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[PATCH v7 4/4] wip: report nanoseconds in pg_test_timing
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* [PATCH v7 4/4] wip: report nanoseconds in pg_test_timing
@ 2023-01-16 19:19  Andres Freund <andres@anarazel.de>
  0 siblings, 0 replies; 325+ messages in thread

From: Andres Freund @ 2023-01-16 19:19 UTC (permalink / raw)

This commit also updates pg_test_timing's documentation:

- compare EXPLAIN (ANALYZE, TIMING ON/OFF) instead of comparing performance of
  of statement with/without EXPLAIN ANALYZE
- explain the 2x overhead (due to two timestamp acquisitions per row)
- remove old section about old versions of linux - I couldn't update the
  numbers, and it's old enough nobody would care
---
 src/bin/pg_test_timing/pg_test_timing.c |  72 ++++++++------
 doc/src/sgml/ref/pgtesttiming.sgml      | 122 +++++++++++-------------
 2 files changed, 99 insertions(+), 95 deletions(-)

diff --git a/src/bin/pg_test_timing/pg_test_timing.c b/src/bin/pg_test_timing/pg_test_timing.c
index c29d6f87629..bae10ce6fa4 100644
--- a/src/bin/pg_test_timing/pg_test_timing.c
+++ b/src/bin/pg_test_timing/pg_test_timing.c
@@ -19,8 +19,8 @@ static void handle_args(int argc, char *argv[]);
 static uint64 test_timing(unsigned int duration);
 static void output(uint64 loop_count);
 
-/* record duration in powers of 2 microseconds */
-long long int histogram[32];
+/* record duration in powers of 2 nanoseconds */
+uint64		histogram[64];
 
 int
 main(int argc, char *argv[])
@@ -122,34 +122,47 @@ static uint64
 test_timing(unsigned int duration)
 {
 	uint64		total_time;
-	int64		time_elapsed = 0;
 	uint64		loop_count = 0;
-	uint64		prev,
-				cur;
+	instr_time	cur;
 	instr_time	start_time,
-				end_time,
-				temp;
-
-	total_time = duration > 0 ? duration * INT64CONST(1000000) : 0;
+				end_time;
+	instr_time	until_time;
 
 	INSTR_TIME_SET_CURRENT(start_time);
-	cur = INSTR_TIME_GET_MICROSEC(start_time);
 
-	while (time_elapsed < total_time)
+	/*
+	 * To reduce loop overhead, check loop condition in instr_time domain.
+	 */
+	INSTR_TIME_SET_SECONDS(total_time, duration);
+	until_time = start_time;
+	INSTR_TIME_ADD(until_time, total_time);
+
+	cur = start_time;
+
+	while (cur < until_time)
 	{
-		int32		diff,
-					bits = 0;
+		instr_time	temp;
+		instr_time	prev;
+		int64		diff;
+		int32		bits = 0;
 
 		prev = cur;
-		INSTR_TIME_SET_CURRENT(temp);
-		cur = INSTR_TIME_GET_MICROSEC(temp);
-		diff = cur - prev;
+		INSTR_TIME_SET_CURRENT(cur);
+		temp = cur;
+		INSTR_TIME_SUBTRACT(temp, prev);
+		diff = INSTR_TIME_GET_NANOSEC(temp);
 
 		/* Did time go backwards? */
-		if (diff < 0)
+		if (unlikely(diff <= 0))
 		{
+			/* can't do anything with that measurement */
+			if (diff == 0)
+			{
+				loop_count++;
+				continue;
+			}
 			fprintf(stderr, _("Detected clock going backwards in time.\n"));
-			fprintf(stderr, _("Time warp: %d ms\n"), diff);
+			fprintf(stderr, _("Time warp: %lld ns\n"), (long long) diff);
 			exit(1);
 		}
 
@@ -164,8 +177,6 @@ test_timing(unsigned int duration)
 		histogram[bits]++;
 
 		loop_count++;
-		INSTR_TIME_SUBTRACT(temp, start_time);
-		time_elapsed = INSTR_TIME_GET_MICROSEC(temp);
 	}
 
 	INSTR_TIME_SET_CURRENT(end_time);
@@ -173,7 +184,7 @@ test_timing(unsigned int duration)
 	INSTR_TIME_SUBTRACT(end_time, start_time);
 
 	printf(_("Per loop time including overhead: %0.2f ns\n"),
-		   INSTR_TIME_GET_DOUBLE(end_time) * 1e9 / loop_count);
+		   (INSTR_TIME_GET_DOUBLE(end_time) * NS_PER_S) / loop_count);
 
 	return loop_count;
 }
@@ -181,9 +192,10 @@ test_timing(unsigned int duration)
 static void
 output(uint64 loop_count)
 {
-	int64		max_bit = 31,
+	int64		low_bit = 0,
+				max_bit = 63,
 				i;
-	char	   *header1 = _("< us");
+	char	   *header1 = _("< ns");
 	char	   *header2 = /* xgettext:no-c-format */ _("% of total");
 	char	   *header3 = _("count");
 	int			len1 = strlen(header1);
@@ -194,15 +206,19 @@ output(uint64 loop_count)
 	while (max_bit > 0 && histogram[max_bit] == 0)
 		max_bit--;
 
+	/* find lowest bit value */
+	while (low_bit < max_bit && histogram[low_bit] == 0)
+		low_bit++;
+
 	printf(_("Histogram of timing durations:\n"));
 	printf("%*s   %*s %*s\n",
-		   Max(6, len1), header1,
+		   Max(9, len1), header1,
 		   Max(10, len2), header2,
 		   Max(10, len3), header3);
 
-	for (i = 0; i <= max_bit; i++)
-		printf("%*ld    %*.5f %*lld\n",
-			   Max(6, len1), 1l << i,
+	for (i = low_bit; i <= max_bit; i++)
+		printf("%*ld    %*.5f %*llu\n",
+			   Max(9, len1), 1l << i,
 			   Max(10, len2) - 1, (double) histogram[i] * 100 / loop_count,
-			   Max(10, len3), histogram[i]);
+			   Max(10, len3), (long long unsigned) histogram[i]);
 }
diff --git a/doc/src/sgml/ref/pgtesttiming.sgml b/doc/src/sgml/ref/pgtesttiming.sgml
index a5eb3aa25e0..82c625e3a2a 100644
--- a/doc/src/sgml/ref/pgtesttiming.sgml
+++ b/doc/src/sgml/ref/pgtesttiming.sgml
@@ -93,28 +93,34 @@ PostgreSQL documentation
 
   <para>
    Good results will show most (>90%) individual timing calls take less than
-   one microsecond. Average per loop overhead will be even lower, below 100
-   nanoseconds. This example from an Intel i7-860 system using a TSC clock
-   source shows excellent performance:
+   one microsecond (1000 nanoseconds). Average per loop overhead will be even
+   lower, below 100 nanoseconds. This example from an Intel i9-9880H system
+   using a TSC clock source shows excellent performance:
 
 <screen><![CDATA[
 Testing timing overhead for 3 seconds.
-Per loop time including overhead: 35.96 ns
+Per loop time including overhead: 13.74 ns
 Histogram of timing durations:
-  < us   % of total      count
-     1     96.40465   80435604
-     2      3.59518    2999652
-     4      0.00015        126
-     8      0.00002         13
-    16      0.00000          2
+     < ns   % of total      count
+       16     97.00221  211857215
+       32      2.99555    6542412
+       64      0.00115       2505
+      128      0.00035        759
+      256      0.00004         78
+      512      0.00000          3
+     1024      0.00000          4
+     2048      0.00034        732
+     4096      0.00000          6
+     8192      0.00000          8
+    16384      0.00019        409
+    32768      0.00018        403
+    65536      0.00000          1
 ]]></screen>
   </para>
 
   <para>
-   Note that different units are used for the per loop time than the
-   histogram. The loop can have resolution within a few nanoseconds (ns),
-   while the individual timing calls can only resolve down to one microsecond
-   (us).
+   Note that the accuracy of the histogram entries may be lower than the
+   per loop time.
   </para>
 
  </refsect2>
@@ -125,24 +131,30 @@ Histogram of timing durations:
    When the query executor is running a statement using
    <command>EXPLAIN ANALYZE</command>, individual operations are timed as well
    as showing a summary.  The overhead of your system can be checked by
-   counting rows with the <application>psql</application> program:
+   disabling the per-row timing, using the <literal>TIMING OFF</literal>
+   option:
 
 <screen>
-CREATE TABLE t AS SELECT * FROM generate_series(1,100000);
-\timing
-SELECT COUNT(*) FROM t;
-EXPLAIN ANALYZE SELECT COUNT(*) FROM t;
+CREATE TABLE t AS SELECT * FROM generate_series(1, 100000);
+EXPLAIN (ANALYZE, TIMING OFF) SELECT COUNT(*) FROM t;
+EXPLAIN (ANALYZE, TIMING ON) SELECT COUNT(*) FROM t;
 </screen>
   </para>
 
   <para>
-   The i7-860 system measured runs the count query in 9.8 ms while
-   the <command>EXPLAIN ANALYZE</command> version takes 16.6 ms, each
-   processing just over 100,000 rows.  That 6.8 ms difference means the timing
-   overhead per row is 68 ns, about twice what pg_test_timing estimated it
-   would be.  Even that relatively small amount of overhead is making the fully
-   timed count statement take almost 70% longer.  On more substantial queries,
-   the timing overhead would be less problematic.
+   The i9-9880H system measured shows an execution time of 4.116 ms for the
+   <literal>TIMING OFF</literal> query, and 6.965 ms for the
+   <literal>TIMING ON</literal>, each processing 100,000 rows.
+
+   That 2.849 ms difference means the timing overhead per row is 28 ns.  As
+   <literal>TIMING ON</literal> measures timestamps twice per row returned by
+   an executor node, the overhead is very close to what pg_test_timing
+   estimated it would be.
+
+   more than what pg_test_timing estimated it would be.  Even that relatively
+   small amount of overhead is making the fully timed count statement take
+   about 60% longer.  On more substantial queries, the timing overhead would
+   be less problematic.
   </para>
 
  </refsect2>
@@ -157,28 +169,31 @@ EXPLAIN ANALYZE SELECT COUNT(*) FROM t;
 
 <screen><![CDATA[
 # cat /sys/devices/system/clocksource/clocksource0/available_clocksource
-tsc hpet acpi_pm
+tsc acpi_pm
 # echo acpi_pm > /sys/devices/system/clocksource/clocksource0/current_clocksource
 # pg_test_timing
-Per loop time including overhead: 722.92 ns
+Testing timing overhead for 3 seconds.
+Per loop time including overhead: 708.58 ns
 Histogram of timing durations:
-  < us   % of total      count
-     1     27.84870    1155682
-     2     72.05956    2990371
-     4      0.07810       3241
-     8      0.01357        563
-    16      0.00007          3
+     < ns   % of total      count
+     1024     99.79796    4225270
+     2048      0.15560       6588
+     4096      0.00035         15
+     8192      0.01738        736
+    16384      0.01679        711
+    32768      0.01190        504
 ]]></screen>
   </para>
 
   <para>
    In this configuration, the sample <command>EXPLAIN ANALYZE</command> above
-   takes 115.9 ms.  That's 1061 ns of timing overhead, again a small multiple
-   of what's measured directly by this utility.  That much timing overhead
-   means the actual query itself is only taking a tiny fraction of the
-   accounted for time, most of it is being consumed in overhead instead.  In
-   this configuration, any <command>EXPLAIN ANALYZE</command> totals involving
-   many timed operations would be inflated significantly by timing overhead.
+   shows an execution time of 148.7 ms.  That's 1392 ns of timing overhead,
+   again a small multiple of what's measured directly by this utility.  That
+   much timing overhead means the actual query itself is only taking a tiny
+   fraction of the accounted for time, most of it is being consumed in
+   overhead instead.  In this configuration, any <command>EXPLAIN
+   ANALYZE</command> totals involving many timed operations would be inflated
+   significantly by timing overhead.
   </para>
 
   <para>
@@ -196,33 +211,6 @@ kern.timecounter.hardware: ACPI-fast -> TSC
 </screen>
   </para>
 
-  <para>
-   Other systems may only allow setting the time source on boot.  On older
-   Linux systems the "clock" kernel setting is the only way to make this sort
-   of change.  And even on some more recent ones, the only option you'll see
-   for a clock source is "jiffies".  Jiffies are the older Linux software clock
-   implementation, which can have good resolution when it's backed by fast
-   enough timing hardware, as in this example:
-
-<screen><![CDATA[
-$ cat /sys/devices/system/clocksource/clocksource0/available_clocksource
-jiffies
-$ dmesg | grep time.c
-time.c: Using 3.579545 MHz WALL PM GTOD PIT/TSC timer.
-time.c: Detected 2400.153 MHz processor.
-$ pg_test_timing
-Testing timing overhead for 3 seconds.
-Per timing duration including loop overhead: 97.75 ns
-Histogram of timing durations:
-  < us   % of total      count
-     1     90.23734   27694571
-     2      9.75277    2993204
-     4      0.00981       3010
-     8      0.00007         22
-    16      0.00000          1
-    32      0.00000          1
-]]></screen></para>
-
  </refsect2>
 
  <refsect2>
-- 
2.38.0


--ftp5i6iirmkwy7na--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v3 3/3] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of XIDs generated, the number of commits, the number of rollbacks and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 115 +++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |   9 +++
 src/backend/utils/adt/pgstatfuncs.c  |  57 +++++++++++++
 src/include/catalog/pg_proc.dat      |   9 +++
 src/test/regress/expected/rules.out  |   6 ++
 src/test/regress/expected/stats.out  |  17 ++++
 src/test/regress/sql/stats.sql       |  10 +++
 7 files changed, 223 insertions(+)
  51.1% doc/src/sgml/
   3.2% src/backend/catalog/
  23.9% src/backend/utils/adt/
   7.2% src/include/catalog/
   9.4% src/test/regress/expected/
   4.9% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..0146c812b40 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,20 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of commits and
+       rollbacks.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1186,91 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xid_count</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of XID that have been generated by the backend. It does not take
+       into account virtual transaction ID on purpose.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_commit</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been committed.
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>xact_rollback</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of transactions that have been rolled back.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5020,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..96a1a556773 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,15 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.xid_count,
+            S.xact_commit,
+            S.xact_rollback,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..dcb20009bec 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,63 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	5
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->xid_count);
+		values[2] = Int64GetDatum(backend_stats->xact_commit);
+		values[3] = Int64GetDatum(backend_stats->xact_rollback);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[4] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[4] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..dc0c0db6358 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,int8,int8,timestamptz}',
+  proargmodes => '{i,o,o,o,o,o}',
+  proargnames => '{pid,pid,xid_count,xact_commit,xact_rollback,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..a107f6ca44d 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,12 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    xid_count,
+    xact_commit,
+    xact_rollback,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, xid_count, xact_commit, xact_rollback, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..a4b6d27c31d 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -135,11 +135,28 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush 
+--------------------------
+ 
+(1 row)
+
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :xact_commit_after > :xact_commit_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..f25368d1d25 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -58,12 +58,22 @@ INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 UPDATE trunc_stats_test1 SET id = id + 10 WHERE id IN (1, 2);
 DELETE FROM trunc_stats_test1 WHERE id = 3;
 
+-- in passing, check that backend's commit is incrementing
+SELECT xact_commit AS xact_commit_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 BEGIN;
 UPDATE trunc_stats_test1 SET id = id + 100;
 TRUNCATE trunc_stats_test1;
 INSERT INTO trunc_stats_test1 DEFAULT VALUES;
 COMMIT;
 
+SELECT pg_stat_force_next_flush();
+SELECT xact_commit AS xact_commit_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :xact_commit_after > :xact_commit_before;
+
 -- use a savepoint: 1 insert, 1 live
 BEGIN;
 INSERT INTO trunc_stats_test2 DEFAULT VALUES;
-- 
2.34.1


--u6+Li7FU79Mt/lVd--





^ permalink  raw  reply  [nested|flat] 325+ messages in thread

* [PATCH v1 02/10] Adding the pg_stat_backend view
@ 2025-08-09 14:22  Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
  0 siblings, 0 replies; 325+ messages in thread

From: Bertrand Drouvot @ 2025-08-09 14:22 UTC (permalink / raw)

This view displays one row per server process, showing statistics related to
the current activity of that process. It currently displays the pid, the
number of sequential scans initiated on tables and the
time at which these statistics were last reset.

It's built on top of a new function (pg_stat_get_backend_statistics()). The idea
is the same as pg_stat_activity and pg_stat_get_activity().

Adding documentation and tests.

XXX: Bump catversion
---
 doc/src/sgml/monitoring.sgml         | 95 ++++++++++++++++++++++++++++
 src/backend/catalog/system_views.sql |  7 ++
 src/backend/utils/adt/pgstatfuncs.c  | 55 ++++++++++++++++
 src/include/catalog/pg_proc.dat      |  9 +++
 src/test/regress/expected/rules.out  |  4 ++
 src/test/regress/expected/stats.out  | 10 +++
 src/test/regress/sql/stats.sql       |  8 +++
 7 files changed, 188 insertions(+)
  50.8% doc/src/sgml/
  26.9% src/backend/utils/adt/
   8.0% src/include/catalog/
   7.1% src/test/regress/expected/
   4.0% src/test/regress/sql/

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 3f4a27a736e..6868af55db4 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -320,6 +320,19 @@ postgres   27093  0.0  0.0  30096  2752 ?        Ss   11:34   0:00 postgres: ser
       </entry>
      </row>
 
+     <row>
+      <entry>
+       <structname>pg_stat_backend</structname>
+       <indexterm><primary>pg_stat_backend</primary></indexterm>
+      </entry>
+      <entry>
+       One row per server process, showing statistics related to
+       the current activity of that process, such as number of sequential scans.
+       See <link linkend="monitoring-pg-stat-backend-view">
+       <structname>pg_stat_backend</structname></link> for details.
+      </entry>
+     </row>
+
      <row>
       <entry><structname>pg_stat_replication</structname><indexterm><primary>pg_stat_replication</primary></indexterm></entry>
       <entry>One row per WAL sender process, showing statistics about
@@ -1172,6 +1185,72 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    </note>
  </sect2>
 
+ <sect2 id="monitoring-pg-stat-backend-view">
+  <title><structname>pg_stat_backend</structname></title>
+
+  <indexterm>
+   <primary>pg_stat_backend</primary>
+  </indexterm>
+
+  <para>
+   The <structname>pg_stat_backend</structname> view will have one row
+   per server process, showing statistics related to
+   the current activity of that process.
+  </para>
+
+  <table id="pg-stat-backend-view" xreflabel="pg_stat_backend">
+   <title><structname>pg_stat_backend</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>pid</structfield> <type>integer</type>
+      </para>
+      <para>
+       Process ID of this backend
+      </para></entry>
+     </row>
+
+     <row>
+      <entry role="catalog_table_entry"><para role="column_definition">
+       <structfield>seq_scan</structfield> <type>bigint</type>
+      </para>
+      <para>
+       The number of sequential scans initiated on tables.
+      </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>
+   </tgroup>
+  </table>
+
+  <note>
+   <para>
+    The view does not return statistics for the checkpointer,
+    the background writer, the startup process and the autovacuum launcher.
+   </para>
+  </note>
+ </sect2>
+
  <sect2 id="monitoring-pg-stat-replication-view">
   <title><structname>pg_stat_replication</structname></title>
 
@@ -4921,6 +5000,22 @@ description | Waiting for a newly initialized WAL file to reach durable storage
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_stat_get_backend_statistics</primary>
+        </indexterm>
+        <function>pg_stat_get_backend_statistics</function> ( <type>integer</type> )
+        <returnvalue>setof record</returnvalue>
+       </para>
+       <para>
+        Returns a record of statistics bout the backend with the specified
+        process ID, or one record for each active backend in the system
+        if <literal>NULL</literal> is specified.  The fields returned are a
+        subset of those in the <structname>pg_stat_backend</structname> view.
+       </para></entry>
+      </row>
+
       <row>
        <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index 1b3c5a55882..3ab7802cc5c 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -911,6 +911,13 @@ CREATE VIEW pg_stat_activity AS
         LEFT JOIN pg_database AS D ON (S.datid = D.oid)
         LEFT JOIN pg_authid AS U ON (S.usesysid = U.oid);
 
+CREATE VIEW pg_stat_backend AS
+    SELECT
+            S.pid,
+            S.seq_scan,
+            S.stats_reset
+    FROM pg_stat_get_backend_statistics(NULL) AS S;
+
 CREATE VIEW pg_stat_replication AS
     SELECT
             S.pid,
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index c756c2bebaa..2adfbdcb65c 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -685,6 +685,61 @@ pg_stat_get_activity(PG_FUNCTION_ARGS)
 	return (Datum) 0;
 }
 
+/*
+ * Returns statistics of PG backends.
+ */
+Datum
+pg_stat_get_backend_statistics(PG_FUNCTION_ARGS)
+{
+#define PG_STAT_GET_BACKEND_STATS_COLS	3
+	int			num_backends = pgstat_fetch_stat_numbackends();
+	int			curr_backend;
+	int			pid = PG_ARGISNULL(0) ? -1 : PG_GETARG_INT32(0);
+	ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
+
+	InitMaterializedSRF(fcinfo, 0);
+
+	/* 1-based index */
+	for (curr_backend = 1; curr_backend <= num_backends; curr_backend++)
+	{
+		/* for each row */
+		Datum		values[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		bool		nulls[PG_STAT_GET_BACKEND_STATS_COLS] = {0};
+		LocalPgBackendStatus *local_beentry;
+		PgBackendStatus *beentry;
+		PgStat_Backend *backend_stats;
+
+		/* Get the next one in the list */
+		local_beentry = pgstat_get_local_beentry_by_index(curr_backend);
+		beentry = &local_beentry->backendStatus;
+
+		/* If looking for specific PID, ignore all the others */
+		if (pid != -1 && beentry->st_procpid != pid)
+			continue;
+
+		backend_stats = pgstat_fetch_stat_backend_by_pid(beentry->st_procpid, NULL);
+
+		values[0] = Int32GetDatum(beentry->st_procpid);
+
+		if (!backend_stats)
+			continue;
+
+		values[1] = Int64GetDatum(backend_stats->heap_scan);
+
+		if (backend_stats->stat_reset_timestamp != 0)
+			values[2] = TimestampTzGetDatum(backend_stats->stat_reset_timestamp);
+		else
+			nulls[2] = true;
+
+		tuplestore_putvalues(rsinfo->setResult, rsinfo->setDesc, values, nulls);
+
+		/* If only a single backend was requested, and we found it, break. */
+		if (pid != -1)
+			break;
+	}
+
+	return (Datum) 0;
+}
 
 Datum
 pg_backend_pid(PG_FUNCTION_ARGS)
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 118d6da1ace..e87200374d8 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5641,6 +5641,15 @@
   proargmodes => '{i,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o,o}',
   proargnames => '{pid,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,gss_delegation,leader_pid,query_id}',
   prosrc => 'pg_stat_get_activity' },
+{ oid => '9555',
+  descr => 'statistics: statistics about currently active backends',
+  proname => 'pg_stat_get_backend_statistics', prorows => '100', proisstrict => 'f',
+  proretset => 't', provolatile => 's', proparallel => 'r',
+  prorettype => 'record', proargtypes => 'int4',
+  proallargtypes => '{int4,int4,int8,timestamptz}',
+  proargmodes => '{i,o,o,o}',
+  proargnames => '{pid,pid,seq_scan,stats_reset}',
+  prosrc => 'pg_stat_get_backend_statistics' },
 { oid => '6318', descr => 'describe wait events',
   proname => 'pg_get_wait_events', procost => '10', prorows => '250',
   proretset => 't', provolatile => 'v', prorettype => 'record',
diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out
index 35e8aad7701..63f8f12b8a5 100644
--- a/src/test/regress/expected/rules.out
+++ b/src/test/regress/expected/rules.out
@@ -1847,6 +1847,10 @@ pg_stat_archiver| SELECT archived_count,
     last_failed_time,
     stats_reset
    FROM pg_stat_get_archiver() s(archived_count, last_archived_wal, last_archived_time, failed_count, last_failed_wal, last_failed_time, stats_reset);
+pg_stat_backend| SELECT pid,
+    seq_scan,
+    stats_reset
+   FROM pg_stat_get_backend_statistics(NULL::integer) s(pid, seq_scan, stats_reset);
 pg_stat_bgwriter| SELECT pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
     pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
     pg_stat_get_buf_alloc() AS buffers_alloc,
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index 605f5070376..937bf4bfc5b 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -118,6 +118,8 @@ SELECT t.seq_scan, t.seq_tup_read, t.idx_scan, t.idx_tup_fetch,
        pg_catalog.pg_statio_user_tables AS b
  WHERE t.relname='tenk2' AND b.relname='tenk2';
 COMMIT;
+SELECT seq_scan AS seq_scan_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
 -- test effects of TRUNCATE on n_live_tup/n_dead_tup counters
 CREATE TABLE trunc_stats_test(id serial);
 CREATE TABLE trunc_stats_test1(id serial, stuff text);
@@ -219,6 +221,14 @@ SELECT st.seq_scan >= pr.seq_scan + 1,
  t        | t        | t        | t
 (1 row)
 
+SELECT seq_scan AS seq_scan_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+SELECT :seq_scan_after > :seq_scan_before;
+ ?column? 
+----------
+ t
+(1 row)
+
 SELECT st.heap_blks_read + st.heap_blks_hit >= pr.heap_blks + cl.relpages,
        st.idx_blks_read + st.idx_blks_hit >= pr.idx_blks + 1
   FROM pg_statio_user_tables AS st, pg_class AS cl, prevstats AS pr
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 54e72866344..b743352eadb 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -38,6 +38,9 @@ SELECT t.seq_scan, t.seq_tup_read, t.idx_scan, t.idx_tup_fetch,
  WHERE t.relname='tenk2' AND b.relname='tenk2';
 COMMIT;
 
+SELECT seq_scan AS seq_scan_before
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
 -- test effects of TRUNCATE on n_live_tup/n_dead_tup counters
 CREATE TABLE trunc_stats_test(id serial);
 CREATE TABLE trunc_stats_test1(id serial, stuff text);
@@ -122,6 +125,11 @@ SELECT st.seq_scan >= pr.seq_scan + 1,
   FROM pg_stat_user_tables AS st, pg_class AS cl, prevstats AS pr
  WHERE st.relname='tenk2' AND cl.relname='tenk2';
 
+SELECT seq_scan AS seq_scan_after
+  FROM pg_stat_backend WHERE pid = pg_backend_pid() \gset
+
+SELECT :seq_scan_after > :seq_scan_before;
+
 SELECT st.heap_blks_read + st.heap_blks_hit >= pr.heap_blks + cl.relpages,
        st.idx_blks_read + st.idx_blks_hit >= pr.idx_blks + 1
   FROM pg_statio_user_tables AS st, pg_class AS cl, prevstats AS pr
-- 
2.34.1


--j6dXQ8GCuNzKPBpX
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v1-0003-Adding-seq_tup_read-to-pg_stat_backend.patch"



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