From 103a54882c40304958b4a360e0ac07f6b70b8fe1 Mon Sep 17 00:00:00 2001
From: Fujii Masao <fujii@postgresql.org>
Date: Fri, 10 Jul 2026 10:54:46 +0900
Subject: [PATCH v1] Restrict pg_stat_io entries for data checksum processes

The data checksums launcher and workers were exposed in pg_stat_io
with the same broad set of object/context combinations as general
background workers. However, many of those entries can never accumulate
I/O statistics for these processes, such as bulkread, bulkwrite,
relation init, and temporary relation entries.

Teach pgstat_tracks_io_object() and pgstat_tracks_io_op() about the
actual I/O performed by the data checksum processes. Keep the entries
needed for catalog scans, worker relation processing with a vacuum
access strategy, and WAL writes and initialization, while excluding WAL
reads and other object/context combinations that can never be used.
---
 src/backend/utils/activity/pgstat_io.c | 31 ++++++++++++++++++++++++++
 src/test/regress/expected/stats.out    | 11 +--------
 2 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/src/backend/utils/activity/pgstat_io.c b/src/backend/utils/activity/pgstat_io.c
index 38bae7b15d2..4f862c961c5 100644
--- a/src/backend/utils/activity/pgstat_io.c
+++ b/src/backend/utils/activity/pgstat_io.c
@@ -464,6 +464,35 @@ pgstat_tracks_io_object(BackendType bktype, IOObject io_object,
 		io_context == IOCONTEXT_BULKWRITE)
 		return false;
 
+	/*
+	 * The data checksums launcher only scans catalogs and emits WAL records
+	 * for checksum state changes.
+	 */
+	if (bktype == B_DATACHECKSUMSWORKER_LAUNCHER)
+	{
+		if (io_object == IOOBJECT_WAL ||
+			(io_object == IOOBJECT_RELATION &&
+			 io_context == IOCONTEXT_NORMAL))
+			return true;
+
+		return false;
+	}
+
+	/*
+	 * The worker also scans catalogs, then processes relations using a vacuum
+	 * access strategy.
+	 */
+	if (bktype == B_DATACHECKSUMSWORKER_WORKER)
+	{
+		if (io_object == IOOBJECT_WAL ||
+			(io_object == IOOBJECT_RELATION &&
+			 (io_context == IOCONTEXT_NORMAL ||
+			  io_context == IOCONTEXT_VACUUM)))
+			return true;
+
+		return false;
+	}
+
 	return true;
 }
 
@@ -507,6 +536,8 @@ pgstat_tracks_io_op(BackendType bktype, IOObject io_object,
 	if (io_object == IOOBJECT_WAL && io_op == IOOP_READ &&
 		(bktype == B_WAL_RECEIVER || bktype == B_BG_WRITER ||
 		 bktype == B_AUTOVAC_LAUNCHER || bktype == B_AUTOVAC_WORKER ||
+		 bktype == B_DATACHECKSUMSWORKER_LAUNCHER ||
+		 bktype == B_DATACHECKSUMSWORKER_WORKER ||
 		 bktype == B_WAL_WRITER))
 		return false;
 
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 03cbc1cdef5..ccb716c7c10 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -51,20 +51,11 @@ client backend|relation|vacuum
 client backend|temp relation|normal
 client backend|wal|init
 client backend|wal|normal
-datachecksums launcher|relation|bulkread
-datachecksums launcher|relation|bulkwrite
-datachecksums launcher|relation|init
 datachecksums launcher|relation|normal
-datachecksums launcher|relation|vacuum
-datachecksums launcher|temp relation|normal
 datachecksums launcher|wal|init
 datachecksums launcher|wal|normal
-datachecksums worker|relation|bulkread
-datachecksums worker|relation|bulkwrite
-datachecksums worker|relation|init
 datachecksums worker|relation|normal
 datachecksums worker|relation|vacuum
-datachecksums worker|temp relation|normal
 datachecksums worker|wal|init
 datachecksums worker|wal|normal
 io worker|relation|bulkread
@@ -111,7 +102,7 @@ walsummarizer|wal|init
 walsummarizer|wal|normal
 walwriter|wal|init
 walwriter|wal|normal
-(95 rows)
+(86 rows)
 \a
 -- List of registered statistics kinds.
 SELECT id, name, fixed_amount,
-- 
2.55.0