v27-0004-Add-system-view-tracking-IO-ops-per-backend-type.patch

From 17036e78a92a75da83ea7811fd738d490fc6c65e Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Thu, 11 Aug 2022 18:28:50 -0400
Subject: [PATCH v27 4/4] Add system view tracking IO ops per backend type

Add pg_stat_io, a system view which tracks the number of IOOp (allocs,
extends, fsyncs, reads, and writes) done through each IOContext (shared
buffers, local buffers, strategy buffers) by each type of backend (e.g.
client backend, checkpointer).

Some BackendTypes do not accumulate IO operations statistics and will
not be included in the view.

Some IOContexts are not used by some BackendTypes and will not be in the
view. For example, checkpointer does not use a BufferAccessStrategy
(currently), so there will be no row for the "strategy" IOContext for
checkpointer.

Some IOOps are invalid in combination with certain IOContexts. Those
cells will be NULL in the view to distinguish between 0 observed IOOps
of that type and an invalid combination. For example, local buffers are
not fsync'd so cells for all BackendTypes for IOCONTEXT_STRATEGY and
IOOP_FSYNC will be NULL.

Some BackendTypes never perform certain IOOps. Those cells will also be
NULL in the view. For example, bgwriter should not perform reads.

View stats are fetched from statistics incremented when a backend
performs an IO Operation and maintained by the cumulative statistics
subsystem.

Each row of the view is stats for a particular BackendType for a
particular IOContext (e.g. shared buffer accesses by checkpointer) and
each column in the view is the total number of IO Operations done (e.g.
writes).
So a cell in the view would be, for example, the number of shared
buffers written by checkpointer since the last stats reset.

Note that some of the cells in the view are redundant with fields in
pg_stat_bgwriter (e.g. buffers_backend), however these have been kept in
pg_stat_bgwriter for backwards compatibility. Deriving the redundant
pg_stat_bgwriter stats from the IO operations stats structures was also
problematic due to the separate reset targets for 'bgwriter' and
'io'.

Suggested by Andres Freund

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/20200124195226.lth52iydq2n2uilq%40alap3.anarazel.de
---
 doc/src/sgml/monitoring.sgml         | 115 ++++++++++++++-
 src/backend/catalog/system_views.sql |  12 ++
 src/backend/utils/adt/pgstatfuncs.c  | 102 ++++++++++++++
 src/include/catalog/pg_proc.dat      |   9 ++
 src/test/regress/expected/rules.out  |   9 ++
 src/test/regress/expected/stats.out  | 201 +++++++++++++++++++++++++++
 src/test/regress/sql/stats.sql       | 103 ++++++++++++++
 7 files changed, 550 insertions(+), 1 deletion(-)

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 14d97ec92c..98750121c5 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -448,6 +448,15 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
      </entry>
      </row>
 
+     <row>
+      <entry><structname>pg_stat_io</structname><indexterm><primary>pg_stat_io</primary></indexterm></entry>
+      <entry>A row for each IO Context for each backend type showing
+      statistics about backend IO operations. See
+       <link linkend="monitoring-pg-stat-io-view">
+       <structname>pg_stat_io</structname></link> for details.
+     </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_wal</structname><indexterm><primary>pg_stat_wal</primary></indexterm></entry>
       <entry>One row only, showing statistics about WAL activity. See
@@ -3600,7 +3609,111 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
        <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
       </para>
       <para>
-       Time at which these statistics were last reset
+       Time at which these statistics were last reset.
+      </para></entry>
+     </row>
+    </tbody>
+   </tgroup>
+  </table>
+
+ </sect2>
+
+ <sect2 id="monitoring-pg-stat-io-view">
+  <title><structname>pg_stat_io</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_io</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_io</structname> view has a row for each backend
+   type for each possible IO Context containing global data for the cluster for
+   that backend and IO Context.
+  </para>
+
+  <table id="pg-stat-io-view" xreflabel="pg_stat_io">
+   <title><structname>pg_stat_io</structname> View</title>
+   <tgroup cols="1">
+    <thead>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       Column Type
+      </para>
+      <para>
+       Description
+      </para></entry>
+     </row>
+    </thead>
+    <tbody>
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>backend_type</structfield> <type>text</type>
+      </para>
+      <para>
+       Type of backend (e.g. background worker, autovacuum worker).
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>io_context</structfield> <type>text</type>
+      </para>
+      <para>
+       IO Context used (e.g. shared buffers, direct).
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>alloc</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of buffers allocated.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>extend</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of blocks extended.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>fsync</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of blocks fsynced.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>read</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of blocks read.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>write</structfield> <type>bigint</type>
+      </para>
+      <para>
+       Number of blocks written.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
+      </para>
+      <para>
+       Time at which these statistics were last reset.
       </para></entry>
      </row>
     </tbody>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index f369b1fc14..5fab964219 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -1115,6 +1115,18 @@ CREATE VIEW pg_stat_bgwriter AS
         pg_stat_get_buf_alloc() AS buffers_alloc,
         pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
 
+CREATE VIEW pg_stat_io AS
+SELECT
+       b.backend_type,
+       b.io_context,
+       b.alloc,
+       b.extend,
+       b.fsync,
+       b.read,
+       b.write,
+       b.stats_reset
+FROM pg_stat_get_io() b;
+
 CREATE VIEW pg_stat_wal AS
     SELECT
         w.wal_records,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index cda4447e53..821216d01e 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1733,6 +1733,108 @@ pg_stat_get_buf_alloc(PG_FUNCTION_ARGS)
 	PG_RETURN_INT64(pgstat_fetch_stat_bgwriter()->buf_alloc);
 }
 
+Datum
+pg_stat_get_io(PG_FUNCTION_ARGS)
+{
+	PgStat_BackendIOContextOps *backends_io_stats;
+	ReturnSetInfo *rsinfo;
+	Datum		reset_time;
+
+	/*
+	 * When adding a new column to the pg_stat_io view, add a new enum value
+	 * here above IO_NUM_COLUMNS.
+	 */
+	enum
+	{
+		IO_COLUMN_BACKEND_TYPE,
+		IO_COLUMN_IO_CONTEXT,
+		IO_COLUMN_ALLOCS,
+		IO_COLUMN_EXTENDS,
+		IO_COLUMN_FSYNCS,
+		IO_COLUMN_READS,
+		IO_COLUMN_WRITES,
+		IO_COLUMN_RESET_TIME,
+		IO_NUM_COLUMNS,
+	};
+
+#define IO_COLUMN_IOOP_OFFSET (IO_COLUMN_IO_CONTEXT + 1)
+
+	SetSingleFuncCall(fcinfo, 0);
+	rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	backends_io_stats = pgstat_fetch_backend_io_context_ops();
+
+	reset_time = TimestampTzGetDatum(backends_io_stats->stat_reset_timestamp);
+
+	for (int bktype = 0; bktype < BACKEND_NUM_TYPES; bktype++)
+	{
+		Datum		bktype_desc = CStringGetTextDatum(GetBackendTypeDesc(bktype));
+		PgStat_IOContextOps *io_context_ops = &backends_io_stats->stats[bktype];
+
+		/*
+		 * For those BackendTypes without IO Operation stats, skip
+		 * representing them in the view altogether.
+		 */
+		if (!pgstat_io_op_stats_collected(bktype))
+		{
+			for (int io_context = 0; io_context < IOCONTEXT_NUM_TYPES; io_context++)
+				pgstat_io_context_ops_assert_zero(&io_context_ops->data[io_context]);
+			continue;
+		}
+
+		for (int io_context = 0; io_context < IOCONTEXT_NUM_TYPES; io_context++)
+		{
+			PgStat_IOOpCounters *counters = &io_context_ops->data[io_context];
+			Datum		values[IO_NUM_COLUMNS];
+			bool		nulls[IO_NUM_COLUMNS];
+
+			/*
+			 * Some combinations of IOCONTEXT and BackendType are not valid
+			 * for any type of IO Operation. In such cases, omit the entire
+			 * row from the view.
+			 */
+			if (!pgstat_bktype_io_context_valid(bktype, io_context))
+			{
+				pgstat_io_context_ops_assert_zero(counters);
+				continue;
+			}
+
+			memset(values, 0, sizeof(values));
+			memset(nulls, 0, sizeof(nulls));
+
+			values[IO_COLUMN_BACKEND_TYPE] = bktype_desc;
+			values[IO_COLUMN_IO_CONTEXT] = CStringGetTextDatum(
+															   pgstat_io_context_desc(io_context));
+			values[IO_COLUMN_ALLOCS] = Int64GetDatum(counters->allocs);
+			values[IO_COLUMN_EXTENDS] = Int64GetDatum(counters->extends);
+			values[IO_COLUMN_FSYNCS] = Int64GetDatum(counters->fsyncs);
+			values[IO_COLUMN_READS] = Int64GetDatum(counters->reads);
+			values[IO_COLUMN_WRITES] = Int64GetDatum(counters->writes);
+			values[IO_COLUMN_RESET_TIME] = TimestampTzGetDatum(reset_time);
+
+
+			/*
+			 * Some combinations of BackendType and IOOp and of IOContext and
+			 * IOOp are not valid. Set these cells in the view NULL and assert
+			 * that these stats are zero as expected.
+			 */
+			for (int io_op = 0; io_op < IOOP_NUM_TYPES; io_op++)
+			{
+				if (!pgstat_bktype_io_op_valid(bktype, io_op) ||
+					!pgstat_io_context_io_op_valid(io_context, io_op))
+				{
+					pgstat_io_op_assert_zero(counters, io_op);
+					nulls[io_op + IO_COLUMN_IOOP_OFFSET] = true;
+				}
+			}
+
+			tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+		}
+	}
+
+	return (Datum) 0;
+}
+
 /*
  * Returns statistics of WAL activity
  */
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index be47583122..4aefebc7f8 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5646,6 +5646,15 @@
   proname => 'pg_stat_get_buf_alloc', provolatile => 's', proparallel => 'r',
   prorettype => 'int8', proargtypes => '', prosrc => 'pg_stat_get_buf_alloc' },
 
+{ oid => '8459', descr => 'statistics: per backend type IO statistics',
+  proname => 'pg_stat_get_io', provolatile => 'v',
+  prorows => '14', proretset => 't',
+  proparallel => 'r', prorettype => 'record', proargtypes => '',
+  proallargtypes => '{text,text,int8,int8,int8,int8,int8,timestamptz}',
+  proargmodes => '{o,o,o,o,o,o,o,o}',
+  proargnames => '{backend_type,io_context,alloc,extend,fsync,read,write,stats_reset}',
+  prosrc => 'pg_stat_get_io' },
+
 { oid => '1136', descr => 'statistics: information about WAL activity',
   proname => 'pg_stat_get_wal', proisstrict => 'f', provolatile => 's',
   proparallel => 'r', prorettype => 'record', proargtypes => '',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 7ec3d2688f..d122c36556 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1873,6 +1873,15 @@ pg_stat_gssapi| SELECT s.pid,
     s.gss_enc AS encrypted
    FROM pg_stat_get_activity(NULL::integer) s(datid, pid, usesysid, application_name, state, query, wait_event_type, wait_event, xact_start, query_start, backend_start, state_change, client_addr, client_hostname, client_port, backend_xid, backend_xmin, backend_type, ssl, sslversion, sslcipher, sslbits, ssl_client_dn, ssl_client_serial, ssl_issuer_dn, gss_auth, gss_princ, gss_enc, leader_pid, query_id)
   WHERE (s.client_port IS NOT NULL);
+pg_stat_io| SELECT b.backend_type,
+    b.io_context,
+    b.alloc,
+    b.extend,
+    b.fsync,
+    b.read,
+    b.write,
+    b.stats_reset
+   FROM pg_stat_get_io() b(backend_type, io_context, alloc, extend, fsync, read, write, stats_reset);
 pg_stat_progress_analyze| SELECT s.pid,
     s.datid,
     d.datname,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 6b233ff4c0..a75fc91c57 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -796,4 +796,205 @@ SELECT pg_stat_get_subscription_stats(NULL);
  
 (1 row)
 
+-- Test that allocs, extends, reads, and writes to Shared Buffers and fsyncs
+-- done to ensure durability of Shared Buffers are tracked in pg_stat_io.
+SELECT sum(alloc) AS io_sum_shared_allocs_before FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(extend) AS io_sum_shared_extends_before FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(fsync) AS io_sum_shared_fsyncs_before FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(read) AS io_sum_shared_reads_before FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(write) AS io_sum_shared_writes_before FROM pg_stat_io WHERE io_context = 'Shared' \gset
+-- Create a regular table and insert some data to generate IOCONTEXT_SHARED allocs and extends.
+CREATE TABLE test_io_shared(a int);
+INSERT INTO test_io_shared SELECT i FROM generate_series(1,100)i;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+-- After a checkpoint, there should be some additional IOCONTEXT_SHARED writes and fsyncs.
+CHECKPOINT;
+SELECT sum(alloc) AS io_sum_shared_allocs_after FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(extend) AS io_sum_shared_extends_after FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(write) AS io_sum_shared_writes_after FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(fsync) AS io_sum_shared_fsyncs_after FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT :io_sum_shared_allocs_after > :io_sum_shared_allocs_before;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT :io_sum_shared_extends_after > :io_sum_shared_extends_before;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT current_setting('fsync') = 'off' OR :io_sum_shared_fsyncs_after > :io_sum_shared_fsyncs_before;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT :io_sum_shared_writes_after > :io_sum_shared_writes_before;
+ ?column? 
+----------
+ t
+(1 row)
+
+-- Change the tablespace so that the table is rewritten directly, then SELECT
+-- from it to cause it to be read back into Shared Buffers.
+SET allow_in_place_tablespaces = true;
+CREATE TABLESPACE test_io_shared_stats_tblspc LOCATION '';
+ALTER TABLE test_io_shared SET TABLESPACE test_io_shared_stats_tblspc;
+SELECT COUNT(*) FROM test_io_shared;
+ count 
+-------
+   100
+(1 row)
+
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT sum(read) AS io_sum_shared_reads_after FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT :io_sum_shared_reads_after > :io_sum_shared_reads_before;
+ ?column? 
+----------
+ t
+(1 row)
+
+DROP TABLE test_io_shared;
+DROP TABLESPACE test_io_shared_stats_tblspc;
+-- Test that allocs, extends, reads, and writes of temporary tables are tracked
+-- in pg_stat_io.
+CREATE TEMPORARY TABLE test_io_local(a int, b TEXT);
+SELECT sum(alloc) AS io_sum_local_allocs_before FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT sum(extend) AS io_sum_local_extends_before FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT sum(read) AS io_sum_local_reads_before FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT sum(write) AS io_sum_local_writes_before FROM pg_stat_io WHERE io_context = 'Local' \gset
+-- Insert enough values that we need to reuse and write out dirty local
+-- buffers.
+INSERT INTO test_io_local SELECT generate_series(1, 80000) as id,
+'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';
+-- Read in evicted buffers.
+SELECT COUNT(*) FROM test_io_local;
+ count 
+-------
+ 80000
+(1 row)
+
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT sum(alloc) AS io_sum_local_allocs_after FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT sum(extend) AS io_sum_local_extends_after FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT sum(read) AS io_sum_local_reads_after FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT sum(write) AS io_sum_local_writes_after FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT :io_sum_local_allocs_after > :io_sum_local_allocs_before;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT :io_sum_local_extends_after > :io_sum_local_extends_before;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT :io_sum_local_reads_after > :io_sum_local_reads_before;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT :io_sum_local_writes_after > :io_sum_local_writes_before;
+ ?column? 
+----------
+ t
+(1 row)
+
+-- Test that, when using a Strategy, reusing buffers from the Strategy ring
+-- count as "Strategy" allocs in pg_stat_io. Also test that Strategy reads are
+-- counted as such.
+-- Set wal_skip_threshold smaller than the expected size of test_io_strategy so
+-- that, even if wal_level is minimal, VACUUM FULL will fsync the newly
+-- rewritten test_io_strategy instead of writing it to WAL. Writing it to WAL
+-- will result in the newly written relation pages being in shared buffers --
+-- preventing us from testing BufferAccessStrategy allocs and reads.
+SET wal_skip_threshold = '1 kB';
+SELECT sum(alloc) AS io_sum_strategy_allocs_before FROM pg_stat_io WHERE io_context = 'Strategy' \gset
+SELECT sum(read) AS io_sum_strategy_reads_before FROM pg_stat_io WHERE io_context = 'Strategy' \gset
+CREATE TABLE test_io_strategy(a INT, b INT);
+ALTER TABLE test_io_strategy SET (autovacuum_enabled = 'false');
+INSERT INTO test_io_strategy SELECT i, i from generate_series(1, 8000)i;
+-- Ensure that the next VACUUM will need to perform IO by rewriting the table
+-- first with VACUUM (FULL).
+VACUUM (FULL) test_io_strategy;
+VACUUM (PARALLEL 0) test_io_strategy;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT sum(alloc) AS io_sum_strategy_allocs_after FROM pg_stat_io WHERE io_context = 'Strategy' \gset
+SELECT sum(read) AS io_sum_strategy_reads_after FROM pg_stat_io WHERE io_context = 'Strategy' \gset
+SELECT :io_sum_strategy_allocs_after > :io_sum_strategy_allocs_before;
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT :io_sum_strategy_reads_after > :io_sum_strategy_reads_before;
+ ?column? 
+----------
+ t
+(1 row)
+
+DROP TABLE test_io_strategy;
+-- Hope that the previous value of wal_skip_threshold was the default. We
+-- can't use BEGIN...SET LOCAL since VACUUM can't be run inside a transaction
+-- block.
+RESET wal_skip_threshold;
+-- Test that, when using a Strategy, if creating a relation, Strategy extends
+-- are counted in pg_stat_io.
+-- A CTAS uses a Bulkwrite strategy.
+SELECT sum(extend) AS io_sum_strategy_extends_before FROM pg_stat_io WHERE io_context = 'Strategy' \gset
+CREATE TABLE test_io_strategy_extend AS SELECT i FROM generate_series(1,100)i;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT sum(extend) AS io_sum_strategy_extends_after FROM pg_stat_io WHERE io_context = 'Strategy' \gset
+SELECT :io_sum_strategy_extends_after > :io_sum_strategy_extends_before;
+ ?column? 
+----------
+ t
+(1 row)
+
+DROP TABLE test_io_strategy_extend;
+-- Test stats reset
+SELECT sum(alloc) + sum(extend) + sum(fsync) + sum(read) + sum(write) AS io_stats_pre_reset FROM pg_stat_io \gset
+SELECT pg_stat_reset_shared('io');
+ pg_stat_reset_shared 
+----------------------
+ 
+(1 row)
+
+SELECT sum(alloc) + sum(extend) + sum(fsync) + sum(read) + sum(write) AS io_stats_post_reset FROM pg_stat_io \gset
+SELECT :io_stats_post_reset < :io_stats_pre_reset;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- End of Stats Test
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 096f00ce8b..090cc67296 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -396,4 +396,107 @@ SELECT pg_stat_get_replication_slot(NULL);
 SELECT pg_stat_get_subscription_stats(NULL);
 
 
+
+-- Test that allocs, extends, reads, and writes to Shared Buffers and fsyncs
+-- done to ensure durability of Shared Buffers are tracked in pg_stat_io.
+SELECT sum(alloc) AS io_sum_shared_allocs_before FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(extend) AS io_sum_shared_extends_before FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(fsync) AS io_sum_shared_fsyncs_before FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(read) AS io_sum_shared_reads_before FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(write) AS io_sum_shared_writes_before FROM pg_stat_io WHERE io_context = 'Shared' \gset
+-- Create a regular table and insert some data to generate IOCONTEXT_SHARED allocs and extends.
+CREATE TABLE test_io_shared(a int);
+INSERT INTO test_io_shared SELECT i FROM generate_series(1,100)i;
+SELECT pg_stat_force_next_flush();
+-- After a checkpoint, there should be some additional IOCONTEXT_SHARED writes and fsyncs.
+CHECKPOINT;
+SELECT sum(alloc) AS io_sum_shared_allocs_after FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(extend) AS io_sum_shared_extends_after FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(write) AS io_sum_shared_writes_after FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT sum(fsync) AS io_sum_shared_fsyncs_after FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT :io_sum_shared_allocs_after > :io_sum_shared_allocs_before;
+SELECT :io_sum_shared_extends_after > :io_sum_shared_extends_before;
+SELECT current_setting('fsync') = 'off' OR :io_sum_shared_fsyncs_after > :io_sum_shared_fsyncs_before;
+SELECT :io_sum_shared_writes_after > :io_sum_shared_writes_before;
+-- Change the tablespace so that the table is rewritten directly, then SELECT
+-- from it to cause it to be read back into Shared Buffers.
+SET allow_in_place_tablespaces = true;
+CREATE TABLESPACE test_io_shared_stats_tblspc LOCATION '';
+ALTER TABLE test_io_shared SET TABLESPACE test_io_shared_stats_tblspc;
+SELECT COUNT(*) FROM test_io_shared;
+SELECT pg_stat_force_next_flush();
+SELECT sum(read) AS io_sum_shared_reads_after FROM pg_stat_io WHERE io_context = 'Shared' \gset
+SELECT :io_sum_shared_reads_after > :io_sum_shared_reads_before;
+DROP TABLE test_io_shared;
+DROP TABLESPACE test_io_shared_stats_tblspc;
+
+-- Test that allocs, extends, reads, and writes of temporary tables are tracked
+-- in pg_stat_io.
+CREATE TEMPORARY TABLE test_io_local(a int, b TEXT);
+SELECT sum(alloc) AS io_sum_local_allocs_before FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT sum(extend) AS io_sum_local_extends_before FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT sum(read) AS io_sum_local_reads_before FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT sum(write) AS io_sum_local_writes_before FROM pg_stat_io WHERE io_context = 'Local' \gset
+-- Insert enough values that we need to reuse and write out dirty local
+-- buffers.
+INSERT INTO test_io_local SELECT generate_series(1, 80000) as id,
+'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';
+-- Read in evicted buffers.
+SELECT COUNT(*) FROM test_io_local;
+SELECT pg_stat_force_next_flush();
+SELECT sum(alloc) AS io_sum_local_allocs_after FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT sum(extend) AS io_sum_local_extends_after FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT sum(read) AS io_sum_local_reads_after FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT sum(write) AS io_sum_local_writes_after FROM pg_stat_io WHERE io_context = 'Local' \gset
+SELECT :io_sum_local_allocs_after > :io_sum_local_allocs_before;
+SELECT :io_sum_local_extends_after > :io_sum_local_extends_before;
+SELECT :io_sum_local_reads_after > :io_sum_local_reads_before;
+SELECT :io_sum_local_writes_after > :io_sum_local_writes_before;
+
+-- Test that, when using a Strategy, reusing buffers from the Strategy ring
+-- count as "Strategy" allocs in pg_stat_io. Also test that Strategy reads are
+-- counted as such.
+
+-- Set wal_skip_threshold smaller than the expected size of test_io_strategy so
+-- that, even if wal_level is minimal, VACUUM FULL will fsync the newly
+-- rewritten test_io_strategy instead of writing it to WAL. Writing it to WAL
+-- will result in the newly written relation pages being in shared buffers --
+-- preventing us from testing BufferAccessStrategy allocs and reads.
+SET wal_skip_threshold = '1 kB';
+SELECT sum(alloc) AS io_sum_strategy_allocs_before FROM pg_stat_io WHERE io_context = 'Strategy' \gset
+SELECT sum(read) AS io_sum_strategy_reads_before FROM pg_stat_io WHERE io_context = 'Strategy' \gset
+CREATE TABLE test_io_strategy(a INT, b INT);
+ALTER TABLE test_io_strategy SET (autovacuum_enabled = 'false');
+INSERT INTO test_io_strategy SELECT i, i from generate_series(1, 8000)i;
+-- Ensure that the next VACUUM will need to perform IO by rewriting the table
+-- first with VACUUM (FULL).
+VACUUM (FULL) test_io_strategy;
+VACUUM (PARALLEL 0) test_io_strategy;
+SELECT pg_stat_force_next_flush();
+SELECT sum(alloc) AS io_sum_strategy_allocs_after FROM pg_stat_io WHERE io_context = 'Strategy' \gset
+SELECT sum(read) AS io_sum_strategy_reads_after FROM pg_stat_io WHERE io_context = 'Strategy' \gset
+SELECT :io_sum_strategy_allocs_after > :io_sum_strategy_allocs_before;
+SELECT :io_sum_strategy_reads_after > :io_sum_strategy_reads_before;
+DROP TABLE test_io_strategy;
+-- Hope that the previous value of wal_skip_threshold was the default. We
+-- can't use BEGIN...SET LOCAL since VACUUM can't be run inside a transaction
+-- block.
+RESET wal_skip_threshold;
+
+-- Test that, when using a Strategy, if creating a relation, Strategy extends
+-- are counted in pg_stat_io.
+-- A CTAS uses a Bulkwrite strategy.
+SELECT sum(extend) AS io_sum_strategy_extends_before FROM pg_stat_io WHERE io_context = 'Strategy' \gset
+CREATE TABLE test_io_strategy_extend AS SELECT i FROM generate_series(1,100)i;
+SELECT pg_stat_force_next_flush();
+SELECT sum(extend) AS io_sum_strategy_extends_after FROM pg_stat_io WHERE io_context = 'Strategy' \gset
+SELECT :io_sum_strategy_extends_after > :io_sum_strategy_extends_before;
+DROP TABLE test_io_strategy_extend;
+
+-- Test stats reset
+SELECT sum(alloc) + sum(extend) + sum(fsync) + sum(read) + sum(write) AS io_stats_pre_reset FROM pg_stat_io \gset
+SELECT pg_stat_reset_shared('io');
+SELECT sum(alloc) + sum(extend) + sum(fsync) + sum(read) + sum(write) AS io_stats_post_reset FROM pg_stat_io \gset
+SELECT :io_stats_post_reset < :io_stats_pre_reset;
+
 -- End of Stats Test
-- 
2.34.1