Subject: [PATCH v1 5/5] pgstat: move IO statistics to new per-backend infrastructure

From: Bertrand Drouvot <[email-masked]>
Date: Fri, 17 Jul 2026 13:26:07 +0000

PGSTAT_KIND_BACKEND stores each backend's IO statistics in one variable-numbered
entry keyed by ProcNumber. Move IO statistics into a dedicated ProcNumber keyed
dshash associated with the fixed IO statistics kind. The global IO stats hold data
for backends that have exited, while the dshash holds statistics for live backends.

Build pg_stat_io snapshots by copying the global stats and adding every live
per-backend entry.

Transfer the current process's entry into the global stats before deleting it
at process exit or ProcNumber reuse. Transfer all entries before a clean shutdown
writes the statistics file.

Remove IO counters from PGSTAT_KIND_BACKEND and make use of the new infrastructure
in pg_stat_get_backend_io(). This also makes IO statistics available for auxiliary
and shared memory-only workers. Update the documentation to describe the
resulting new behavior.

After WAL, Lock, and IO have moved, PGSTAT_KIND_BACKEND contains no data.
Remove that kind and pgstat_backend.c together with their build entries, shared
and pending structures, callbacks, flags, and call sites.

Author: Bertrand Drouvot <[email-masked]>
Reviewed-by:
Discussion:
---
 doc/src/sgml/monitoring.sgml                 |   9 +-
 src/backend/replication/walsender.c          |   2 -
 src/backend/utils/activity/Makefile          |   1 -
 src/backend/utils/activity/backend_status.c  |   4 -
 src/backend/utils/activity/meson.build       |   1 -
 src/backend/utils/activity/pgstat.c          |  29 +-
 src/backend/utils/activity/pgstat_backend.c  | 332 -------------------
 src/backend/utils/activity/pgstat_io.c       | 225 ++++++++++---
 src/backend/utils/activity/pgstat_relation.c |   2 -
 src/backend/utils/activity/pgstat_shmem.c    |   9 +-
 src/backend/utils/activity/pgstat_wal.c      |   1 -
 src/backend/utils/adt/pgstatfuncs.c          |  47 +--
 src/include/pgstat.h                         |  53 +--
 src/include/utils/pgstat_internal.h          |  41 +--
 src/include/utils/pgstat_kind.h              |  15 +-
 src/test/regress/expected/stats.out          |  40 ++-
 src/test/regress/sql/stats.sql               |  11 +-
 src/tools/pgindent/typedefs.list             |   5 +-
 18 files changed, 282 insertions(+), 545 deletions(-)
  70.6% src/backend/utils/activity/
   6.0% src/backend/utils/adt/
   6.3% src/include/utils/
   5.5% src/include/
   6.1% src/test/regress/expected/
   3.2% src/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index d3618e0b920..e83a68b686e 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5797,12 +5797,6 @@ description | Waiting for a newly initialized WAL file to reach durable storage
         Returns I/O statistics about the backend with the specified
         process ID. The output fields are exactly the same as the ones in the
         <structname>pg_stat_io</structname> view.
-       </para>
-       <para>
-        The function does not return I/O statistics for the checkpointer,
-        the background writer, the startup process and the autovacuum launcher
-        as they are already visible in the <structname>pg_stat_io</structname>
-        view and there is only one of each.
        </para></entry>
       </row>
 
@@ -5964,7 +5958,8 @@ description | Waiting for a newly initialized WAL file to reach durable storage
         <listitem>
          <para>
           <literal>io</literal>: Reset all the counters shown in the
-          <structname>pg_stat_io</structname> view.
+          <structname>pg_stat_io</structname> view, as well as per-backend
+          I/O statistics returned by <function>pg_stat_get_backend_io</function>.
          </para>
         </listitem>
         <listitem>
diff --git a/src/backend/replication/walsender.c b/src/backend/replication/walsender.c
index c65dd324325..6d4c15cad4c 100644
--- a/src/backend/replication/walsender.c
+++ b/src/backend/replication/walsender.c
@@ -2083,7 +2083,6 @@ WalSndWaitForWal(XLogRecPtr loc)
 									   WALSENDER_STATS_FLUSH_INTERVAL))
 		{
 			pgstat_flush_io(false);
-			(void) pgstat_flush_backend(false, PGSTAT_BACKEND_FLUSH_IO);
 			last_flush = now;
 		}
 
@@ -3177,7 +3176,6 @@ WalSndLoop(WalSndSendDataCallback send_data)
 										   WALSENDER_STATS_FLUSH_INTERVAL))
 			{
 				pgstat_flush_io(false);
-				(void) pgstat_flush_backend(false, PGSTAT_BACKEND_FLUSH_IO);
 				last_flush = now;
 			}
 
diff --git a/src/backend/utils/activity/Makefile b/src/backend/utils/activity/Makefile
index 5fed953c28a..015e6e05978 100644
--- a/src/backend/utils/activity/Makefile
+++ b/src/backend/utils/activity/Makefile
@@ -20,7 +20,6 @@ OBJS = \
 	backend_status.o \
 	pgstat.o \
 	pgstat_archiver.o \
-	pgstat_backend.o \
 	pgstat_bgwriter.o \
 	pgstat_checkpointer.o \
 	pgstat_database.o \
diff --git a/src/backend/utils/activity/backend_status.c b/src/backend/utils/activity/backend_status.c
index d685fc5cd87..7088fc09651 100644
--- a/src/backend/utils/activity/backend_status.c
+++ b/src/backend/utils/activity/backend_status.c
@@ -458,10 +458,6 @@ pgstat_bestart_final(void)
 
 	PGSTAT_END_WRITE_ACTIVITY(beentry);
 
-	/* Create the backend statistics entry */
-	if (pgstat_tracks_backend_bktype(MyBackendType))
-		pgstat_create_backend(MyProcNumber);
-
 	/* Update app name to current GUC setting */
 	if (application_name)
 		pgstat_report_appname(application_name);
diff --git a/src/backend/utils/activity/meson.build b/src/backend/utils/activity/meson.build
index 470b5dac402..afbc5a625ea 100644
--- a/src/backend/utils/activity/meson.build
+++ b/src/backend/utils/activity/meson.build
@@ -5,7 +5,6 @@ backend_sources += files(
   'backend_status.c',
   'pgstat.c',
   'pgstat_archiver.c',
-  'pgstat_backend.c',
   'pgstat_bgwriter.c',
   'pgstat_checkpointer.c',
   'pgstat_database.c',
diff --git a/src/backend/utils/activity/pgstat.c b/src/backend/utils/activity/pgstat.c
index 2234bdb6857..6af5f2ce6ab 100644
--- a/src/backend/utils/activity/pgstat.c
+++ b/src/backend/utils/activity/pgstat.c
@@ -77,7 +77,6 @@
  *
  * Each statistics kind is handled in a dedicated file:
  * - pgstat_archiver.c
- * - pgstat_backend.c
  * - pgstat_bgwriter.c
  * - pgstat_checkpointer.c
  * - pgstat_database.c
@@ -402,22 +401,6 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
 		.reset_timestamp_cb = pgstat_subscription_reset_timestamp_cb,
 	},
 
-	[PGSTAT_KIND_BACKEND] = {
-		.name = "backend",
-
-		.fixed_amount = false,
-		.write_to_file = false,
-
-		.accessed_across_databases = true,
-
-		.shared_size = sizeof(PgStatShared_Backend),
-		.shared_data_off = offsetof(PgStatShared_Backend, stats),
-		.shared_data_len = sizeof(((PgStatShared_Backend *) 0)->stats),
-
-		.flush_static_cb = pgstat_backend_flush_cb,
-		.reset_timestamp_cb = pgstat_backend_reset_timestamp_cb,
-	},
-
 	/* stats for fixed-numbered (mostly 1) objects */
 
 	[PGSTAT_KIND_ARCHIVER] = {
@@ -483,6 +466,11 @@ static const PgStat_KindInfo pgstat_kind_builtin_infos[PGSTAT_KIND_BUILTIN_SIZE]
 		.init_shmem_cb = pgstat_io_init_shmem_cb,
 		.reset_all_cb = pgstat_io_reset_all_cb,
 		.snapshot_cb = pgstat_io_snapshot_cb,
+
+		.per_backend_data_off = offsetof(PgStatShared_IOBackendEntry, stats),
+		.per_backend_data_len = sizeof(PgStat_BackendIO),
+		.per_backend_hash_handle_off = offsetof(PgStatShared_IO, backend_hash_handle),
+		.per_backend_acc_cb = pgstat_io_per_backend_acc_cb,
 	},
 
 	[PGSTAT_KIND_LOCK] = {
@@ -659,6 +647,7 @@ pgstat_before_server_shutdown(int code, Datum arg)
 		/* Transfer all live per-backend stats before writing the stats file. */
 		pgstat_wal_acc_all_backends();
 		pgstat_lock_acc_all_backends();
+		pgstat_io_acc_all_backends();
 
 		pgStatLocal.shmem->is_shutdown = true;
 		pgstat_write_statsfile();
@@ -699,13 +688,10 @@ pgstat_shutdown_hook(int code, Datum arg)
 	Assert(dlist_is_empty(&pgStatPending));
 	dlist_init(&pgStatPending);
 
-	/* drop the backend stats entry */
-	if (!pgstat_drop_entry(PGSTAT_KIND_BACKEND, InvalidOid, MyProcNumber, false))
-		pgstat_request_entry_refs_gc();
-
 	/* Accumulate per-backend stats into the global stats */
 	pgstat_wal_acc_backend_cb();
 	pgstat_lock_acc_backend_cb();
+	pgstat_io_acc_backend_cb();
 
 	pgstat_detach_shmem();
 
@@ -734,6 +720,7 @@ pgstat_initialize(void)
 	 */
 	pgstat_wal_acc_backend_cb();
 	pgstat_lock_acc_backend_cb();
+	pgstat_io_acc_backend_cb();
 
 	/*
 	 * Create and cache per-backend statistics entries here. This also covers
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
deleted file mode 100644
index 8dda2cd88c1..00000000000
--- a/src/backend/utils/activity/pgstat_backend.c
+++ /dev/null
@@ -1,332 +0,0 @@
-/* -------------------------------------------------------------------------
- *
- * pgstat_backend.c
- *	  Implementation of backend statistics.
- *
- * This file contains the implementation of backend statistics.  It is kept
- * separate from pgstat.c to enforce the line between the statistics access /
- * storage implementation and the details about individual types of
- * statistics.
- *
- * This statistics kind uses a proc number as object ID for the hash table
- * of pgstats.  Entries are created each time a process is spawned, and are
- * dropped when the process exits.  These are not written to the pgstats file
- * on disk.  Pending statistics are managed without direct interactions with
- * PgStat_EntryRef->pending, relying on PendingBackendStats instead so as it
- * is possible to report data within critical sections.
- *
- * Copyright (c) 2001-2026, PostgreSQL Global Development Group
- *
- * IDENTIFICATION
- *	  src/backend/utils/activity/pgstat_backend.c
- * -------------------------------------------------------------------------
- */
-
-#include "postgres.h"
-
-#include "access/xlog.h"
-#include "executor/instrument.h"
-#include "storage/bufmgr.h"
-#include "storage/proc.h"
-#include "storage/procarray.h"
-#include "utils/memutils.h"
-#include "utils/pgstat_internal.h"
-
-/*
- * Backend statistics counts waiting to be flushed out. These counters may be
- * reported within critical sections so we use static memory in order to avoid
- * memory allocation.
- */
-static PgStat_BackendPending PendingBackendStats;
-static bool backend_has_iostats = false;
-
-/*
- * Utility routines to report I/O stats for backends, kept here to avoid
- * exposing PendingBackendStats to the outside world.
- */
-void
-pgstat_count_backend_io_op_time(IOObject io_object, IOContext io_context,
-								IOOp io_op, instr_time io_time)
-{
-	Assert(track_io_timing || track_wal_io_timing);
-
-	if (!pgstat_tracks_backend_bktype(MyBackendType))
-		return;
-
-	Assert(pgstat_tracks_io_op(MyBackendType, io_object, io_context, io_op));
-
-	INSTR_TIME_ADD(PendingBackendStats.pending_io.pending_times[io_object][io_context][io_op],
-				   io_time);
-
-	backend_has_iostats = true;
-	pgstat_report_fixed = true;
-}
-
-void
-pgstat_count_backend_io_op(IOObject io_object, IOContext io_context,
-						   IOOp io_op, uint32 cnt, uint64 bytes)
-{
-	if (!pgstat_tracks_backend_bktype(MyBackendType))
-		return;
-
-	Assert(pgstat_tracks_io_op(MyBackendType, io_object, io_context, io_op));
-
-	PendingBackendStats.pending_io.counts[io_object][io_context][io_op] += cnt;
-	PendingBackendStats.pending_io.bytes[io_object][io_context][io_op] += bytes;
-
-	backend_has_iostats = true;
-	pgstat_report_fixed = true;
-}
-
-/*
- * Returns statistics of a backend by proc number.
- */
-PgStat_Backend *
-pgstat_fetch_stat_backend(ProcNumber procNumber)
-{
-	PgStat_Backend *backend_entry;
-
-	backend_entry = (PgStat_Backend *) pgstat_fetch_entry(PGSTAT_KIND_BACKEND,
-														  InvalidOid, procNumber,
-														  NULL);
-
-	return backend_entry;
-}
-
-/*
- * Returns statistics of a backend by pid.
- *
- * This routine includes sanity checks to ensure that the backend exists and
- * is running.  "bktype" can be optionally defined to return the BackendType
- * of the backend whose statistics are returned.
- */
-PgStat_Backend *
-pgstat_fetch_stat_backend_by_pid(int pid, BackendType *bktype)
-{
-	PGPROC	   *proc;
-	PgBackendStatus *beentry;
-	ProcNumber	procNumber;
-	PgStat_Backend *backend_stats;
-
-	proc = BackendPidGetProc(pid);
-	if (bktype)
-		*bktype = B_INVALID;
-
-	/* this could be an auxiliary process */
-	if (!proc)
-		proc = AuxiliaryPidGetProc(pid);
-
-	if (!proc)
-		return NULL;
-
-	procNumber = GetNumberFromPGProc(proc);
-
-	beentry = pgstat_get_beentry_by_proc_number(procNumber);
-	if (!beentry)
-		return NULL;
-
-	/* check if the backend type tracks statistics */
-	if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
-		return NULL;
-
-	/* if PID does not match, leave */
-	if (beentry->st_procpid != pid)
-		return NULL;
-
-	if (bktype)
-		*bktype = beentry->st_backendType;
-
-	/*
-	 * Retrieve the entry.  Note that "beentry" may be freed depending on the
-	 * value of stats_fetch_consistency, so do not access it from this point.
-	 */
-	backend_stats = pgstat_fetch_stat_backend(procNumber);
-	if (!backend_stats)
-	{
-		if (bktype)
-			*bktype = B_INVALID;
-		return NULL;
-	}
-
-	return backend_stats;
-}
-
-/*
- * Flush out locally pending backend IO statistics.  Locking is managed
- * by the caller.
- */
-static void
-pgstat_flush_backend_entry_io(PgStat_EntryRef *entry_ref)
-{
-	PgStatShared_Backend *shbackendent;
-	PgStat_BktypeIO *bktype_shstats;
-	PgStat_PendingIO pending_io;
-
-	/*
-	 * This function can be called even if nothing at all has happened for IO
-	 * statistics.  In this case, avoid unnecessarily modifying the stats
-	 * entry.
-	 */
-	if (!backend_has_iostats)
-		return;
-
-	shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
-	bktype_shstats = &shbackendent->stats.io_stats;
-	pending_io = PendingBackendStats.pending_io;
-
-	for (int io_object = 0; io_object < IOOBJECT_NUM_TYPES; io_object++)
-	{
-		for (int io_context = 0; io_context < IOCONTEXT_NUM_TYPES; io_context++)
-		{
-			for (int io_op = 0; io_op < IOOP_NUM_TYPES; io_op++)
-			{
-				instr_time	time;
-
-				bktype_shstats->counts[io_object][io_context][io_op] +=
-					pending_io.counts[io_object][io_context][io_op];
-				bktype_shstats->bytes[io_object][io_context][io_op] +=
-					pending_io.bytes[io_object][io_context][io_op];
-				time = pending_io.pending_times[io_object][io_context][io_op];
-
-				bktype_shstats->times[io_object][io_context][io_op] +=
-					INSTR_TIME_GET_MICROSEC(time);
-			}
-		}
-	}
-
-	/*
-	 * Clear out the statistics buffer, so it can be re-used.
-	 */
-	MemSet(&PendingBackendStats.pending_io, 0, sizeof(PgStat_PendingIO));
-
-	backend_has_iostats = false;
-}
-
-/*
- * Flush out locally pending backend statistics
- *
- * "flags" parameter controls which statistics to flush.  Returns true
- * if some statistics could not be flushed due to lock contention.
- */
-bool
-pgstat_flush_backend(bool nowait, uint32 flags)
-{
-	PgStat_EntryRef *entry_ref;
-	bool		has_pending_data = false;
-
-	if (!pgstat_tracks_backend_bktype(MyBackendType))
-		return false;
-
-	/* Some IO data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_IO) && backend_has_iostats)
-		has_pending_data = true;
-
-	if (!has_pending_data)
-		return false;
-
-	entry_ref = pgstat_get_entry_ref_locked(PGSTAT_KIND_BACKEND, InvalidOid,
-											MyProcNumber, nowait);
-	if (!entry_ref)
-		return true;
-
-	/* Flush requested statistics */
-	if (flags & PGSTAT_BACKEND_FLUSH_IO)
-		pgstat_flush_backend_entry_io(entry_ref);
-
-	pgstat_unlock_entry(entry_ref);
-
-	return false;
-}
-
-/*
- * Callback to flush out locally pending backend statistics.
- *
- * If some stats could not be flushed due to lock contention, return true.
- */
-bool
-pgstat_backend_flush_cb(bool nowait)
-{
-	return pgstat_flush_backend(nowait, PGSTAT_BACKEND_FLUSH_ALL);
-}
-
-/*
- * Create backend statistics entry for proc number.
- */
-void
-pgstat_create_backend(ProcNumber procnum)
-{
-	PgStat_EntryRef *entry_ref;
-	PgStatShared_Backend *shstatent;
-
-	entry_ref = pgstat_get_entry_ref_locked(PGSTAT_KIND_BACKEND, InvalidOid,
-											procnum, false);
-	shstatent = (PgStatShared_Backend *) entry_ref->shared_stats;
-
-	/*
-	 * NB: need to accept that there might be stats from an older backend,
-	 * e.g. if we previously used this proc number.
-	 */
-	memset(&shstatent->stats, 0, sizeof(shstatent->stats));
-	pgstat_unlock_entry(entry_ref);
-
-	MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
-	backend_has_iostats = false;
-}
-
-/*
- * Backend statistics are not collected for all BackendTypes.
- *
- * The following BackendTypes do not participate in the backend stats
- * subsystem:
- * - The same and for the same reasons as in pgstat_tracks_io_bktype().
- * - B_BG_WRITER, B_CHECKPOINTER, B_STARTUP and B_AUTOVAC_LAUNCHER because their
- * I/O stats are already visible in pg_stat_io and there is only one of those.
- *
- * Function returns true if BackendType participates in the backend stats
- * subsystem and false if it does not.
- *
- * When adding a new BackendType, also consider adding relevant restrictions to
- * pgstat_tracks_io_object() and pgstat_tracks_io_op().
- */
-bool
-pgstat_tracks_backend_bktype(BackendType bktype)
-{
-	/*
-	 * List every type so that new backend types trigger a warning about
-	 * needing to adjust this switch.
-	 */
-	switch (bktype)
-	{
-		case B_INVALID:
-		case B_AUTOVAC_LAUNCHER:
-		case B_DEAD_END_BACKEND:
-		case B_ARCHIVER:
-		case B_LOGGER:
-		case B_BG_WRITER:
-		case B_CHECKPOINTER:
-		case B_IO_WORKER:
-		case B_STARTUP:
-		case B_DATACHECKSUMSWORKER_LAUNCHER:
-		case B_DATACHECKSUMSWORKER_WORKER:
-			return false;
-
-		case B_AUTOVAC_WORKER:
-		case B_BACKEND:
-		case B_BG_WORKER:
-		case B_STANDALONE_BACKEND:
-		case B_SLOTSYNC_WORKER:
-		case B_WAL_RECEIVER:
-		case B_WAL_SENDER:
-		case B_WAL_SUMMARIZER:
-		case B_WAL_WRITER:
-			return true;
-	}
-
-	return false;
-}
-
-void
-pgstat_backend_reset_timestamp_cb(PgStatShared_Common *header, TimestampTz ts)
-{
-	((PgStatShared_Backend *) header)->stats.stat_reset_timestamp = ts;
-}
diff --git a/src/backend/utils/activity/pgstat_io.c b/src/backend/utils/activity/pgstat_io.c
index 8ec1aad5078..5e65bc5cb4b 100644
--- a/src/backend/utils/activity/pgstat_io.c
+++ b/src/backend/utils/activity/pgstat_io.c
@@ -7,6 +7,11 @@
  * from pgstat.c to enforce the line between the statistics access / storage
  * implementation and the details about individual types of statistics.
  *
+ * IO statistics use a per-backend dshash to avoid double-counting. Each
+ * process flushes IO stats to its own entry in the dshash (keyed by
+ * ProcNumber). The global pg_stat_io view aggregates the global stats
+ * (which holds stats from exited processes) plus all live per-backend entries.
+ *
  * Copyright (c) 2021-2026, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
@@ -68,9 +73,6 @@ pgstat_count_io_op(IOObject io_object, IOContext io_context, IOOp io_op,
 	PendingIOStats.counts[io_object][io_context][io_op] += cnt;
 	PendingIOStats.bytes[io_object][io_context][io_op] += bytes;
 
-	/* Add the per-backend counts */
-	pgstat_count_backend_io_op(io_object, io_context, io_op, cnt, bytes);
-
 	have_iostats = true;
 	pgstat_report_fixed = true;
 }
@@ -143,10 +145,6 @@ pgstat_count_io_op_time(IOObject io_object, IOContext io_context, IOOp io_op,
 
 		INSTR_TIME_ADD(PendingIOStats.pending_times[io_object][io_context][io_op],
 					   io_time);
-
-		/* Add the per-backend count */
-		pgstat_count_backend_io_op_time(io_object, io_context, io_op,
-										io_time);
 	}
 
 	pgstat_count_io_op(io_object, io_context, io_op, cnt, bytes);
@@ -170,7 +168,7 @@ pgstat_flush_io(bool nowait)
 }
 
 /*
- * Flush out locally pending IO statistics
+ * Flush out locally pending IO statistics to the per-backend dshash entry.
  *
  * If no stats have been recorded, this function returns false.
  *
@@ -180,20 +178,18 @@ pgstat_flush_io(bool nowait)
 bool
 pgstat_io_flush_cb(bool nowait)
 {
-	LWLock	   *bktype_lock;
+	PgStatShared_IOBackendEntry *entry;
 	PgStat_BktypeIO *bktype_shstats;
 
 	if (!have_iostats)
 		return false;
 
-	bktype_lock = &pgStatLocal.shmem->io.locks[MyBackendType];
-	bktype_shstats =
-		&pgStatLocal.shmem->io.stats.stats[MyBackendType];
+	entry = pgstat_lock_my_per_backend_entry(PGSTAT_KIND_IO, nowait);
 
-	if (!nowait)
-		LWLockAcquire(bktype_lock, LW_EXCLUSIVE);
-	else if (!LWLockConditionalAcquire(bktype_lock, LW_EXCLUSIVE))
-		return true;
+	if (entry == NULL)
+		return nowait;
+
+	bktype_shstats = &entry->stats.stats;
 
 	for (int io_object = 0; io_object < IOOBJECT_NUM_TYPES; io_object++)
 	{
@@ -217,12 +213,9 @@ pgstat_io_flush_cb(bool nowait)
 		}
 	}
 
-	Assert(pgstat_bktype_io_stats_valid(bktype_shstats, MyBackendType));
-
-	LWLockRelease(bktype_lock);
+	LWLockRelease(&entry->header.lock);
 
 	memset(&PendingIOStats, 0, sizeof(PendingIOStats));
-
 	have_iostats = false;
 
 	return false;
@@ -271,55 +264,70 @@ pgstat_io_init_shmem_cb(void *stats)
 {
 	PgStatShared_IO *stat_shmem = (PgStatShared_IO *) stats;
 
-	for (int i = 0; i < BACKEND_NUM_TYPES; i++)
-		LWLockInitialize(&stat_shmem->locks[i], LWTRANCHE_PGSTATS_DATA);
+	LWLockInitialize(&stat_shmem->lock, LWTRANCHE_PGSTATS_DATA);
 }
 
 void
 pgstat_io_reset_all_cb(TimestampTz ts)
 {
-	for (int i = 0; i < BACKEND_NUM_TYPES; i++)
-	{
-		LWLock	   *bktype_lock = &pgStatLocal.shmem->io.locks[i];
-		PgStat_BktypeIO *bktype_shstats = &pgStatLocal.shmem->io.stats.stats[i];
+	PgStatShared_IO *shmem = &pgStatLocal.shmem->io;
+	dshash_seq_status hstat;
+	PgStatShared_IOBackendEntry *entry;
+	dshash_table *hash;
 
-		LWLockAcquire(bktype_lock, LW_EXCLUSIVE);
+	hash = pgstat_per_backend_attach(PGSTAT_KIND_IO);
 
-		/*
-		 * Use the lock in the first BackendType's PgStat_BktypeIO to protect
-		 * the reset timestamp as well.
-		 */
-		if (i == 0)
-			pgStatLocal.shmem->io.stats.stat_reset_timestamp = ts;
+	/*
+	 * Hold the kind lock while resetting both the global stats and live
+	 * entries. Transfers hold the same lock, so pre-reset counters cannot be
+	 * moved into the global stats after it is reset.
+	 */
+	LWLockAcquire(&shmem->lock, LW_EXCLUSIVE);
+	memset(&shmem->stats, 0, sizeof(shmem->stats));
+	shmem->stats.stat_reset_timestamp = ts;
 
-		memset(bktype_shstats, 0, sizeof(*bktype_shstats));
-		LWLockRelease(bktype_lock);
+	/* Reset all per-backend entries */
+	if (hash != NULL)
+	{
+		dshash_seq_init(&hstat, hash, true);
+		while ((entry = dshash_seq_next(&hstat)) != NULL)
+		{
+			LWLockAcquire(&entry->header.lock, LW_EXCLUSIVE);
+			memset(&entry->stats.stats, 0, sizeof(PgStat_BktypeIO));
+			entry->stats.stat_reset_timestamp = ts;
+			LWLockRelease(&entry->header.lock);
+		}
+		dshash_seq_term(&hstat);
 	}
+
+	LWLockRelease(&shmem->lock);
 }
 
+/*
+ * Build IO stats snapshot by aggregating global stats and all live
+ * per-backend entries.
+ */
 void
 pgstat_io_snapshot_cb(void)
 {
-	for (int i = 0; i < BACKEND_NUM_TYPES; i++)
-	{
-		LWLock	   *bktype_lock = &pgStatLocal.shmem->io.locks[i];
-		PgStat_BktypeIO *bktype_shstats = &pgStatLocal.shmem->io.stats.stats[i];
-		PgStat_BktypeIO *bktype_snap = &pgStatLocal.snapshot.io.stats[i];
+	PgStatShared_IO *shmem = &pgStatLocal.shmem->io;
+	PgStat_IO  *snap = &pgStatLocal.snapshot.io;
+	dshash_table *hash;
 
-		LWLockAcquire(bktype_lock, LW_SHARED);
+	hash = pgstat_per_backend_attach(PGSTAT_KIND_IO);
 
-		/*
-		 * Use the lock in the first BackendType's PgStat_BktypeIO to protect
-		 * the reset timestamp as well.
-		 */
-		if (i == 0)
-			pgStatLocal.snapshot.io.stat_reset_timestamp =
-				pgStatLocal.shmem->io.stats.stat_reset_timestamp;
+	/*
+	 * Prevent entries from moving to the global stats between copying it and
+	 * scanning the per-backend hash.
+	 */
+	LWLockAcquire(&shmem->lock, LW_SHARED);
+	memcpy(snap, &shmem->stats, sizeof(PgStat_IO));
 
-		/* using struct assignment due to better type safety */
-		*bktype_snap = *bktype_shstats;
-		LWLockRelease(bktype_lock);
-	}
+	/* Add in all live per-backend entries */
+	if (hash != NULL)
+		pgstat_per_backend_snapshot(PGSTAT_KIND_IO, hash, snap);
+
+	LWLockRelease(&shmem->lock);
 }
 
 /*
@@ -581,3 +589,116 @@ pgstat_tracks_io_op(BackendType bktype, IOObject io_object,
 
 	return true;
 }
+
+/*
+ * Accumulate IO counters from src into dst.
+ */
+static inline void
+pgstat_io_accumulate_counters(PgStat_BktypeIO *dst, const PgStat_BktypeIO *src)
+{
+	for (int io_object = 0; io_object < IOOBJECT_NUM_TYPES; io_object++)
+	{
+		for (int io_context = 0; io_context < IOCONTEXT_NUM_TYPES; io_context++)
+		{
+			for (int io_op = 0; io_op < IOOP_NUM_TYPES; io_op++)
+			{
+				dst->counts[io_object][io_context][io_op] +=
+					src->counts[io_object][io_context][io_op];
+				dst->bytes[io_object][io_context][io_op] +=
+					src->bytes[io_object][io_context][io_op];
+				dst->times[io_object][io_context][io_op] +=
+					src->times[io_object][io_context][io_op];
+			}
+		}
+	}
+}
+
+/*
+ * Accumulate one per-backend IO entry into a snapshot or the global stats.
+ */
+void
+pgstat_io_per_backend_acc_cb(void *dst, void *entry)
+{
+	PgStat_IO  *stats = dst;
+	PgStatShared_IOBackendEntry *e = (PgStatShared_IOBackendEntry *) entry;
+	BackendType bktype = e->header.backend_type;
+
+	if (bktype == B_INVALID)
+		return;
+
+	pgstat_io_accumulate_counters(&stats->stats[bktype], &e->stats.stats);
+}
+
+/*
+ * Accumulate a backend's IO stats into the global stats, then remove the
+ * entry from the dshash.
+ *
+ * Called at backend exit after the final flush, or when a ProcNumber is
+ * being reused.
+ */
+void
+pgstat_io_acc_backend_cb(void)
+{
+	pgstat_acc_my_per_backend(PGSTAT_KIND_IO, &pgStatLocal.shmem->io.lock);
+}
+
+/*
+ * Accumulate all remaining per-backend IO stats entries into the global stats
+ * and remove them. Called at clean server shutdown to ensure all flushed data
+ * is preserved in the stats file.
+ */
+void
+pgstat_io_acc_all_backends(void)
+{
+	pgstat_acc_all_per_backend(PGSTAT_KIND_IO, &pgStatLocal.shmem->io.lock);
+}
+
+/*
+ * Returns per-backend IO statistics for the given ProcNumber.
+ */
+PgStat_BackendIO *
+pgstat_fetch_stat_backend_io(ProcNumber procnum)
+{
+	return (PgStat_BackendIO *) pgstat_fetch_per_backend(PGSTAT_KIND_IO, procnum);
+}
+
+/*
+ * Reset a backend's IO stats. Accumulate the entry's counters into the
+ * global stats, then zero the stats and set the reset timestamp.
+ */
+void
+pgstat_io_reset_backend_cb(ProcNumber procnum, TimestampTz ts)
+{
+	PgStatShared_IO *shmem = &pgStatLocal.shmem->io;
+	dshash_table *hash;
+	PgStatShared_IOBackendEntry *entry;
+
+	hash = pgstat_per_backend_attach(PGSTAT_KIND_IO);
+
+	if (hash == NULL)
+		return;
+
+	LWLockAcquire(&shmem->lock, LW_EXCLUSIVE);
+
+	entry = dshash_find(hash, &procnum, true);
+
+	if (entry == NULL)
+	{
+		LWLockRelease(&shmem->lock);
+		return;
+	}
+
+	LWLockAcquire(&entry->header.lock, LW_EXCLUSIVE);
+
+	/* Accumulate current stats into global before zeroing */
+	pgstat_io_accumulate_counters(&shmem->stats.stats[entry->header.backend_type],
+								  &entry->stats.stats);
+
+	/* Zero stats and set reset timestamp */
+	memset(&entry->stats, 0, sizeof(entry->stats));
+	entry->stats.stat_reset_timestamp = ts;
+
+	LWLockRelease(&entry->header.lock);
+	dshash_release_lock(hash, entry);
+	LWLockRelease(&shmem->lock);
+}
diff --git a/src/backend/utils/activity/pgstat_relation.c b/src/backend/utils/activity/pgstat_relation.c
index 04f2eb21d0b..8080bc1cbba 100644
--- a/src/backend/utils/activity/pgstat_relation.c
+++ b/src/backend/utils/activity/pgstat_relation.c
@@ -269,7 +269,6 @@ pgstat_report_vacuum(Relation rel, PgStat_Counter livetuples,
 	 * VACUUM command has processed all tables and committed.
 	 */
 	pgstat_flush_io(false);
-	(void) pgstat_flush_backend(false, PGSTAT_BACKEND_FLUSH_IO);
 }
 
 /*
@@ -364,7 +363,6 @@ pgstat_report_analyze(Relation rel,
 
 	/* see pgstat_report_vacuum() */
 	pgstat_flush_io(false);
-	(void) pgstat_flush_backend(false, PGSTAT_BACKEND_FLUSH_IO);
 }
 
 /*
diff --git a/src/backend/utils/activity/pgstat_shmem.c b/src/backend/utils/activity/pgstat_shmem.c
index 3b003f00245..7730dd95766 100644
--- a/src/backend/utils/activity/pgstat_shmem.c
+++ b/src/backend/utils/activity/pgstat_shmem.c
@@ -118,12 +118,11 @@ pgstat_dsa_init_size(void)
 	/*
 	 * The dshash header / initial buckets array needs to fit into "plain"
 	 * shared memory, but it's beneficial to not need dsm segments
-	 * immediately. A size of 256kB seems works well and is not
-	 * disproportional compared to other constant sized shared memory
-	 * allocations. NB: To avoid DSMs further, the user can configure
-	 * min_dynamic_shared_memory.
+	 * immediately. A size of 1MB works well and is not disproportional
+	 * compared to other constant sized shared memory allocations. NB: To
+	 * avoid DSMs further, the user can configure min_dynamic_shared_memory.
 	 */
-	sz = 256 * 1024;
+	sz = 1024 * 1024;
 	Assert(dsa_minimum_size() <= sz);
 	return MAXALIGN(sz);
 }
diff --git a/src/backend/utils/activity/pgstat_wal.c b/src/backend/utils/activity/pgstat_wal.c
index ece4d91ed70..99fd20a04c2 100644
--- a/src/backend/utils/activity/pgstat_wal.c
+++ b/src/backend/utils/activity/pgstat_wal.c
@@ -60,7 +60,6 @@ pgstat_report_wal(bool force)
 
 	/* flush IO stats */
 	pgstat_flush_io(nowait);
-	(void) pgstat_flush_backend(nowait, PGSTAT_BACKEND_FLUSH_IO);
 }
 
 /*
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c26b50e0d28..d8517abed2e 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1609,32 +1609,47 @@ Datum
 pg_stat_get_backend_io(PG_FUNCTION_ARGS)
 {
 	ReturnSetInfo *rsinfo;
-	BackendType bktype;
 	int			pid;
-	PgStat_Backend *backend_stats;
-	PgStat_BktypeIO *bktype_stats;
+	PGPROC	   *proc;
+	ProcNumber	procnum;
+	PgBackendStatus *beentry;
+	BackendType bktype;
+	PgStat_BackendIO *backend_io;
 
 	InitMaterializedSRF(fcinfo, 0);
 	rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
 
 	pid = PG_GETARG_INT32(0);
-	backend_stats = pgstat_fetch_stat_backend_by_pid(pid, &bktype);
 
-	if (!backend_stats)
+	proc = BackendPidGetProc(pid);
+
+	if (!proc)
+		proc = AuxiliaryPidGetProc(pid);
+	if (!proc)
+		return (Datum) 0;
+
+	procnum = GetNumberFromPGProc(proc);
+	beentry = pgstat_get_beentry_by_proc_number(procnum);
+
+	if (!beentry || beentry->st_procpid != pid)
 		return (Datum) 0;
 
-	bktype_stats = &backend_stats->io_stats;
+	bktype = beentry->st_backendType;
+	backend_io = pgstat_fetch_stat_backend_io(procnum);
+
+	if (!backend_io)
+		return (Datum) 0;
 
 	/*
 	 * In Assert builds, we can afford an extra loop through all of the
 	 * counters (in pg_stat_io_build_tuples()), checking that only expected
 	 * stats are non-zero, since it keeps the non-Assert code cleaner.
 	 */
-	Assert(pgstat_bktype_io_stats_valid(bktype_stats, bktype));
+	Assert(pgstat_bktype_io_stats_valid(&backend_io->stats, bktype));
+
+	pg_stat_io_build_tuples(rsinfo, &backend_io->stats, bktype,
+							backend_io->stat_reset_timestamp);
 
-	/* save tuples with data from this PgStat_BktypeIO */
-	pg_stat_io_build_tuples(rsinfo, bktype_stats, bktype,
-							backend_stats->stat_reset_timestamp);
 	return (Datum) 0;
 }
 
@@ -2115,20 +2130,14 @@ pg_stat_reset_backend_stats(PG_FUNCTION_ARGS)
 	if (!beentry)
 		PG_RETURN_VOID();
 
-	/* Check if the backend type tracks statistics */
-	if (!pgstat_tracks_backend_bktype(beentry->st_backendType))
-		PG_RETURN_VOID();
-
 	/*
-	 * Accumulate the backend's WAL and lock stats into the global stats, then
-	 * zero the entries.
+	 * Accumulate the backend's WAL, lock and IO stats into the global stats,
+	 * then zero the entries.
 	 */
 	ts = GetCurrentTimestamp();
 	pgstat_wal_reset_backend_cb(procNumber, ts);
 	pgstat_lock_reset_backend_cb(procNumber, ts);
-
-	/* Reset IO stats still in PGSTAT_KIND_BACKEND */
-	pgstat_reset(PGSTAT_KIND_BACKEND, InvalidOid, procNumber);
+	pgstat_io_reset_backend_cb(procNumber, ts);
 
 	PG_RETURN_VOID();
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 3911ee56943..5d63d19673f 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -218,7 +218,7 @@ typedef struct PgStat_TableXactStatus
  * ------------------------------------------------------------
  */
 
-#define PGSTAT_FILE_FORMAT_ID	0x01A5BCBC
+#define PGSTAT_FILE_FORMAT_ID	0x01A5BCBD
 
 typedef struct PgStat_ArchiverStats
 {
@@ -333,6 +333,12 @@ typedef struct PgStat_BktypeIO
 	PgStat_Counter times[IOOBJECT_NUM_TYPES][IOCONTEXT_NUM_TYPES][IOOP_NUM_TYPES];
 } PgStat_BktypeIO;
 
+typedef struct PgStat_BackendIO
+{
+	TimestampTz stat_reset_timestamp;
+	PgStat_BktypeIO stats;
+} PgStat_BackendIO;
+
 typedef struct PgStat_PendingIO
 {
 	uint64		bytes[IOOBJECT_NUM_TYPES][IOCONTEXT_NUM_TYPES][IOOP_NUM_TYPES];
@@ -514,28 +520,6 @@ typedef struct PgStat_WalStats
 	TimestampTz stat_reset_timestamp;
 } PgStat_WalStats;
 
-/* -------
- * PgStat_Backend		Backend statistics
- * -------
- */
-typedef struct PgStat_Backend
-{
-	TimestampTz stat_reset_timestamp;
-	PgStat_BktypeIO io_stats;
-} PgStat_Backend;
-
-/* ---------
- * PgStat_BackendPending	Non-flushed backend stats.
- * ---------
- */
-typedef struct PgStat_BackendPending
-{
-	/*
-	 * Backend statistics store the same amount of IO data as PGSTAT_KIND_IO.
-	 */
-	PgStat_PendingIO pending_io;
-} PgStat_BackendPending;
-
 /*
  * Functions in pgstat.c
  */
@@ -572,27 +556,6 @@ extern bool pgstat_have_entry(PgStat_Kind kind, Oid dboid, uint64 objid);
 extern void pgstat_report_archiver(const char *xlog, bool failed);
 extern PgStat_ArchiverStats *pgstat_fetch_stat_archiver(void);
 
-/*
- * Functions in pgstat_backend.c
- */
-
-/* used by pgstat_io.c for I/O stats tracked in backends */
-extern void pgstat_count_backend_io_op_time(IOObject io_object,
-											IOContext io_context,
-											IOOp io_op,
-											instr_time io_time);
-extern void pgstat_count_backend_io_op(IOObject io_object,
-									   IOContext io_context,
-									   IOOp io_op, uint32 cnt,
-									   uint64 bytes);
-
-
-extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
-extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
-														BackendType *bktype);
-extern bool pgstat_tracks_backend_bktype(BackendType bktype);
-extern void pgstat_create_backend(ProcNumber procnum);
-
 /*
  * Functions in pgstat_bgwriter.c
  */
@@ -623,6 +586,8 @@ extern void pgstat_count_io_op_time(IOObject io_object, IOContext io_context,
 									uint32 cnt, uint64 bytes);
 
 extern PgStat_IO *pgstat_fetch_stat_io(void);
+extern PgStat_BackendIO *pgstat_fetch_stat_backend_io(ProcNumber procnum);
+extern void pgstat_io_reset_backend_cb(ProcNumber procnum, TimestampTz ts);
 extern const char *pgstat_get_io_context_name(IOContext io_context);
 extern const char *pgstat_get_io_object_name(IOObject io_object);
 
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index 9a765eca359..4e4603fe5b1 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -477,12 +477,13 @@ typedef struct PgStatShared_Checkpointer
 /* Shared-memory ready PgStat_IO */
 typedef struct PgStatShared_IO
 {
+	LWLock		lock;
+	PgStat_IO	stats;
+
 	/*
-	 * locks[i] protects stats.stats[i]. locks[0] also protects
-	 * stats.stat_reset_timestamp.
+	 * Per-backend dshash, keyed by ProcNumber.
 	 */
-	LWLock		locks[BACKEND_NUM_TYPES];
-	PgStat_IO	stats;
+	dshash_table_handle backend_hash_handle;
 } PgStatShared_IO;
 
 typedef struct PgStatShared_Lock
@@ -513,6 +514,16 @@ typedef struct PgStatShared_PerBackendEntry
 	LWLock		lock;
 } PgStatShared_PerBackendEntry;
 
+/*
+ * Per-backend entry for IO statistics, stored in a dshash keyed by
+ * ProcNumber.
+ */
+typedef struct PgStatShared_IOBackendEntry
+{
+	PgStatShared_PerBackendEntry header;
+	PgStat_BackendIO stats;
+} PgStatShared_IOBackendEntry;
+
 /*
  * Per-backend entry for lock statistics, stored in a dshash keyed by
  * ProcNumber.
@@ -584,12 +595,6 @@ typedef struct PgStatShared_ReplSlot
 	PgStat_StatReplSlotEntry stats;
 } PgStatShared_ReplSlot;
 
-typedef struct PgStatShared_Backend
-{
-	PgStatShared_Common header;
-	PgStat_Backend stats;
-} PgStatShared_Backend;
-
 /*
  * Central shared memory entry for the cumulative stats system.
  *
@@ -770,19 +775,6 @@ extern void pgstat_archiver_init_shmem_cb(void *stats);
 extern void pgstat_archiver_reset_all_cb(TimestampTz ts);
 extern void pgstat_archiver_snapshot_cb(void);
 
-/*
- * Functions in pgstat_backend.c
- */
-
-/* flags for pgstat_flush_backend() */
-#define PGSTAT_BACKEND_FLUSH_IO		(1 << 0)	/* Flush I/O statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL   (PGSTAT_BACKEND_FLUSH_IO)
-
-extern bool pgstat_flush_backend(bool nowait, uint32 flags);
-extern bool pgstat_backend_flush_cb(bool nowait);
-extern void pgstat_backend_reset_timestamp_cb(PgStatShared_Common *header,
-											  TimestampTz ts);
-
 /*
  * Functions in pgstat_bgwriter.c
  */
@@ -833,6 +825,9 @@ extern bool pgstat_io_flush_cb(bool nowait);
 extern void pgstat_io_init_shmem_cb(void *stats);
 extern void pgstat_io_reset_all_cb(TimestampTz ts);
 extern void pgstat_io_snapshot_cb(void);
+extern void pgstat_io_acc_backend_cb(void);
+extern void pgstat_io_acc_all_backends(void);
+extern void pgstat_io_per_backend_acc_cb(void *dst, void *entry);
 
 /*
  * Functions in pgstat_lock.c
diff --git a/src/include/utils/pgstat_kind.h b/src/include/utils/pgstat_kind.h
index 2d78a029683..6d53d8e53c6 100644
--- a/src/include/utils/pgstat_kind.h
+++ b/src/include/utils/pgstat_kind.h
@@ -29,16 +29,15 @@
 #define PGSTAT_KIND_FUNCTION	3	/* per-function statistics */
 #define PGSTAT_KIND_REPLSLOT	4	/* per-slot statistics */
 #define PGSTAT_KIND_SUBSCRIPTION	5	/* per-subscription statistics */
-#define PGSTAT_KIND_BACKEND	6	/* per-backend statistics */
 
 /* stats for fixed-numbered objects */
-#define PGSTAT_KIND_ARCHIVER	7
-#define PGSTAT_KIND_BGWRITER	8
-#define PGSTAT_KIND_CHECKPOINTER	9
-#define PGSTAT_KIND_IO	10
-#define PGSTAT_KIND_LOCK	11
-#define PGSTAT_KIND_SLRU	12
-#define PGSTAT_KIND_WAL	13
+#define PGSTAT_KIND_ARCHIVER	6
+#define PGSTAT_KIND_BGWRITER	7
+#define PGSTAT_KIND_CHECKPOINTER	8
+#define PGSTAT_KIND_IO	9
+#define PGSTAT_KIND_LOCK	10
+#define PGSTAT_KIND_SLRU	11
+#define PGSTAT_KIND_WAL	12
 
 #define PGSTAT_KIND_BUILTIN_MIN PGSTAT_KIND_DATABASE
 #define PGSTAT_KIND_BUILTIN_MAX PGSTAT_KIND_WAL
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index fae5f939523..e4369221ef3 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -119,15 +119,14 @@ SELECT id, name, fixed_amount,
   3 | function     | f            | f         | t
   4 | replslot     | f            | t         | t
   5 | subscription | f            | t         | t
-  6 | backend      | f            | t         | f
-  7 | archiver     | t            | f         | t
-  8 | bgwriter     | t            | f         | t
-  9 | checkpointer | t            | f         | t
- 10 | io           | t            | f         | t
- 11 | lock         | t            | f         | t
- 12 | slru         | t            | f         | t
- 13 | wal          | t            | f         | t
-(13 rows)
+  6 | archiver     | t            | f         | t
+  7 | bgwriter     | t            | f         | t
+  8 | checkpointer | t            | f         | t
+  9 | io           | t            | f         | t
+ 10 | lock         | t            | f         | t
+ 11 | slru         | t            | f         | t
+ 12 | wal          | t            | f         | t
+(12 rows)
 
 -- ensure that both seqscan and indexscan plans are allowed
 SET enable_seqscan TO on;
@@ -1870,13 +1869,20 @@ SELECT :io_stats_post_reset < :io_stats_pre_reset;
 
 SELECT sum(evictions) + sum(reuses) + sum(extends) + sum(fsyncs) + sum(reads) + sum(writes) + sum(writebacks) + sum(hits) AS my_io_stats_post_reset
   FROM pg_stat_get_backend_io(pg_backend_pid()) \gset
--- pg_stat_reset_shared() did not reset backend IO stats
-SELECT :my_io_stats_pre_reset <= :my_io_stats_post_reset;
+-- pg_stat_reset_shared() also resets per-backend IO stats
+SELECT :my_io_stats_pre_reset > :my_io_stats_post_reset;
  ?column? 
 ----------
  t
 (1 row)
 
+SELECT bool_and(stats_reset IS NOT NULL) AS backend_io_reset_timestamp_set
+  FROM pg_stat_get_backend_io(pg_backend_pid());
+ backend_io_reset_timestamp_set 
+--------------------------------
+ t
+(1 row)
+
 -- but pg_stat_reset_backend_stats() does
 SELECT pg_stat_reset_backend_stats(pg_backend_pid());
  pg_stat_reset_backend_stats 
@@ -1903,11 +1909,13 @@ SELECT pg_stat_get_backend_io(0);
 ------------------------
 (0 rows)
 
--- Auxiliary processes return no data.
-SELECT pg_stat_get_backend_io(:checkpointer_pid);
- pg_stat_get_backend_io 
-------------------------
-(0 rows)
+-- Auxiliary processes now return data
+SELECT count(*) > 0 AS checkpointer_has_io_stats
+  FROM pg_stat_get_backend_io(:checkpointer_pid);
+ checkpointer_has_io_stats 
+---------------------------
+ t
+(1 row)
 
 -- test BRIN index doesn't block HOT update
 CREATE TABLE brin_hot (
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index c17753dcd20..d5877cd8404 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -878,8 +878,10 @@ SELECT sum(evictions) + sum(reuses) + sum(extends) + sum(fsyncs) + sum(reads) +
 SELECT :io_stats_post_reset < :io_stats_pre_reset;
 SELECT sum(evictions) + sum(reuses) + sum(extends) + sum(fsyncs) + sum(reads) + sum(writes) + sum(writebacks) + sum(hits) AS my_io_stats_post_reset
   FROM pg_stat_get_backend_io(pg_backend_pid()) \gset
--- pg_stat_reset_shared() did not reset backend IO stats
-SELECT :my_io_stats_pre_reset <= :my_io_stats_post_reset;
+-- pg_stat_reset_shared() also resets per-backend IO stats
+SELECT :my_io_stats_pre_reset > :my_io_stats_post_reset;
+SELECT bool_and(stats_reset IS NOT NULL) AS backend_io_reset_timestamp_set
+  FROM pg_stat_get_backend_io(pg_backend_pid());
 -- but pg_stat_reset_backend_stats() does
 SELECT pg_stat_reset_backend_stats(pg_backend_pid());
 SELECT sum(evictions) + sum(reuses) + sum(extends) + sum(fsyncs) + sum(reads) + sum(writes) + sum(writebacks) + sum(hits) AS my_io_stats_post_backend_reset
@@ -889,8 +891,9 @@ SELECT :my_io_stats_pre_reset > :my_io_stats_post_backend_reset;
 -- Check invalid input for pg_stat_get_backend_io()
 SELECT pg_stat_get_backend_io(NULL);
 SELECT pg_stat_get_backend_io(0);
--- Auxiliary processes return no data.
-SELECT pg_stat_get_backend_io(:checkpointer_pid);
+-- Auxiliary processes now return data
+SELECT count(*) > 0 AS checkpointer_has_io_stats
+  FROM pg_stat_get_backend_io(:checkpointer_pid);
 
 -- test BRIN index doesn't block HOT update
 CREATE TABLE brin_hot (
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index d89fccf482d..52de6e93c31 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2316,7 +2316,6 @@ PgFdwSamplingMethod
 PgFdwScanState
 PgIfAddrCallback
 PgStatShared_Archiver
-PgStatShared_Backend
 PgStatShared_BgWriter
 PgStatShared_Checkpointer
 PgStatShared_Common
@@ -2326,6 +2325,7 @@ PgStatShared_Database
 PgStatShared_Function
 PgStatShared_HashEntry
 PgStatShared_IO
+PgStatShared_IOBackendEntry
 PgStatShared_Lock
 PgStatShared_LockBackendEntry
 PgStatShared_PerBackendEntry
@@ -2336,8 +2336,7 @@ PgStatShared_Subscription
 PgStatShared_Wal
 PgStatShared_WalBackendEntry
 PgStat_ArchiverStats
-PgStat_Backend
-PgStat_BackendPending
+PgStat_BackendIO
 PgStat_BackendSubEntry
 PgStat_BgWriterStats
 PgStat_BktypeIO
-- 
2.34.1

--Hx3mnhNtand64WhS--