From 7f0269e4307f5bb8bd850092aba8a5df8411c587 Mon Sep 17 00:00:00 2001 From: test Date: Tue, 7 Apr 2026 01:38:53 +0200 Subject: [PATCH v13 4/5] Add EXPLAIN (IO) instrumentation for SeqScan Adds support for EXPLAIN (IO) instrumentation for sequential scans. This requires adding shared instrumentation for parallel scans, using the separate DSM approach introduced by dd78e69cfc33. Reviewed-by: Melanie Plageman Reviewed-by: Lukas Fittl Reviewed-by: Andres Freund Discussion: https://postgr.es/m/flat/a177a6dd-240b-455a-8f25-aca0b1c08c6e%40vondra.me --- src/backend/commands/explain.c | 25 +++++ src/backend/executor/execParallel.c | 11 +++ src/backend/executor/nodeSeqscan.c | 127 +++++++++++++++++++++++-- src/include/executor/instrument_node.h | 19 ++++ src/include/executor/nodeSeqscan.h | 9 ++ src/include/nodes/execnodes.h | 1 + src/test/regress/expected/explain.out | 18 +++- src/test/regress/sql/explain.sql | 4 +- src/tools/pgindent/typedefs.list | 2 + 9 files changed, 203 insertions(+), 13 deletions(-) diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c index e9aafdf6e55..18d424da944 100644 --- a/src/backend/commands/explain.c +++ b/src/backend/commands/explain.c @@ -2032,6 +2032,7 @@ ExplainNode(PlanState *planstate, List *ancestors, planstate, es); if (IsA(plan, CteScan)) show_ctescan_info(castNode(CteScanState, planstate), es); + show_scan_io_usage((ScanState *) planstate, es); break; case T_Gather: { @@ -4102,6 +4103,30 @@ show_scan_io_usage(ScanState *planstate, ExplainState *es) } } + break; + } + case T_SeqScan: + { + SharedSeqScanInstrumentation *sinstrument + = ((SeqScanState *) planstate)->sinstrument; + + if (sinstrument) + { + for (int i = 0; i < sinstrument->num_workers; ++i) + { + SeqScanInstrumentation *winstrument = &sinstrument->sinstrument[i]; + + AccumulateIOStats(&stats, &winstrument->stats.io); + + if (!es->workers_state) + continue; + + ExplainOpenWorker(i, es); + print_io_usage(es, &winstrument->stats.io); + ExplainCloseWorker(i, es); + } + } + break; } default: diff --git a/src/backend/executor/execParallel.c b/src/backend/executor/execParallel.c index 1a5ec0c305f..9690f0938ae 100644 --- a/src/backend/executor/execParallel.c +++ b/src/backend/executor/execParallel.c @@ -257,6 +257,9 @@ ExecParallelEstimate(PlanState *planstate, ExecParallelEstimateContext *e) if (planstate->plan->parallel_aware) ExecSeqScanEstimate((SeqScanState *) planstate, e->pcxt); + /* even when not parallel-aware, for EXPLAIN ANALYZE */ + ExecSeqScanInstrumentEstimate((SeqScanState *) planstate, + e->pcxt); break; case T_IndexScanState: if (planstate->plan->parallel_aware) @@ -500,6 +503,9 @@ ExecParallelInitializeDSM(PlanState *planstate, if (planstate->plan->parallel_aware) ExecSeqScanInitializeDSM((SeqScanState *) planstate, d->pcxt); + /* even when not parallel-aware, for EXPLAIN ANALYZE */ + ExecSeqScanInstrumentInitDSM((SeqScanState *) planstate, + d->pcxt); break; case T_IndexScanState: if (planstate->plan->parallel_aware) @@ -1148,6 +1154,9 @@ ExecParallelRetrieveInstrumentation(PlanState *planstate, case T_BitmapHeapScanState: ExecBitmapHeapRetrieveInstrumentation((BitmapHeapScanState *) planstate); break; + case T_SeqScanState: + ExecSeqScanRetrieveInstrumentation((SeqScanState *) planstate); + break; default: break; } @@ -1388,6 +1397,8 @@ ExecParallelInitializeWorker(PlanState *planstate, ParallelWorkerContext *pwcxt) case T_SeqScanState: if (planstate->plan->parallel_aware) ExecSeqScanInitializeWorker((SeqScanState *) planstate, pwcxt); + /* even when not parallel-aware, for EXPLAIN ANALYZE */ + ExecSeqScanInstrumentInitWorker((SeqScanState *) planstate, pwcxt); break; case T_IndexScanState: if (planstate->plan->parallel_aware) diff --git a/src/backend/executor/nodeSeqscan.c b/src/backend/executor/nodeSeqscan.c index 04803b0e37d..a4fcf7c7ad4 100644 --- a/src/backend/executor/nodeSeqscan.c +++ b/src/backend/executor/nodeSeqscan.c @@ -29,6 +29,7 @@ #include "access/relscan.h" #include "access/tableam.h" +#include "executor/execParallel.h" #include "executor/execScan.h" #include "executor/executor.h" #include "executor/nodeSeqscan.h" @@ -65,15 +66,21 @@ SeqNext(SeqScanState *node) if (scandesc == NULL) { + uint32 flags = SO_NONE; + + if (ScanRelIsReadOnly(&node->ss)) + flags |= SO_HINT_REL_READ_ONLY; + + if (estate->es_instrument & INSTRUMENT_IO) + flags |= SO_SCAN_INSTRUMENT; + /* * We reach here if the scan is not parallel, or if we're serially * executing a scan that was planned to be parallel. */ scandesc = table_beginscan(node->ss.ss_currentRelation, estate->es_snapshot, - 0, NULL, - ScanRelIsReadOnly(&node->ss) ? - SO_HINT_REL_READ_ONLY : SO_NONE); + 0, NULL, flags); node->ss.ss_currentScanDesc = scandesc; } @@ -302,6 +309,22 @@ ExecEndSeqScan(SeqScanState *node) */ scanDesc = node->ss.ss_currentScanDesc; + /* + * Collect I/O stats for this process into shared instrumentation. + */ + if (node->sinstrument != NULL && IsParallelWorker()) + { + SeqScanInstrumentation *si; + + Assert(ParallelWorkerNumber < node->sinstrument->num_workers); + si = &node->sinstrument->sinstrument[ParallelWorkerNumber]; + + if (scanDesc && scanDesc->rs_instrument) + { + AccumulateIOStats(&si->stats.io, &scanDesc->rs_instrument->io); + } + } + /* * close heap scan */ @@ -370,6 +393,13 @@ ExecSeqScanInitializeDSM(SeqScanState *node, { EState *estate = node->ss.ps.state; ParallelTableScanDesc pscan; + uint32 flags = SO_NONE; + + if (ScanRelIsReadOnly(&node->ss)) + flags |= SO_HINT_REL_READ_ONLY; + + if (estate->es_instrument & INSTRUMENT_IO) + flags |= SO_SCAN_INSTRUMENT; pscan = shm_toc_allocate(pcxt->toc, node->pscan_len); table_parallelscan_initialize(node->ss.ss_currentRelation, @@ -378,9 +408,7 @@ ExecSeqScanInitializeDSM(SeqScanState *node, shm_toc_insert(pcxt->toc, node->ss.ps.plan->plan_node_id, pscan); node->ss.ss_currentScanDesc = - table_beginscan_parallel(node->ss.ss_currentRelation, pscan, - ScanRelIsReadOnly(&node->ss) ? - SO_HINT_REL_READ_ONLY : SO_NONE); + table_beginscan_parallel(node->ss.ss_currentRelation, pscan, flags); } /* ---------------------------------------------------------------- @@ -410,10 +438,91 @@ ExecSeqScanInitializeWorker(SeqScanState *node, ParallelWorkerContext *pwcxt) { ParallelTableScanDesc pscan; + uint32 flags = SO_NONE; + + if (ScanRelIsReadOnly(&node->ss)) + flags |= SO_HINT_REL_READ_ONLY; + + if (node->ss.ps.state->es_instrument & INSTRUMENT_IO) + flags |= SO_SCAN_INSTRUMENT; pscan = shm_toc_lookup(pwcxt->toc, node->ss.ps.plan->plan_node_id, false); node->ss.ss_currentScanDesc = - table_beginscan_parallel(node->ss.ss_currentRelation, pscan, - ScanRelIsReadOnly(&node->ss) ? - SO_HINT_REL_READ_ONLY : SO_NONE); + table_beginscan_parallel(node->ss.ss_currentRelation, pscan, flags); +} + +/* + * Compute the amount of space we'll need for the shared instrumentation and + * inform pcxt->estimator. + */ +void +ExecSeqScanInstrumentEstimate(SeqScanState *node, ParallelContext *pcxt) +{ + EState *estate = node->ss.ps.state; + + if (!estate->es_instrument || pcxt->nworkers == 0) + return; + + shm_toc_estimate_chunk(&pcxt->estimator, + offsetof(SharedSeqScanInstrumentation, sinstrument) + + sizeof(SeqScanInstrumentation) * pcxt->nworkers); + shm_toc_estimate_keys(&pcxt->estimator, 1); +} + +/* + * Set up parallel sequential scan instrumentation. + */ +void +ExecSeqScanInstrumentInitDSM(SeqScanState *node, ParallelContext *pcxt) +{ + EState *estate = node->ss.ps.state; + SharedSeqScanInstrumentation *sinstrument; + Size size; + + if (!estate->es_instrument || pcxt->nworkers == 0) + return; + + size = offsetof(SharedSeqScanInstrumentation, sinstrument) + + sizeof(SeqScanInstrumentation) * pcxt->nworkers; + sinstrument = shm_toc_allocate(pcxt->toc, size); + memset(sinstrument, 0, size); + sinstrument->num_workers = pcxt->nworkers; + shm_toc_insert(pcxt->toc, + node->ss.ps.plan->plan_node_id + PARALLEL_KEY_SCAN_INSTRUMENT_OFFSET, + sinstrument); + node->sinstrument = sinstrument; +} + +/* + * Look up and save the location of the shared instrumentation. + */ +void +ExecSeqScanInstrumentInitWorker(SeqScanState *node, + ParallelWorkerContext *pwcxt) +{ + if (!node->ss.ps.state->es_instrument) + return; + + node->sinstrument = shm_toc_lookup(pwcxt->toc, + node->ss.ps.plan->plan_node_id + PARALLEL_KEY_SCAN_INSTRUMENT_OFFSET, + true); +} + +/* + * Transfer sequential scan instrumentation from DSM to private memory. + */ +void +ExecSeqScanRetrieveInstrumentation(SeqScanState *node) +{ + SharedSeqScanInstrumentation *sinstrument = node->sinstrument; + Size size; + + if (sinstrument == NULL) + return; + + size = offsetof(SharedSeqScanInstrumentation, sinstrument) + + sinstrument->num_workers * sizeof(SeqScanInstrumentation); + + node->sinstrument = palloc(size); + memcpy(node->sinstrument, sinstrument, size); } diff --git a/src/include/executor/instrument_node.h b/src/include/executor/instrument_node.h index 22a75ccd863..003dc262b5d 100644 --- a/src/include/executor/instrument_node.h +++ b/src/include/executor/instrument_node.h @@ -266,4 +266,23 @@ typedef struct SharedIncrementalSortInfo IncrementalSortInfo sinfo[FLEXIBLE_ARRAY_MEMBER]; } SharedIncrementalSortInfo; + +/* --------------------- + * Instrumentation information for sequential scans + * --------------------- + */ +typedef struct SeqScanInstrumentation +{ + TableScanInstrumentation stats; +} SeqScanInstrumentation; + +/* + * Shared memory container for per-worker information + */ +typedef struct SharedSeqScanInstrumentation +{ + int num_workers; + SeqScanInstrumentation sinstrument[FLEXIBLE_ARRAY_MEMBER]; +} SharedSeqScanInstrumentation; + #endif /* INSTRUMENT_NODE_H */ diff --git a/src/include/executor/nodeSeqscan.h b/src/include/executor/nodeSeqscan.h index 7a1490596fb..9c0ad4879d7 100644 --- a/src/include/executor/nodeSeqscan.h +++ b/src/include/executor/nodeSeqscan.h @@ -28,4 +28,13 @@ extern void ExecSeqScanReInitializeDSM(SeqScanState *node, ParallelContext *pcxt extern void ExecSeqScanInitializeWorker(SeqScanState *node, ParallelWorkerContext *pwcxt); +/* instrument support */ +extern void ExecSeqScanInstrumentEstimate(SeqScanState *node, + ParallelContext *pcxt); +extern void ExecSeqScanInstrumentInitDSM(SeqScanState *node, + ParallelContext *pcxt); +extern void ExecSeqScanInstrumentInitWorker(SeqScanState *node, + ParallelWorkerContext *pwcxt); +extern void ExecSeqScanRetrieveInstrumentation(SeqScanState *node); + #endif /* NODESEQSCAN_H */ diff --git a/src/include/nodes/execnodes.h b/src/include/nodes/execnodes.h index 3ecae7552fc..56febb3204c 100644 --- a/src/include/nodes/execnodes.h +++ b/src/include/nodes/execnodes.h @@ -1670,6 +1670,7 @@ typedef struct SeqScanState { ScanState ss; /* its first field is NodeTag */ Size pscan_len; /* size of parallel heap scan descriptor */ + struct SharedSeqScanInstrumentation *sinstrument; } SeqScanState; /* ---------------- diff --git a/src/test/regress/expected/explain.out b/src/test/regress/expected/explain.out index dc31c7ce9f9..74a4d87801e 100644 --- a/src/test/regress/expected/explain.out +++ b/src/test/regress/expected/explain.out @@ -100,7 +100,7 @@ select explain_filter('explain (buffers, format text) select * from int8_tbl i8' (1 row) \a -select explain_filter('explain (analyze, buffers, format xml) select * from int8_tbl i8'); +select explain_filter('explain (analyze, buffers, io, format xml) select * from int8_tbl i8'); explain_filter @@ -119,6 +119,13 @@ explain_filter N.N N false + N.N + N + N + N + N + N.N + N.N N N N @@ -149,7 +156,7 @@ explain_filter (1 row) -select explain_filter('explain (analyze, serialize, buffers, format yaml) select * from int8_tbl i8'); +select explain_filter('explain (analyze, serialize, buffers, io, format yaml) select * from int8_tbl i8'); explain_filter - Plan: Node Type: "Seq Scan" @@ -166,6 +173,13 @@ explain_filter Actual Rows: N.N Actual Loops: N Disabled: false + Average Prefetch Distance: N.N + Max Prefetch Distance: N + Prefetch Capacity: N + I/O Count: N + I/O Waits: N + Average I/O Size: N.N + Average I/Os In Progress: N.N Shared Hit Blocks: N Shared Read Blocks: N Shared Dirtied Blocks: N diff --git a/src/test/regress/sql/explain.sql b/src/test/regress/sql/explain.sql index 8f10e1aff55..2f163c64bf6 100644 --- a/src/test/regress/sql/explain.sql +++ b/src/test/regress/sql/explain.sql @@ -69,8 +69,8 @@ select explain_filter('explain (analyze, buffers, format text) select * from int select explain_filter('explain (buffers, format text) select * from int8_tbl i8'); \a -select explain_filter('explain (analyze, buffers, format xml) select * from int8_tbl i8'); -select explain_filter('explain (analyze, serialize, buffers, format yaml) select * from int8_tbl i8'); +select explain_filter('explain (analyze, buffers, io, format xml) select * from int8_tbl i8'); +select explain_filter('explain (analyze, serialize, buffers, io, format yaml) select * from int8_tbl i8'); select explain_filter('explain (buffers, format json) select * from int8_tbl i8'); \a diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list index 98b8d78e693..c0436a13ac3 100644 --- a/src/tools/pgindent/typedefs.list +++ b/src/tools/pgindent/typedefs.list @@ -2800,6 +2800,7 @@ SelfJoinCandidate SemTPadded SemiAntiJoinFactors SeqScan +SeqScanInstrumentation SeqScanState SeqTable SeqTableData @@ -2864,6 +2865,7 @@ SharedMemoizeInfo SharedRecordTableEntry SharedRecordTableKey SharedRecordTypmodRegistry +SharedSeqScanInstrumentation SharedSortInfo SharedTuplestore SharedTuplestoreAccessor -- 2.53.0