rd,
scan->rs_parallelworkerdata,
- (ParallelBlockTableScanDesc) scan->rs_base.rs_parallel);
+ (ParallelBlockTableScanDesc) scan->rs_base.rs_parallel,
+ scan->rs_startblock,
+ scan->rs_numblocks);
/* may return InvalidBlockNumber if there are no more blocks */
scan->rs_prefetch_block = table_block_parallelscan_nextpage(scan->rs_base.rs_rd,
pscan, flags);
}
+TableScanDesc
+table_beginscan_parallel_tidrange(Relation relation,
+ ParallelTableScanDesc pscan)
+{
+ Snapshot snapshot;
+ uint32 flags = SO_TYPE_TIDRANGESCAN | SO_ALLOW_PAGEMODE;
+ TableScanDesc sscan;
+
+ Assert(RelFileLocatorEquals(relation->rd_locator, pscan->phs_locator));
+
+ /* disable syncscan in parallel tid range scan. */
+ pscan->phs_syncscan = false;
+
+ 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.
bpscan->phs_nblocks > NBuffers / 4;
SpinLockInit(&bpscan->phs_mutex);
bpscan->phs_startblock = InvalidBlockNumber;
+ bpscan->phs_numblock = InvalidBlockNumber;
pg_atomic_init_u64(&bpscan->phs_nallocated, 0);
return sizeof(ParallelBlockTableScanDescData);
*
* Determine where the parallel seq scan should start. This function may be
* called many times, once by each parallel worker. We must be careful only
- * to set the startblock once.
+ * to set the phs_startblock and phs_numblock fields once.
+ *
+ * Callers may optionally specify a non-InvalidBlockNumber value for
+ * 'startblock' to force the scan to start at the given page. Likewise,
+ * 'numblocks' can be specified as a non-InvalidBlockNumber to limit the
+ * number of blocks to scan to that many blocks.
*/
void
table_block_parallelscan_startblock_init(Relation rel,
ParallelBlockTableScanWorker pbscanwork,
- ParallelBlockTableScanDesc pbscan)
+ ParallelBlockTableScanDesc pbscan,
+ BlockNumber startblock,
+ BlockNumber numblocks)
{
BlockNumber sync_startpage = InvalidBlockNumber;
+ BlockNumber scan_nblocks;
/* Reset the state we use for controlling allocation size. */
memset(pbscanwork, 0, sizeof(*pbscanwork));
StaticAssertStmt(MaxBlockNumber <= 0xFFFFFFFE,
"pg_nextpower2_32 may be too small for non-standard BlockNumber width");
- /*
- * We determine the chunk size based on the size of the relation. First we
- * split the relation into PARALLEL_SEQSCAN_NCHUNKS chunks but we then
- * take the next highest power of 2 number of the chunk size. This means
- * we split the relation into somewhere between PARALLEL_SEQSCAN_NCHUNKS
- * and PARALLEL_SEQSCAN_NCHUNKS / 2 chunks.
- */
- pbscanwork->phsw_chunk_size = pg_nextpower2_32(Max(pbscan->phs_nblocks /
- PARALLEL_SEQSCAN_NCHUNKS, 1));
-
- /*
- * Ensure we don't go over the maximum chunk size with larger tables. This
- * means we may get much more than PARALLEL_SEQSCAN_NCHUNKS for larger
- * tables. Too large a chunk size has been shown to be detrimental to
- * synchronous scan performance.
- */
- pbscanwork->phsw_chunk_size = Min(pbscanwork->phsw_chunk_size,
- PARALLEL_SEQSCAN_MAX_CHUNK_SIZE);
-
retry:
/* Grab the spinlock. */
SpinLockAcquire(&pbscan->phs_mutex);
/*
- * If the scan's startblock has not yet been initialized, we must do so
- * now. If this is not a synchronized scan, we just start at block 0, but
- * if it is a synchronized scan, we must get the starting position from
- * the synchronized scan machinery. We can't hold the spinlock while
- * doing that, though, so release the spinlock, get the information we
- * need, and retry. If nobody else has initialized the scan in the
- * meantime, we'll fill in the value we fetched on the second time
- * through.
+ * When the caller specified a limit on the number of blocks to scan, set
+ * that in the ParallelBlockTableScanDesc, if it's not been done by
+ * another worker already.
+ */
+ if (numblocks != InvalidBlockNumber &&
+ pbscan->phs_numblock == InvalidBlockNumber)
+ {
+ pbscan->phs_numblock = numblocks;
+ }
+
+ /*
+ * If the scan's phs_startblock has not yet been initialized, we must do
+ * so now. If a startblock was specified, start there, otherwise if this
+ * is not a synchronized scan, we just start at block 0, but if it is a
+ * synchronized scan, we must get the starting position from the
+ * synchronized scan machinery. We can't hold the spinlock while doing
+ * that, though, so release the spinlock, get the information we need, and
+ * retry. If nobody else has initialized the scan in the meantime, we'll
+ * fill in the value we fetched on the second time through.
*/
if (pbscan->phs_startblock == InvalidBlockNumber)
{
- if (!pbscan->base.phs_syncscan)
+ if (startblock != InvalidBlockNumber)
+ pbscan->phs_startblock = startblock;
+ else if (!pbscan->base.phs_syncscan)
pbscan->phs_startblock = 0;
else if (sync_startpage != InvalidBlockNumber)
pbscan->phs_startblock = sync_startpage;
}
}
SpinLockRelease(&pbscan->phs_mutex);
+
+ /*
+ * Figure out how many blocks we're going to scan; either all of them, or
+ * just phs_numblock's worth, if a limit has been imposed.
+ */
+ if (pbscan->phs_numblock == InvalidBlockNumber)
+ scan_nblocks = pbscan->phs_nblocks;
+ else
+ scan_nblocks = pbscan->phs_numblock;
+
+ /*
+ * We determine the chunk size based on scan_nblocks. First we split
+ * scan_nblocks into PARALLEL_SEQSCAN_NCHUNKS chunks then we calculate the
+ * next highest power of 2 number of the result. This means we split the
+ * blocks we're scanning into somewhere between PARALLEL_SEQSCAN_NCHUNKS
+ * and PARALLEL_SEQSCAN_NCHUNKS / 2 chunks.
+ */
+ pbscanwork->phsw_chunk_size = pg_nextpower2_32(Max(scan_nblocks /
+ PARALLEL_SEQSCAN_NCHUNKS, 1));
+
+ /*
+ * Ensure we don't go over the maximum chunk size with larger tables. This
+ * means we may get much more than PARALLEL_SEQSCAN_NCHUNKS for larger
+ * tables. Too large a chunk size has been shown to be detrimental to
+ * sequential scan performance.
+ */
+ pbscanwork->phsw_chunk_size = Min(pbscanwork->phsw_chunk_size,
+ PARALLEL_SEQSCAN_MAX_CHUNK_SIZE);
}
/*
ParallelBlockTableScanWorker pbscanwork,
ParallelBlockTableScanDesc pbscan)
{
+ BlockNumber scan_nblocks;
BlockNumber page;
uint64 nallocated;
*
* Here we name these ranges of blocks "chunks". The initial size of
* these chunks is determined in table_block_parallelscan_startblock_init
- * based on the size of the relation. Towards the end of the scan, we
+ * based on the number of blocks to scan. Towards the end of the scan, we
* start making reductions in the size of the chunks in order to attempt
* to divide the remaining work over all the workers as evenly as
* possible.
* phs_nallocated counter will exceed rs_nblocks, because workers will
* still increment the value, when they try to allocate the next block but
* all blocks have been allocated already. The counter must be 64 bits
- * wide because of that, to avoid wrapping around when rs_nblocks is close
- * to 2^32.
+ * wide because of that, to avoid wrapping around when scan_nblocks is
+ * close to 2^32.
*
* The actual block to return is calculated by adding the counter to the
- * starting block number, modulo nblocks.
+ * starting block number, modulo phs_nblocks.
*/
+ /* First, figure out how many blocks we're planning on scanning */
+ if (pbscan->phs_numblock == InvalidBlockNumber)
+ scan_nblocks = pbscan->phs_nblocks;
+ else
+ scan_nblocks = pbscan->phs_numblock;
+
/*
- * First check if we have any remaining blocks in a previous chunk for
- * this worker. We must consume all of the blocks from that before we
- * allocate a new chunk to the worker.
+ * Now check if we have any remaining blocks in a previous chunk for this
+ * worker. We must consume all of the blocks from that before we allocate
+ * a new chunk to the worker.
*/
if (pbscanwork->phsw_chunk_remaining > 0)
{
* chunk size set to 1.
*/
if (pbscanwork->phsw_chunk_size > 1 &&
- pbscanwork->phsw_nallocated > pbscan->phs_nblocks -
+ pbscanwork->phsw_nallocated > scan_nblocks -
(pbscanwork->phsw_chunk_size * PARALLEL_SEQSCAN_RAMPDOWN_CHUNKS))
pbscanwork->phsw_chunk_size >>= 1;
pbscanwork->phsw_chunk_remaining = pbscanwork->phsw_chunk_size - 1;
}
- if (nallocated >= pbscan->phs_nblocks)
+ /* Check if we've run out of blocks to scan */
+ if (nallocated >= scan_nblocks)
page = InvalidBlockNumber; /* all blocks have been allocated */
else
page = (nallocated + pbscan->phs_startblock) % pbscan->phs_nblocks;
#include "executor/nodeSeqscan.h"
#include "executor/nodeSort.h"
#include "executor/nodeSubplan.h"
+#include "executor/nodeTidrangescan.h"
#include "executor/tqueue.h"
#include "jit/jit.h"
#include "nodes/nodeFuncs.h"
ExecForeignScanEstimate((ForeignScanState *) planstate,
e->pcxt);
break;
+ case T_TidRangeScanState:
+ if (planstate->plan->parallel_aware)
+ ExecTidRangeScanEstimate((TidRangeScanState *) planstate,
+ e->pcxt);
+ break;
case T_AppendState:
if (planstate->plan->parallel_aware)
ExecAppendEstimate((AppendState *) planstate,
ExecForeignScanInitializeDSM((ForeignScanState *) planstate,
d->pcxt);
break;
+ case T_TidRangeScanState:
+ if (planstate->plan->parallel_aware)
+ ExecTidRangeScanInitializeDSM((TidRangeScanState *) planstate,
+ d->pcxt);
+ break;
case T_AppendState:
if (planstate->plan->parallel_aware)
ExecAppendInitializeDSM((AppendState *) planstate,
ExecForeignScanReInitializeDSM((ForeignScanState *) planstate,
pcxt);
break;
+ case T_TidRangeScanState:
+ if (planstate->plan->parallel_aware)
+ ExecTidRangeScanReInitializeDSM((TidRangeScanState *) planstate,
+ pcxt);
+ break;
case T_AppendState:
if (planstate->plan->parallel_aware)
ExecAppendReInitializeDSM((AppendState *) planstate, pcxt);
ExecForeignScanInitializeWorker((ForeignScanState *) planstate,
pwcxt);
break;
+ case T_TidRangeScanState:
+ if (planstate->plan->parallel_aware)
+ ExecTidRangeScanInitializeWorker((TidRangeScanState *) planstate,
+ pwcxt);
+ break;
case T_AppendState:
if (planstate->plan->parallel_aware)
ExecAppendInitializeWorker((AppendState *) planstate, pwcxt);
*/
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->trss_pscanlen =
+ table_parallelscan_estimate(node->ss.ss_currentRelation,
+ estate->es_snapshot);
+ shm_toc_estimate_chunk(&pcxt->estimator, node->trss_pscanlen);
+ shm_toc_estimate_keys(&pcxt->estimator, 1);
+}
+
+/* ----------------------------------------------------------------
+ * ExecTidRangeScanInitializeDSM
+ *
+ * Set up a parallel TID range scan descriptor.
+ * ----------------------------------------------------------------
+ */
+void
+ExecTidRangeScanInitializeDSM(TidRangeScanState *node, ParallelContext *pcxt)
+{
+ EState *estate = node->ss.ps.state;
+ ParallelTableScanDesc pscan;
+
+ pscan = shm_toc_allocate(pcxt->toc, node->trss_pscanlen);
+ table_parallelscan_initialize(node->ss.ss_currentRelation,
+ pscan,
+ estate->es_snapshot);
+ 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);
+}
+
+/* ----------------------------------------------------------------
+ * ExecTidRangeScanInitializeWorker
+ *
+ * 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);
+}
{
Selectivity selectivity;
double pages;
- Cost startup_cost = 0;
- Cost run_cost = 0;
+ Cost startup_cost;
+ Cost cpu_run_cost;
+ Cost disk_run_cost;
QualCost qpqual_cost;
Cost cpu_per_tuple;
QualCost tid_qual_cost;
* page is just a normal sequential page read. NOTE: it's desirable for
* TID Range Scans to cost more than the equivalent Sequential Scans,
* because Seq Scans have some performance advantages such as scan
- * synchronization and parallelizability, and we'd prefer one of them to
- * be picked unless a TID Range Scan really is better.
+ * synchronization, and we'd prefer one of them to be picked unless a TID
+ * Range Scan really is better.
*/
ntuples = selectivity * baserel->tuples;
nseqpages = pages - 1.0;
&spc_seq_page_cost);
/* disk costs; 1 random page and the remainder as seq pages */
- run_cost += spc_random_page_cost + spc_seq_page_cost * nseqpages;
+ disk_run_cost = spc_random_page_cost + spc_seq_page_cost * nseqpages;
/* Add scanning CPU costs */
get_restriction_qual_cost(root, baserel, param_info, &qpqual_cost);
* can't be removed, this is a mistake and we're going to underestimate
* the CPU cost a bit.)
*/
- startup_cost += qpqual_cost.startup + tid_qual_cost.per_tuple;
+ startup_cost = qpqual_cost.startup + tid_qual_cost.per_tuple;
cpu_per_tuple = cpu_tuple_cost + qpqual_cost.per_tuple -
tid_qual_cost.per_tuple;
- run_cost += cpu_per_tuple * ntuples;
+ cpu_run_cost = cpu_per_tuple * ntuples;
/* tlist eval costs are paid per output row, not per tuple scanned */
startup_cost += path->pathtarget->cost.startup;
- run_cost += path->pathtarget->cost.per_tuple * path->rows;
+ cpu_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. */
+ cpu_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);
+ }
/* we should not generate this path type when enable_tidscan=false */
Assert(enable_tidscan);
path->disabled_nodes = 0;
path->startup_cost = startup_cost;
- path->total_cost = startup_cost + run_cost;
+ path->total_cost = startup_cost + cpu_run_cost + disk_run_cost;
}
/*
/*
* create_tidscan_paths
- * Create paths corresponding to direct TID scans of the given rel.
- *
- * Candidate paths are added to the rel's pathlist (using add_path).
+ * Create paths corresponding to direct TID scans of the given rel and add
+ * them to the corresponding path list via add_path or add_partial_path.
*/
bool
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));
+ }
}
/*
*/
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);
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;
BlockNumber phs_nblocks; /* # blocks in relation at start of scan */
slock_t phs_mutex; /* mutual exclusion for setting startblock */
BlockNumber phs_startblock; /* starting block number */
+ BlockNumber phs_numblock; /* # blocks to scan, or InvalidBlockNumber if
+ * no limit */
pg_atomic_uint64 phs_nallocated; /* number of blocks allocated to
* workers so far. */
} ParallelBlockTableScanDescData;
extern TableScanDesc table_beginscan_parallel(Relation relation,
ParallelTableScanDesc pscan);
+/*
+ * Begin a parallel tid range 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
ParallelBlockTableScanDesc pbscan);
extern void table_block_parallelscan_startblock_init(Relation rel,
ParallelBlockTableScanWorker pbscanwork,
- ParallelBlockTableScanDesc pbscan);
+ ParallelBlockTableScanDesc pbscan,
+ BlockNumber startblock,
+ BlockNumber numblocks);
/* ----------------------------------------------------------------------------
#ifndef NODETIDRANGESCAN_H
#define NODETIDRANGESCAN_H
+#include "access/parallel.h"
#include "nodes/execnodes.h"
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 */
* trss_mintid the lowest TID in the scan range
* trss_maxtid the highest TID in the scan range
* trss_inScan is a scan currently in progress?
+ * trss_pscanlen size of parallel heap scan descriptor
* ----------------
*/
typedef struct TidRangeScanState
ItemPointerData trss_mintid;
ItemPointerData trss_maxtid;
bool trss_inScan;
+ Size trss_pscanlen;
} TidRangeScanState;
/* ----------------
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,
COMMIT;
DROP TABLE tidrangescan;
+-- Tests for parallel TID Range Scans
+BEGIN;
+SET LOCAL parallel_setup_cost TO 0;
+SET LOCAL parallel_tuple_cost TO 0;
+SET LOCAL min_parallel_table_scan_size TO 0;
+SET LOCAL max_parallel_workers_per_gather TO 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)
+
+ROLLBACK;
RESET enable_seqscan;
DROP TABLE tidrangescan;
+-- Tests for parallel TID Range Scans
+BEGIN;
+
+SET LOCAL parallel_setup_cost TO 0;
+SET LOCAL parallel_tuple_cost TO 0;
+SET LOCAL min_parallel_table_scan_size TO 0;
+SET LOCAL max_parallel_workers_per_gather TO 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)';
+
+ROLLBACK;
RESET enable_seqscan;
projects / postgresql.git / commitdiff