v6-0001-Add-memory-usage-reporting-to-VACUUM-VERBOSE.patch

From a52aa6adc891141494777ffcd3024f796131e657 Mon Sep 17 00:00:00 2001
From: TatsuyaKawata <kawatatatsuya0913@gmail.com>
Date: Sat, 22 Nov 2025 01:19:33 +0900
Subject: [PATCH v6] Add memory usage reporting to VACUUM VERBOSE

This patch enhances VACUUM VERBOSE to report the memory usage of
dead-items tracking. It shows the total memory consumed across all
resets, the number of times the dead-item storage was reset, and
the configured memory limit.

The counter num_dead_items_resets increases when we collect enough
dead items to trigger index vacuuming. The reporting includes proper
handling of parallel vacuum cases where dead_items_info may be freed.

Reviewed-by: Masahiko Sawada <sawada.mshk@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAHza6qcPitBCkyiKJosDTt3bmxMvzZOTONoebwCkBZrr3rk65Q%40mail.gmail.com
---
 src/backend/access/heap/vacuumlazy.c | 33 ++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
index 65bb0568a86..ef2c72edf5d 100644
--- a/src/backend/access/heap/vacuumlazy.c
+++ b/src/backend/access/heap/vacuumlazy.c
@@ -347,6 +347,8 @@ typedef struct LVRelState
 
 	/* Instrumentation counters */
 	int			num_index_scans;
+	int			num_dead_items_resets;
+	Size		total_dead_items_bytes;
 	/* Counters that follow are only for scanned_pages */
 	int64		tuples_deleted; /* # deleted from table */
 	int64		tuples_frozen;	/* # newly frozen */
@@ -645,6 +647,7 @@ heap_vacuum_rel(Relation rel, const VacuumParams params,
 	BufferUsage startbufferusage = pgBufferUsage;
 	ErrorContextCallback errcallback;
 	char	  **indnames = NULL;
+	Size		dead_items_max_bytes = 0;
 
 	verbose = (params.options & VACOPT_VERBOSE) != 0;
 	instrument = (verbose || (AmAutoVacuumWorkerProcess() &&
@@ -759,6 +762,8 @@ heap_vacuum_rel(Relation rel, const VacuumParams params,
 
 	/* Initialize remaining counters (be tidy) */
 	vacrel->num_index_scans = 0;
+	vacrel->num_dead_items_resets = 0;
+	vacrel->total_dead_items_bytes = 0;
 	vacrel->tuples_deleted = 0;
 	vacrel->tuples_frozen = 0;
 	vacrel->lpdead_items = 0;
@@ -850,6 +855,13 @@ heap_vacuum_rel(Relation rel, const VacuumParams params,
 	 */
 	lazy_scan_heap(vacrel);
 
+	/*
+	 * Save dead items max_bytes before cleanup for reporting the memory usage
+	 * as the dead_items_info is freed in parallel vacuum cases during
+	 * cleanup.
+	 */
+	dead_items_max_bytes = vacrel->dead_items_info->max_bytes;
+
 	/*
 	 * Free resources managed by dead_items_alloc.  This ends parallel mode in
 	 * passing when necessary.
@@ -1154,6 +1166,23 @@ heap_vacuum_rel(Relation rel, const VacuumParams params,
 							 walusage.wal_bytes,
 							 walusage.wal_fpi_bytes,
 							 walusage.wal_buffers_full);
+
+			/*
+			 * Report the dead-items memory usage.
+			 *
+			 * The num_dead_items_resets counter increases when we collect
+			 * enough dead items to trigger index vacuuming, either because
+			 * we've run out of available space or reached the end of the
+			 * table. Note that this counter may be non-zero even when index
+			 * vacuuming is disabled.
+			 */
+			appendStringInfo(&buf,
+							 ngettext("memory usage: %.2f MB in total, with dead-item storage reset %d time (limit was %.2f MB)\n",
+									  "memory usage: %.2f MB in total, with dead-item storage reset %d times (limit was %.2f MB)\n",
+									  vacrel->num_dead_items_resets),
+							 (double) vacrel->total_dead_items_bytes / (1024 * 1024),
+							 vacrel->num_dead_items_resets,
+							 (double) dead_items_max_bytes / (1024 * 1024));
 			appendStringInfo(&buf, _("system usage: %s"), pg_rusage_show(&ru0));
 
 			ereport(verbose ? INFO : LOG,
@@ -3603,6 +3632,10 @@ dead_items_add(LVRelState *vacrel, BlockNumber blkno, OffsetNumber *offsets,
 static void
 dead_items_reset(LVRelState *vacrel)
 {
+	/* Update statistics for dead items */
+	vacrel->num_dead_items_resets++;
+	vacrel->total_dead_items_bytes += TidStoreMemoryUsage(vacrel->dead_items);
+
 	if (ParallelVacuumIsActive(vacrel))
 	{
 		parallel_vacuum_reset_dead_items(vacrel->pvs);
-- 
2.34.1