From f2b8022f0e4e9fa2af759d6e7ab26301d6688726 Mon Sep 17 00:00:00 2001 From: Bertrand Drouvot Date: Mon, 26 Oct 2026 15:34:27 +0000 Subject: [PATCH v1 3/5] Refactor table scan instrumentation lookup Extract the lookup of leader and per-worker table scan instrumentation from show_scan_io_usage(). This will allow other scan instrumentation to reuse the lookup without coupling it to I/O reporting. Author: Bertrand Drouvot Reviewed-by: Discussion: https://postgr.es/m/ --- src/backend/commands/explain.c | 158 +++++++++++++++++---------------- 1 file changed, 80 insertions(+), 78 deletions(-) 100.0% src/backend/commands/ diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c index 4b1ad4227ac..d0ce72d83ff 100644 --- a/src/backend/commands/explain.c +++ b/src/backend/commands/explain.c @@ -4088,112 +4088,114 @@ print_io_usage(ExplainState *es, IOStats *stats) } /* - * Show information about prefetch and I/O in a scan node. + * Return table scan instrumentation for the leader or a parallel worker. + * + * Pass a negative worker number for the leader. Return NULL if the process + * has no scan instrumentation or the node type does not collect it. */ -static void -show_scan_io_usage(ScanState *planstate, ExplainState *es) +static TableScanInstrumentation * +get_table_scan_instrumentation(ScanState *planstate, int worker) { - Plan *plan = planstate->ps.plan; - IOStats stats = {0}; - - if (!es->io) - return; - - /* - * Initialize counters with stats from the local process first. - * - * The scan descriptor may not exist, e.g. if the scan did not start, or - * because of debug_parallel_query=regress. We still want to collect data - * from workers. - */ - if (planstate->ss_currentScanDesc && - planstate->ss_currentScanDesc->rs_instrument) + if (worker < 0) { - stats = planstate->ss_currentScanDesc->rs_instrument->io; + if (planstate->ss_currentScanDesc) + return planstate->ss_currentScanDesc->rs_instrument; + + return NULL; } - /* - * Accumulate data from parallel workers (if any). - */ - switch (nodeTag(plan)) + switch (nodeTag(planstate->ps.plan)) { case T_BitmapHeapScan: { - SharedBitmapHeapInstrumentation *sinstrument - = ((BitmapHeapScanState *) planstate)->sinstrument; - - if (sinstrument) - { - for (int i = 0; i < sinstrument->num_workers; ++i) - { - BitmapHeapScanInstrumentation *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); - } - } + SharedBitmapHeapInstrumentation *sinstrument = + ((BitmapHeapScanState *) planstate)->sinstrument; + if (sinstrument && worker < sinstrument->num_workers) + return &sinstrument->sinstrument[worker].stats; 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); - } - } + SharedSeqScanInstrumentation *sinstrument = + ((SeqScanState *) planstate)->sinstrument; + if (sinstrument && worker < sinstrument->num_workers) + return &sinstrument->sinstrument[worker].stats; break; } case T_TidRangeScan: { - SharedTidRangeScanInstrumentation *sinstrument - = ((TidRangeScanState *) planstate)->trss_sinstrument; + SharedTidRangeScanInstrumentation *sinstrument = + ((TidRangeScanState *) planstate)->trss_sinstrument; - if (sinstrument) - { - for (int i = 0; i < sinstrument->num_workers; ++i) - { - TidRangeScanInstrumentation *winstrument = &sinstrument->sinstrument[i]; + if (sinstrument && worker < sinstrument->num_workers) + return &sinstrument->sinstrument[worker].stats; + break; + } + default: + break; + } - AccumulateIOStats(&stats, &winstrument->stats.io); + return NULL; +} - if (!es->workers_state) - continue; +/* + * Show information about prefetch and I/O in a scan node. + */ +static void +show_scan_io_usage(ScanState *planstate, ExplainState *es) +{ + TableScanInstrumentation *instrument; + IOStats stats = {0}; - ExplainOpenWorker(i, es); - print_io_usage(es, &winstrument->stats.io); - ExplainCloseWorker(i, es); - } - } + if (!es->io) + return; - break; - } + /* I/O usage is reported only for these scan types */ + switch (nodeTag(planstate->ps.plan)) + { + case T_BitmapHeapScan: + case T_SeqScan: + case T_TidRangeScan: + break; default: /* ignore other plans */ return; } + /* + * Initialize counters with stats from the local process first. + * + * The scan descriptor may not exist, e.g. if the scan did not start, or + * because of debug_parallel_query=regress. We still want to collect data + * from workers. + */ + instrument = get_table_scan_instrumentation(planstate, -1); + if (instrument) + stats = instrument->io; + + /* + * Accumulate data from parallel workers (if any). + */ + for (int i = 0;; ++i) + { + TableScanInstrumentation *winstrument = + get_table_scan_instrumentation(planstate, i); + + if (!winstrument) + break; + + AccumulateIOStats(&stats, &winstrument->io); + + if (!es->workers_state) + continue; + + ExplainOpenWorker(i, es); + print_io_usage(es, &winstrument->io); + ExplainCloseWorker(i, es); + } + print_io_usage(es, &stats); } -- 2.34.1