v19-0002-Logging-for-parallel-autovacuum.patch

From 895131049b2416566781ff585a577bc0342f5f71 Mon Sep 17 00:00:00 2001
From: Daniil Davidov <d.davydov@postgrespro.ru>
Date: Sun, 23 Nov 2025 01:07:47 +0700
Subject: [PATCH v19 2/5] Logging for parallel autovacuum

---
 src/backend/access/heap/vacuumlazy.c  | 27 +++++++++++++++++++++++++--
 src/backend/commands/vacuumparallel.c | 21 +++++++++++++++------
 src/include/commands/vacuum.h         | 16 ++++++++++++++--
 src/tools/pgindent/typedefs.list      |  1 +
 4 files changed, 55 insertions(+), 10 deletions(-)

diff --git a/src/backend/access/heap/vacuumlazy.c b/src/backend/access/heap/vacuumlazy.c
index 1fcb212ab3d..0be33cb84a6 100644
--- a/src/backend/access/heap/vacuumlazy.c
+++ b/src/backend/access/heap/vacuumlazy.c
@@ -347,6 +347,12 @@ typedef struct LVRelState
 	int			num_index_scans;
 	int			num_dead_items_resets;
 	Size		total_dead_items_bytes;
+
+	/*
+	 * Total number of planned and actually launched parallel workers for
+	 * index scans.
+	 */
+	PVWorkersUsage workers_usage;
 	/* Counters that follow are only for scanned_pages */
 	int64		tuples_deleted; /* # deleted from table */
 	int64		tuples_frozen;	/* # newly frozen */
@@ -630,6 +636,7 @@ heap_vacuum_rel(Relation rel, const VacuumParams params,
 	LVRelState *vacrel;
 	bool		verbose,
 				instrument,
+				log_workers_usage = false,	/* for parallel [auto]vacuum only */
 				skipwithvm,
 				frozenxid_updated,
 				minmulti_updated;
@@ -709,6 +716,12 @@ heap_vacuum_rel(Relation rel, const VacuumParams params,
 		indnames = palloc_array(char *, vacrel->nindexes);
 		for (int i = 0; i < vacrel->nindexes; i++)
 			indnames[i] = pstrdup(RelationGetRelationName(vacrel->indrels[i]));
+
+		/*
+		 * Worker usage statistics must be accumulated for parallel autovacuum
+		 * and for VACUUM (PARALLEL, VERBOSE).
+		 */
+		log_workers_usage = (params.nworkers > -1);
 	}
 
 	/*
@@ -781,6 +794,9 @@ heap_vacuum_rel(Relation rel, const VacuumParams params,
 	vacrel->vm_new_visible_frozen_pages = 0;
 	vacrel->vm_new_frozen_pages = 0;
 
+	vacrel->workers_usage.nlaunched = 0;
+	vacrel->workers_usage.nplanned = 0;
+
 	/*
 	 * Get cutoffs that determine which deleted tuples are considered DEAD,
 	 * not just RECENTLY_DEAD, and which XIDs/MXIDs to freeze.  Then determine
@@ -1123,6 +1139,11 @@ heap_vacuum_rel(Relation rel, const VacuumParams params,
 							 orig_rel_pages == 0 ? 100.0 :
 							 100.0 * vacrel->lpdead_item_pages / orig_rel_pages,
 							 vacrel->lpdead_items);
+			if (log_workers_usage)
+				appendStringInfo(&buf,
+								 _("parallel index vacuum/cleanup: %d workers were planned and %d workers were launched in total\n"),
+								 vacrel->workers_usage.nplanned,
+								 vacrel->workers_usage.nlaunched);
 			for (int i = 0; i < vacrel->nindexes; i++)
 			{
 				IndexBulkDeleteResult *istat = vacrel->indstats[i];
@@ -2698,7 +2719,8 @@ lazy_vacuum_all_indexes(LVRelState *vacrel)
 	{
 		/* Outsource everything to parallel variant */
 		parallel_vacuum_bulkdel_all_indexes(vacrel->pvs, old_live_tuples,
-											vacrel->num_index_scans);
+											vacrel->num_index_scans,
+											&vacrel->workers_usage);
 
 		/*
 		 * Do a postcheck to consider applying wraparound failsafe now.  Note
@@ -3131,7 +3153,8 @@ lazy_cleanup_all_indexes(LVRelState *vacrel)
 		/* Outsource everything to parallel variant */
 		parallel_vacuum_cleanup_all_indexes(vacrel->pvs, reltuples,
 											vacrel->num_index_scans,
-											estimated_count);
+											estimated_count,
+											&vacrel->workers_usage);
 	}
 
 	/* Reset the progress counters */
diff --git a/src/backend/commands/vacuumparallel.c b/src/backend/commands/vacuumparallel.c
index cb42d4e572f..c32314f9731 100644
--- a/src/backend/commands/vacuumparallel.c
+++ b/src/backend/commands/vacuumparallel.c
@@ -227,7 +227,7 @@ struct ParallelVacuumState
 static int	parallel_vacuum_compute_workers(Relation *indrels, int nindexes, int nrequested,
 											bool *will_parallel_vacuum);
 static void parallel_vacuum_process_all_indexes(ParallelVacuumState *pvs, int num_index_scans,
-												bool vacuum);
+												bool vacuum, PVWorkersUsage *wusage);
 static void parallel_vacuum_process_safe_indexes(ParallelVacuumState *pvs);
 static void parallel_vacuum_process_unsafe_indexes(ParallelVacuumState *pvs);
 static void parallel_vacuum_process_one_index(ParallelVacuumState *pvs, Relation indrel,
@@ -502,7 +502,7 @@ parallel_vacuum_reset_dead_items(ParallelVacuumState *pvs)
  */
 void
 parallel_vacuum_bulkdel_all_indexes(ParallelVacuumState *pvs, long num_table_tuples,
-									int num_index_scans)
+									int num_index_scans, PVWorkersUsage *wusage)
 {
 	Assert(!IsParallelWorker());
 
@@ -513,7 +513,7 @@ parallel_vacuum_bulkdel_all_indexes(ParallelVacuumState *pvs, long num_table_tup
 	pvs->shared->reltuples = num_table_tuples;
 	pvs->shared->estimated_count = true;
 
-	parallel_vacuum_process_all_indexes(pvs, num_index_scans, true);
+	parallel_vacuum_process_all_indexes(pvs, num_index_scans, true, wusage);
 }
 
 /*
@@ -521,7 +521,8 @@ parallel_vacuum_bulkdel_all_indexes(ParallelVacuumState *pvs, long num_table_tup
  */
 void
 parallel_vacuum_cleanup_all_indexes(ParallelVacuumState *pvs, long num_table_tuples,
-									int num_index_scans, bool estimated_count)
+									int num_index_scans, bool estimated_count,
+									PVWorkersUsage *wusage)
 {
 	Assert(!IsParallelWorker());
 
@@ -533,7 +534,7 @@ parallel_vacuum_cleanup_all_indexes(ParallelVacuumState *pvs, long num_table_tup
 	pvs->shared->reltuples = num_table_tuples;
 	pvs->shared->estimated_count = estimated_count;
 
-	parallel_vacuum_process_all_indexes(pvs, num_index_scans, false);
+	parallel_vacuum_process_all_indexes(pvs, num_index_scans, false, wusage);
 }
 
 /*
@@ -618,7 +619,7 @@ parallel_vacuum_compute_workers(Relation *indrels, int nindexes, int nrequested,
  */
 static void
 parallel_vacuum_process_all_indexes(ParallelVacuumState *pvs, int num_index_scans,
-									bool vacuum)
+									bool vacuum, PVWorkersUsage *wusage)
 {
 	int			nworkers;
 	PVIndVacStatus new_status;
@@ -655,6 +656,10 @@ parallel_vacuum_process_all_indexes(ParallelVacuumState *pvs, int num_index_scan
 	 */
 	nworkers = Min(nworkers, pvs->pcxt->nworkers);
 
+	/* Remember this value, if we asked to */
+	if (wusage != NULL && nworkers > 0)
+		wusage->nplanned += nworkers;
+
 	/*
 	 * Reserve workers in autovacuum global state. Note that we may be given
 	 * fewer workers than we requested.
@@ -725,6 +730,10 @@ parallel_vacuum_process_all_indexes(ParallelVacuumState *pvs, int num_index_scan
 			/* Enable shared cost balance for leader backend */
 			VacuumSharedCostBalance = &(pvs->shared->cost_balance);
 			VacuumActiveNWorkers = &(pvs->shared->active_nworkers);
+
+			/* Remember this value, if we asked to */
+			if (wusage != NULL)
+				wusage->nlaunched += pvs->pcxt->nworkers_launched;
 		}
 
 		if (vacuum)
diff --git a/src/include/commands/vacuum.h b/src/include/commands/vacuum.h
index e885a4b9c77..ec5d70aacdc 100644
--- a/src/include/commands/vacuum.h
+++ b/src/include/commands/vacuum.h
@@ -300,6 +300,16 @@ typedef struct VacDeadItemsInfo
 	int64		num_items;		/* current # of entries */
 } VacDeadItemsInfo;
 
+/*
+ * PVWorkersUsage stores information about total number of launched and planned
+ * workers during parallel vacuum.
+ */
+typedef struct PVWorkersUsage
+{
+	int			nlaunched;
+	int			nplanned;
+} PVWorkersUsage;
+
 /* GUC parameters */
 extern PGDLLIMPORT int default_statistics_target;	/* PGDLLIMPORT for PostGIS */
 extern PGDLLIMPORT int vacuum_freeze_min_age;
@@ -394,11 +404,13 @@ extern TidStore *parallel_vacuum_get_dead_items(ParallelVacuumState *pvs,
 extern void parallel_vacuum_reset_dead_items(ParallelVacuumState *pvs);
 extern void parallel_vacuum_bulkdel_all_indexes(ParallelVacuumState *pvs,
 												long num_table_tuples,
-												int num_index_scans);
+												int num_index_scans,
+												PVWorkersUsage *wusage);
 extern void parallel_vacuum_cleanup_all_indexes(ParallelVacuumState *pvs,
 												long num_table_tuples,
 												int num_index_scans,
-												bool estimated_count);
+												bool estimated_count,
+												PVWorkersUsage *wusage);
 extern void parallel_vacuum_main(dsm_segment *seg, shm_toc *toc);
 
 /* in commands/analyze.c */
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 3f3a888fd0e..afebde72235 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2404,6 +2404,7 @@ PullFilterOps
 PushFilter
 PushFilterOps
 PushFunction
+PVWorkersUsage
 PyCFunction
 PyMethodDef
 PyModuleDef
-- 
2.43.0