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[PATCH v8 4/5] wip: report nanoseconds in pg_test_timing
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* [PATCH v8 4/5] wip: report nanoseconds in pg_test_timing
@ 2023-01-16 19:19  Andres Freund <[email protected]>
  0 siblings, 0 replies; 616+ 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 |  74 ++++++++------
 doc/src/sgml/ref/pgtesttiming.sgml      | 122 +++++++++++-------------
 2 files changed, 100 insertions(+), 96 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..e20718669a5 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[])
@@ -121,35 +121,48 @@ handle_args(int argc, char *argv[])
 static uint64
 test_timing(unsigned int duration)
 {
-	uint64		total_time;
-	int64		time_elapsed = 0;
 	uint64		loop_count = 0;
-	uint64		prev,
-				cur;
+	instr_time	until_time,
+				total_time;
 	instr_time	start_time,
-				end_time,
-				temp;
-
-	total_time = duration > 0 ? duration * INT64CONST(1000000) : 0;
+				end_time;
+	instr_time	cur;
 
 	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 (INSTR_TIME_IS_LT(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


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^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


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^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


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^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


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^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
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	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
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Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
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	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
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Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
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	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--jg9kqX3osLGO+8A7
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


--uN5gGi2rtCNSVbpC
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
Content-Type: text/x-diff; charset=us-ascii
Content-Disposition: attachment;
	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


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	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v5 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index 1441a051773..fe625d00f7d 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -261,6 +262,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 42bfb9cd38f..32ee48eab51 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -287,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 5d73c4dfbcf..780ca4b3ac0 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -525,6 +525,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -543,6 +544,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


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	filename="v5-0003-Adding-the-pg_stat_backend_transaction-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v3 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.

The counter is not part of PgStat_BackendPending, because we want to avoid
an extra function call in this code path to increment the counter in
PendingBackendStats. The counter increment here behaves more or less the same as
we do for WAL statistics.
---
 src/backend/access/transam/varsup.c         | 2 ++
 src/backend/utils/activity/pgstat_backend.c | 6 +++++-
 src/include/pgstat.h                        | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)
  10.1% src/backend/access/transam/
  69.3% src/backend/utils/activity/
  20.5% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index fe895787cb7..26c72cbe091 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -21,6 +21,7 @@
 #include "access/xlogutils.h"
 #include "commands/dbcommands.h"
 #include "miscadmin.h"
+#include "pgstat.h"
 #include "postmaster/autovacuum.h"
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
@@ -257,6 +258,7 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		XidGenCount++;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bf164854c4b..8b530c510b9 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -52,6 +52,8 @@ static WalUsage prevBackendWalUsage;
  */
 static bool backend_has_xactstats = false;
 
+PgStat_Counter XidGenCount = 0;
+
 /*
  * Utility routines to report I/O stats for backends, kept here to avoid
  * exposing PendingBackendStats to the outside world.
@@ -285,9 +287,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += XidGenCount;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	XidGenCount = 0;
 
 	backend_has_xactstats = false;
 }
@@ -317,7 +321,7 @@ pgstat_flush_backend(bool nowait, bits32 flags)
 		has_pending_data = true;
 
 	/* Some transaction data pending? */
-	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && backend_has_xactstats)
+	if ((flags & PGSTAT_BACKEND_FLUSH_XACT) && (backend_has_xactstats || XidGenCount > 0))
 		has_pending_data = true;
 
 	if (!has_pending_data)
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9efc0e10ebf..94dd24b3eac 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -571,6 +572,8 @@ extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);
 
+extern PGDLLIMPORT PgStat_Counter XidGenCount;
+
 /*
  * Functions in pgstat_bgwriter.c
  */
-- 
2.34.1


--u6+Li7FU79Mt/lVd
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	filename="v3-0003-Adding-the-pg_stat_backend-view.patch"



^ permalink  raw  reply  [nested|flat] 616+ messages in thread

* [PATCH v4 2/3] Adding XID generation count per backend
@ 2025-08-08 15:58  Bertrand Drouvot <[email protected]>
  0 siblings, 0 replies; 616+ messages in thread

From: Bertrand Drouvot @ 2025-08-08 15:58 UTC (permalink / raw)

This commit adds a new counter to record the number of XIDs generated per
backend. It will help to detect if a backend is consuming XIDs at a high rate.

Virtual transactions are not taken into account on purpose, we do want to track
only the XID where there is a risk of wraparound.
---
 src/backend/access/transam/varsup.c         | 4 ++++
 src/backend/utils/activity/pgstat_backend.c | 2 ++
 src/include/pgstat.h                        | 2 ++
 3 files changed, 8 insertions(+)
  43.8% src/backend/access/transam/
  36.6% src/backend/utils/activity/
  19.4% src/include/

diff --git a/src/backend/access/transam/varsup.c b/src/backend/access/transam/varsup.c
index f8c4dada7c9..72c8aa7650b 100644
--- a/src/backend/access/transam/varsup.c
+++ b/src/backend/access/transam/varsup.c
@@ -24,6 +24,7 @@
 #include "storage/pmsignal.h"
 #include "storage/proc.h"
 #include "utils/lsyscache.h"
+#include "utils/pgstat_internal.h"
 #include "utils/syscache.h"
 
 
@@ -257,6 +258,9 @@ GetNewTransactionId(bool isSubXact)
 		/* LWLockRelease acts as barrier */
 		MyProc->xid = xid;
 		ProcGlobal->xids[MyProc->pgxactoff] = xid;
+		PendingBackendStats.pending_xid_count++;
+		backend_has_xactstats = true;
+		pgstat_report_fixed = true;
 	}
 	else
 	{
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 47ce61e5093..5e509153656 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -285,9 +285,11 @@ pgstat_flush_backend_entry_xact(PgStat_EntryRef *entry_ref)
 
 	shbackendent->stats.xact_commit += PendingBackendStats.pending_xact_commit;
 	shbackendent->stats.xact_rollback += PendingBackendStats.pending_xact_rollback;
+	shbackendent->stats.xid_count += PendingBackendStats.pending_xid_count;
 
 	PendingBackendStats.pending_xact_commit = 0;
 	PendingBackendStats.pending_xact_rollback = 0;
+	PendingBackendStats.pending_xid_count = 0;
 
 	backend_has_xactstats = false;
 }
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 0fdbaf79780..d78633cae44 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -492,6 +492,7 @@ typedef struct PgStat_Backend
 	PgStat_WalCounters wal_counters;
 	PgStat_Counter xact_commit;
 	PgStat_Counter xact_rollback;
+	PgStat_Counter xid_count;
 } PgStat_Backend;
 
 /* ---------
@@ -510,6 +511,7 @@ typedef struct PgStat_BackendPending
 	 */
 	PgStat_Counter pending_xact_commit;
 	PgStat_Counter pending_xact_rollback;
+	PgStat_Counter pending_xid_count;
 } PgStat_BackendPending;
 
 /*
-- 
2.34.1


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	filename="v4-0003-Adding-the-pg_stat_backend_transaction-view.patch"



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