Hi,
On Fri, Jan 17, 2025 at 08:43:57AM +0900, Michael Paquier wrote:
> On Thu, Jan 16, 2025 at 12:44:20PM -0500, Andres Freund wrote:
> > On 2025-01-16 17:11:09 +0000, Bertrand Drouvot wrote:
> >> So, do you think that the initial proposal that has been made here (See
> >> R1. in
> >> [2]) i.e make use of a new PendingBackendWalStats variable:
> >
> > Well, I think this first needs be fixed for for the IO stats change made in
> >
> > Once we have a pattern to model after, we can apply the same scheme here.
>
> Okay, thanks for the input. I was not sure what you intended
> originally with all this part of the backend code, and how much would
> be acceptable. The line is clear now.
>
> >> 0003 does not rely on pgstat_prep_backend_pending() for its pending
> >> statistics
> >> but on a new PendingBackendWalStats variable. The reason is that the
> >> pending wal
> >> statistics are incremented in a critical section (see XLogWrite(), and so
> >> a call to pgstat_prep_pending_entry() could trigger a failed assertion:
> >> MemoryContextAllocZero()->"CritSectionCount == 0 ||
> >> (context)->allowInCritSection"
> >> "
> >>
> >> and implemented up to v4 is a viable approach?
> >
> > Yes-ish. I think it would be better to make it slightly more general than
> > that, handling this for all types of backend stats, not just for WAL.
>
> Agreed to use the same concept for all these parts of the backend
> stats kind rather than two of them. Will send a reply on the original
> backend I/O thread as well.
PFA v6 that now relies on the new PendingBackendStats variable introduced in
4feba03d8b9.
Remark: I moved PendingBackendStats back to pgstat.h because I think that the
"simple" pending stats increment that we are adding in xlog.c are not worth
an extra function call overhead (while it made more sense for the more complex
IO
stats handling). So PendingBackendStats is now visible to the outside world like
PendingWalStats and friends.
Regards,
--
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
>From 4f2a197b086dd64a2723a8491cc66453012743e9 Mon Sep 17 00:00:00 2001
From: Bertrand Drouvot <bertranddrouvot...@gmail.com>
Date: Mon, 6 Jan 2025 07:51:27 +0000
Subject: [PATCH v6 1/3] Extract logic filling pg_stat_get_wal()'s tuple into
its own routine
This commit adds pg_stat_wal_build_tuple(), a helper routine for
pg_stat_get_wal(), that fills its tuple based on the contents
of PgStat_WalStats. This will be used in a follow-up commit that uses
the same structures as pg_stat_wal for reporting, but for the PGSTAT_KIND_BACKEND
statistics kind.
---
src/backend/utils/adt/pgstatfuncs.c | 56 ++++++++++++++++++-----------
1 file changed, 36 insertions(+), 20 deletions(-)
100.0% src/backend/utils/adt/
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 0f5e0a9778d..0442be03304 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1604,20 +1604,22 @@ pg_stat_get_backend_io(PG_FUNCTION_ARGS)
}
/*
- * Returns statistics of WAL activity
+ * pg_stat_wal_build_tuple
+ *
+ * Helper routine for pg_stat_get_wal() returning one tuple based on the contents
+ * of wal_stats.
*/
-Datum
-pg_stat_get_wal(PG_FUNCTION_ARGS)
+static Datum
+pg_stat_wal_build_tuple(PgStat_WalStats wal_stats)
{
-#define PG_STAT_GET_WAL_COLS 9
+#define PG_STAT_WAL_COLS 9
TupleDesc tupdesc;
- Datum values[PG_STAT_GET_WAL_COLS] = {0};
- bool nulls[PG_STAT_GET_WAL_COLS] = {0};
+ Datum values[PG_STAT_WAL_COLS] = {0};
+ bool nulls[PG_STAT_WAL_COLS] = {0};
char buf[256];
- PgStat_WalStats *wal_stats;
/* Initialise attributes information in the tuple descriptor */
- tupdesc = CreateTemplateTupleDesc(PG_STAT_GET_WAL_COLS);
+ tupdesc = CreateTemplateTupleDesc(PG_STAT_WAL_COLS);
TupleDescInitEntry(tupdesc, (AttrNumber) 1, "wal_records",
INT8OID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 2, "wal_fpi",
@@ -1639,34 +1641,48 @@ pg_stat_get_wal(PG_FUNCTION_ARGS)
BlessTupleDesc(tupdesc);
- /* Get statistics about WAL activity */
- wal_stats = pgstat_fetch_stat_wal();
-
/* Fill values and NULLs */
- values[0] = Int64GetDatum(wal_stats->wal_records);
- values[1] = Int64GetDatum(wal_stats->wal_fpi);
+ values[0] = Int64GetDatum(wal_stats.wal_records);
+ values[1] = Int64GetDatum(wal_stats.wal_fpi);
/* Convert to numeric. */
- snprintf(buf, sizeof buf, UINT64_FORMAT, wal_stats->wal_bytes);
+ snprintf(buf, sizeof buf, UINT64_FORMAT, wal_stats.wal_bytes);
values[2] = DirectFunctionCall3(numeric_in,
CStringGetDatum(buf),
ObjectIdGetDatum(0),
Int32GetDatum(-1));
- values[3] = Int64GetDatum(wal_stats->wal_buffers_full);
- values[4] = Int64GetDatum(wal_stats->wal_write);
- values[5] = Int64GetDatum(wal_stats->wal_sync);
+ values[3] = Int64GetDatum(wal_stats.wal_buffers_full);
+ values[4] = Int64GetDatum(wal_stats.wal_write);
+ values[5] = Int64GetDatum(wal_stats.wal_sync);
/* Convert counters from microsec to millisec for display */
- values[6] = Float8GetDatum(((double) wal_stats->wal_write_time) / 1000.0);
- values[7] = Float8GetDatum(((double) wal_stats->wal_sync_time) / 1000.0);
+ values[6] = Float8GetDatum(((double) wal_stats.wal_write_time) / 1000.0);
+ values[7] = Float8GetDatum(((double) wal_stats.wal_sync_time) / 1000.0);
- values[8] = TimestampTzGetDatum(wal_stats->stat_reset_timestamp);
+ if (wal_stats.stat_reset_timestamp != 0)
+ values[8] = TimestampTzGetDatum(wal_stats.stat_reset_timestamp);
+ else
+ nulls[8] = true;
/* Returns the record as Datum */
PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
}
+/*
+ * Returns statistics of WAL activity
+ */
+Datum
+pg_stat_get_wal(PG_FUNCTION_ARGS)
+{
+ PgStat_WalStats *wal_stats;
+
+ /* Get statistics about WAL activity */
+ wal_stats = pgstat_fetch_stat_wal();
+
+ return (pg_stat_wal_build_tuple(*wal_stats));
+}
+
/*
* Returns statistics of SLRU caches.
*/
--
2.34.1
>From 49b4d7f60c30dfa53d7994b05ce012782f449190 Mon Sep 17 00:00:00 2001
From: Bertrand Drouvot <bertranddrouvot...@gmail.com>
Date: Thu, 16 Jan 2025 15:06:01 +0000
Subject: [PATCH v6 2/3] Adding a new PgStat_WalCounters struct
This new struct contains only the counters related to the WAL statistics.
This will be used in a follow-up commit that uses the same structures but
for the PGSTAT_KIND_BACKEND statistics kind.
---
src/backend/utils/activity/pgstat_wal.c | 4 ++--
src/backend/utils/adt/pgstatfuncs.c | 28 +++++++++++++------------
src/include/pgstat.h | 7 ++++++-
src/tools/pgindent/typedefs.list | 1 +
4 files changed, 24 insertions(+), 16 deletions(-)
14.1% src/backend/utils/activity/
79.8% src/backend/utils/adt/
5.0% src/include/
diff --git a/src/backend/utils/activity/pgstat_wal.c b/src/backend/utils/activity/pgstat_wal.c
index 18fa6b2936a..bfc06178a68 100644
--- a/src/backend/utils/activity/pgstat_wal.c
+++ b/src/backend/utils/activity/pgstat_wal.c
@@ -117,9 +117,9 @@ pgstat_wal_flush_cb(bool nowait)
return true;
#define WALSTAT_ACC(fld, var_to_add) \
- (stats_shmem->stats.fld += var_to_add.fld)
+ (stats_shmem->stats.wal_counters.fld += var_to_add.fld)
#define WALSTAT_ACC_INSTR_TIME(fld) \
- (stats_shmem->stats.fld += INSTR_TIME_GET_MICROSEC(PendingWalStats.fld))
+ (stats_shmem->stats.wal_counters.fld += INSTR_TIME_GET_MICROSEC(PendingWalStats.fld))
WALSTAT_ACC(wal_records, wal_usage_diff);
WALSTAT_ACC(wal_fpi, wal_usage_diff);
WALSTAT_ACC(wal_bytes, wal_usage_diff);
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 0442be03304..97510d48eef 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1607,10 +1607,11 @@ pg_stat_get_backend_io(PG_FUNCTION_ARGS)
* pg_stat_wal_build_tuple
*
* Helper routine for pg_stat_get_wal() returning one tuple based on the contents
- * of wal_stats.
+ * of wal_counters.
*/
static Datum
-pg_stat_wal_build_tuple(PgStat_WalStats wal_stats)
+pg_stat_wal_build_tuple(PgStat_WalCounters wal_counters,
+ TimestampTz stat_reset_timestamp)
{
#define PG_STAT_WAL_COLS 9
TupleDesc tupdesc;
@@ -1642,26 +1643,26 @@ pg_stat_wal_build_tuple(PgStat_WalStats wal_stats)
BlessTupleDesc(tupdesc);
/* Fill values and NULLs */
- values[0] = Int64GetDatum(wal_stats.wal_records);
- values[1] = Int64GetDatum(wal_stats.wal_fpi);
+ values[0] = Int64GetDatum(wal_counters.wal_records);
+ values[1] = Int64GetDatum(wal_counters.wal_fpi);
/* Convert to numeric. */
- snprintf(buf, sizeof buf, UINT64_FORMAT, wal_stats.wal_bytes);
+ snprintf(buf, sizeof buf, UINT64_FORMAT, wal_counters.wal_bytes);
values[2] = DirectFunctionCall3(numeric_in,
CStringGetDatum(buf),
ObjectIdGetDatum(0),
Int32GetDatum(-1));
- values[3] = Int64GetDatum(wal_stats.wal_buffers_full);
- values[4] = Int64GetDatum(wal_stats.wal_write);
- values[5] = Int64GetDatum(wal_stats.wal_sync);
+ values[3] = Int64GetDatum(wal_counters.wal_buffers_full);
+ values[4] = Int64GetDatum(wal_counters.wal_write);
+ values[5] = Int64GetDatum(wal_counters.wal_sync);
/* Convert counters from microsec to millisec for display */
- values[6] = Float8GetDatum(((double) wal_stats.wal_write_time) / 1000.0);
- values[7] = Float8GetDatum(((double) wal_stats.wal_sync_time) / 1000.0);
+ values[6] = Float8GetDatum(((double) wal_counters.wal_write_time) / 1000.0);
+ values[7] = Float8GetDatum(((double) wal_counters.wal_sync_time) / 1000.0);
- if (wal_stats.stat_reset_timestamp != 0)
- values[8] = TimestampTzGetDatum(wal_stats.stat_reset_timestamp);
+ if (stat_reset_timestamp != 0)
+ values[8] = TimestampTzGetDatum(stat_reset_timestamp);
else
nulls[8] = true;
@@ -1680,7 +1681,8 @@ pg_stat_get_wal(PG_FUNCTION_ARGS)
/* Get statistics about WAL activity */
wal_stats = pgstat_fetch_stat_wal();
- return (pg_stat_wal_build_tuple(*wal_stats));
+ return (pg_stat_wal_build_tuple(wal_stats->wal_counters,
+ wal_stats->stat_reset_timestamp));
}
/*
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index d0d45150977..9bbba883685 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -467,7 +467,7 @@ typedef struct PgStat_StatTabEntry
PgStat_Counter autoanalyze_count;
} PgStat_StatTabEntry;
-typedef struct PgStat_WalStats
+typedef struct PgStat_WalCounters
{
PgStat_Counter wal_records;
PgStat_Counter wal_fpi;
@@ -477,6 +477,11 @@ typedef struct PgStat_WalStats
PgStat_Counter wal_sync;
PgStat_Counter wal_write_time;
PgStat_Counter wal_sync_time;
+} PgStat_WalCounters;
+
+typedef struct PgStat_WalStats
+{
+ PgStat_WalCounters wal_counters;
TimestampTz stat_reset_timestamp;
} PgStat_WalStats;
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index d5aa5c295ae..d752e626cb0 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -2178,6 +2178,7 @@ PgStat_SubXactStatus
PgStat_TableCounts
PgStat_TableStatus
PgStat_TableXactStatus
+PgStat_WalCounters
PgStat_WalStats
PgXmlErrorContext
PgXmlStrictness
--
2.34.1
>From c00c545ed8da5c37d5590018df30b633b32b2ed7 Mon Sep 17 00:00:00 2001
From: Bertrand Drouvot <bertranddrouvot...@gmail.com>
Date: Mon, 6 Jan 2025 10:00:00 +0000
Subject: [PATCH v6 3/3] per backend WAL statistics
Now that commit 9aea73fc61 added backend-level statistics to pgstats (and
per backend IO statistics) we can more easily add per backend statistics.
This commit adds per backend WAL statistics using the same layer as pg_stat_wal,
except that it is now possible to know how much WAL activity is happening in each
backend rather than an overall aggregate of all the activity. A function called
pg_stat_get_backend_wal() is added to access this data depending on the
PID of a backend.
The same limitation as in 9aea73fc61 persists, meaning that Auxiliary processes
are not included in this set of statistics.
XXX: bump catalog version
---
doc/src/sgml/config.sgml | 4 +-
doc/src/sgml/monitoring.sgml | 19 +++++
src/backend/access/transam/xlog.c | 35 +++++++-
src/backend/utils/activity/pgstat_backend.c | 91 ++++++++++++++++++++-
src/backend/utils/activity/pgstat_wal.c | 2 +
src/backend/utils/adt/pgstatfuncs.c | 53 +++++++++++-
src/include/catalog/pg_proc.dat | 7 ++
src/include/pgstat.h | 48 +++++++----
src/include/utils/pgstat_internal.h | 3 +-
src/test/regress/expected/stats.out | 14 ++++
src/test/regress/sql/stats.sql | 6 ++
11 files changed, 253 insertions(+), 29 deletions(-)
12.5% doc/src/sgml/
11.2% src/backend/access/transam/
37.5% src/backend/utils/activity/
17.3% src/backend/utils/adt/
6.1% src/include/catalog/
6.3% src/include/
5.0% src/test/regress/expected/
3.8% src/test/regress/sql/
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index a8866292d46..5a48b427609 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -8292,7 +8292,9 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
measure the overhead of timing on your system.
I/O timing information is
displayed in <link linkend="monitoring-pg-stat-wal-view">
- <structname>pg_stat_wal</structname></link>.
+ <structname>pg_stat_wal</structname></link> and in the output of the
+ <link linkend="pg-stat-get-backend-wal">
+ <function>pg_stat_get_backend_wal()</function></link> function.
Only superusers and users with the appropriate <literal>SET</literal>
privilege can change this setting.
</para>
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index e5888fae2b5..8fdf7d13f21 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -4824,6 +4824,25 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para></entry>
</row>
+ <row>
+ <entry id="pg-stat-get-backend-wal" role="func_table_entry"><para role="func_signature">
+ <indexterm>
+ <primary>pg_stat_get_backend_wal</primary>
+ </indexterm>
+ <function>pg_stat_get_backend_wal</function> ( <type>integer</type> )
+ <returnvalue>record</returnvalue>
+ </para>
+ <para>
+ Returns WAL statistics about the backend with the specified
+ process ID. The output fields are exactly the same as the ones in the
+ <structname>pg_stat_wal</structname> view.
+ </para>
+ <para>
+ The function does not return WAL statistics for the checkpointer,
+ the background writer, the startup process and the autovacuum launcher.
+ </para></entry>
+ </row>
+
<row>
<entry role="func_table_entry"><para role="func_signature">
<indexterm>
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index bf3dbda901d..f7c5b1e5e3b 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -2058,6 +2058,11 @@ AdvanceXLInsertBuffer(XLogRecPtr upto, TimeLineID tli, bool opportunistic)
XLogWrite(WriteRqst, tli, false);
LWLockRelease(WALWriteLock);
PendingWalStats.wal_buffers_full++;
+
+ /* Add the per-backend related statistic */
+ if (pgstat_tracks_backend_bktype(MyBackendType))
+ PendingBackendStats.pending_wal.wal_buffers_full++;
+
TRACE_POSTGRESQL_WAL_BUFFER_WRITE_DIRTY_DONE();
}
/* Re-acquire WALBufMappingLock and retry */
@@ -2426,11 +2431,14 @@ XLogWrite(XLogwrtRqst WriteRqst, TimeLineID tli, bool flexible)
Size nleft;
ssize_t written;
instr_time start;
+ instr_time end;
/* OK to write the page(s) */
from = XLogCtl->pages + startidx * (Size) XLOG_BLCKSZ;
nbytes = npages * (Size) XLOG_BLCKSZ;
nleft = nbytes;
+ /* keep compiler quiet */
+ INSTR_TIME_SET_ZERO(end);
do
{
errno = 0;
@@ -2451,14 +2459,22 @@ XLogWrite(XLogwrtRqst WriteRqst, TimeLineID tli, bool flexible)
*/
if (track_wal_io_timing)
{
- instr_time end;
-
INSTR_TIME_SET_CURRENT(end);
INSTR_TIME_ACCUM_DIFF(PendingWalStats.wal_write_time, end, start);
}
PendingWalStats.wal_write++;
+ /* Add the per-backend related statistic */
+ if (pgstat_tracks_backend_bktype(MyBackendType))
+ {
+ PendingBackendStats.pending_wal.wal_write++;
+
+ if (track_wal_io_timing)
+ INSTR_TIME_ACCUM_DIFF(PendingBackendStats.pending_wal.wal_write_time,
+ end, start);
+ }
+
if (written <= 0)
{
char xlogfname[MAXFNAMELEN];
@@ -8684,8 +8700,11 @@ issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli)
{
char *msg = NULL;
instr_time start;
+ instr_time end;
Assert(tli != 0);
+ /* keep compiler quiet */
+ INSTR_TIME_SET_ZERO(end);
/*
* Quick exit if fsync is disabled or write() has already synced the WAL
@@ -8751,13 +8770,21 @@ issue_xlog_fsync(int fd, XLogSegNo segno, TimeLineID tli)
*/
if (track_wal_io_timing)
{
- instr_time end;
-
INSTR_TIME_SET_CURRENT(end);
INSTR_TIME_ACCUM_DIFF(PendingWalStats.wal_sync_time, end, start);
}
PendingWalStats.wal_sync++;
+
+ /* Add the per-backend related statistic */
+ if (pgstat_tracks_backend_bktype(MyBackendType))
+ {
+ PendingBackendStats.pending_wal.wal_sync++;
+
+ if (track_wal_io_timing)
+ INSTR_TIME_ACCUM_DIFF(PendingBackendStats.pending_wal.wal_sync_time,
+ end, start);
+ }
}
/*
diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index bcf9e4b1487..90fb5f72bc1 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -33,11 +33,18 @@
* reported within critical sections so we use static memory in order to avoid
* memory allocation.
*/
-static PgStat_BackendPending PendingBackendStats;
+PgStat_BackendPending PendingBackendStats;
/*
- * Utility routines to report I/O stats for backends, kept here to avoid
- * exposing PendingBackendStats to the outside world.
+ * WAL usage counters saved from pgWalUsage at the previous call to
+ * pgstat_report_wal(). This is used to calculate how much WAL usage
+ * happens between pgstat_report_wal() calls, by subtracting
+ * the previous counters from the current ones.
+ */
+static WalUsage prevBackendWalUsage;
+
+/*
+ * Utility routines to report I/O stats for backends.
*/
void
pgstat_count_backend_io_op_time(IOObject io_object, IOContext io_context,
@@ -131,6 +138,79 @@ pgstat_flush_backend_entry_io(PgStat_EntryRef *entry_ref)
MemSet(&PendingBackendStats.pending_io, 0, sizeof(PgStat_PendingIO));
}
+/*
+ * To determine whether any WAL activity has occurred since last time, not
+ * only the number of generated WAL records but also the numbers of WAL
+ * writes and syncs need to be checked. Because even transaction that
+ * generates no WAL records can write or sync WAL data when flushing the
+ * data pages.
+ */
+static bool
+pgstat_backend_wal_have_pending(void)
+{
+ PgStat_PendingWalStats pending_wal;
+
+ pending_wal = PendingBackendStats.pending_wal;
+
+ return pgWalUsage.wal_records != prevBackendWalUsage.wal_records ||
+ pending_wal.wal_write != 0 || pending_wal.wal_sync != 0;
+}
+
+/*
+ * Flush out locally pending backend WAL statistics. Locking is managed
+ * by the caller.
+ */
+static void
+pgstat_flush_backend_entry_wal(PgStat_EntryRef *entry_ref)
+{
+ PgStatShared_Backend *shbackendent;
+ PgStat_WalCounters *bktype_shstats;
+ PgStat_PendingWalStats pending_wal = PendingBackendStats.pending_wal;
+ WalUsage wal_usage_diff = {0};
+
+ /*
+ * This function can be called even if nothing at all has happened. Avoid
+ * taking lock for nothing in that case.
+ */
+ if (!pgstat_backend_wal_have_pending())
+ return;
+
+ shbackendent = (PgStatShared_Backend *) entry_ref->shared_stats;
+ bktype_shstats = &shbackendent->stats.wal_stats;
+
+ /*
+ * We don't update the WAL usage portion of the local WalStats elsewhere.
+ * Calculate how much WAL usage counters were increased by subtracting the
+ * previous counters from the current ones.
+ */
+ WalUsageAccumDiff(&wal_usage_diff, &pgWalUsage, &prevBackendWalUsage);
+
+#define WALSTAT_ACC(fld, var_to_add) \
+ (bktype_shstats->fld += var_to_add.fld)
+#define WALSTAT_ACC_INSTR_TIME(fld) \
+ (bktype_shstats->fld += INSTR_TIME_GET_MICROSEC(pending_wal.fld))
+ WALSTAT_ACC(wal_buffers_full, pending_wal);
+ WALSTAT_ACC(wal_write, pending_wal);
+ WALSTAT_ACC(wal_sync, pending_wal);
+ WALSTAT_ACC(wal_records, wal_usage_diff);
+ WALSTAT_ACC(wal_fpi, wal_usage_diff);
+ WALSTAT_ACC(wal_bytes, wal_usage_diff);
+ WALSTAT_ACC_INSTR_TIME(wal_write_time);
+ WALSTAT_ACC_INSTR_TIME(wal_sync_time);
+#undef WALSTAT_ACC_INSTR_TIME
+#undef WALSTAT_ACC
+
+ /*
+ * Save the current counters for the subsequent calculation of WAL usage.
+ */
+ prevBackendWalUsage = pgWalUsage;
+
+ /*
+ * Clear out the statistics buffer, so it can be re-used.
+ */
+ MemSet(&PendingBackendStats.pending_wal, 0, sizeof(PendingWalStats));
+}
+
/*
* Flush out locally pending backend statistics
*
@@ -158,6 +238,9 @@ pgstat_flush_backend(bool nowait, bits32 flags)
if (flags & PGSTAT_BACKEND_FLUSH_IO)
pgstat_flush_backend_entry_io(entry_ref);
+ if (flags & PGSTAT_BACKEND_FLUSH_WAL)
+ pgstat_flush_backend_entry_wal(entry_ref);
+
pgstat_unlock_entry(entry_ref);
return false;
@@ -205,6 +288,8 @@ pgstat_create_backend(ProcNumber procnum)
pgstat_unlock_entry(entry_ref);
MemSet(&PendingBackendStats, 0, sizeof(PgStat_BackendPending));
+
+ prevBackendWalUsage = pgWalUsage;
}
/*
diff --git a/src/backend/utils/activity/pgstat_wal.c b/src/backend/utils/activity/pgstat_wal.c
index bfc06178a68..33627642261 100644
--- a/src/backend/utils/activity/pgstat_wal.c
+++ b/src/backend/utils/activity/pgstat_wal.c
@@ -55,6 +55,8 @@ pgstat_report_wal(bool force)
/* flush wal stats */
pgstat_flush_wal(nowait);
+ pgstat_flush_backend(nowait, PGSTAT_BACKEND_FLUSH_WAL);
+
/* flush IO stats */
pgstat_flush_io(nowait);
}
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 97510d48eef..6da98bafbf2 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1606,8 +1606,8 @@ pg_stat_get_backend_io(PG_FUNCTION_ARGS)
/*
* pg_stat_wal_build_tuple
*
- * Helper routine for pg_stat_get_wal() returning one tuple based on the contents
- * of wal_counters.
+ * Helper routine for pg_stat_get_wal() and pg_stat_get_backend_wal() returning
+ * one tuple based on the contents of wal_counters.
*/
static Datum
pg_stat_wal_build_tuple(PgStat_WalCounters wal_counters,
@@ -1670,6 +1670,55 @@ pg_stat_wal_build_tuple(PgStat_WalCounters wal_counters,
PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
}
+/*
+ * Returns WAL statistics for a backend with given PID.
+ */
+Datum
+pg_stat_get_backend_wal(PG_FUNCTION_ARGS)
+{
+ int pid;
+ PGPROC *proc;
+ ProcNumber procNumber;
+ PgStat_Backend *backend_stats;
+ PgStat_WalCounters bktype_stats;
+ PgBackendStatus *beentry;
+
+ pid = PG_GETARG_INT32(0);
+ proc = BackendPidGetProc(pid);
+
+ /*
+ * This could be an auxiliary process but these do not report backend
+ * statistics due to pgstat_tracks_backend_bktype(), so there is no need
+ * for an extra call to AuxiliaryPidGetProc().
+ */
+ if (!proc)
+ PG_RETURN_NULL();
+
+ procNumber = GetNumberFromPGProc(proc);
+
+ beentry = pgstat_get_beentry_by_proc_number(procNumber);
+ if (!beentry)
+ PG_RETURN_NULL();
+
+ backend_stats = pgstat_fetch_stat_backend(procNumber);
+ if (!backend_stats)
+ PG_RETURN_NULL();
+
+ /* if PID does not match, leave */
+ if (beentry->st_procpid != pid)
+ PG_RETURN_NULL();
+
+ /* backend may be gone, so recheck in case */
+ if (beentry->st_backendType == B_INVALID)
+ PG_RETURN_NULL();
+
+ bktype_stats = backend_stats->wal_stats;
+
+ /* save tuples with data from this PgStat_BktypeIO */
+ return (pg_stat_wal_build_tuple(bktype_stats, backend_stats->stat_reset_timestamp));
+}
+
+
/*
* Returns statistics of WAL activity
*/
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 18560755d26..ca60af1e434 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -5929,6 +5929,13 @@
proargmodes => '{o,o,o,o,o,o,o,o,o}',
proargnames => '{wal_records,wal_fpi,wal_bytes,wal_buffers_full,wal_write,wal_sync,wal_write_time,wal_sync_time,stats_reset}',
prosrc => 'pg_stat_get_wal' },
+{ oid => '8037', descr => 'statistics: backend WAL activity',
+ proname => 'pg_stat_get_backend_wal', provolatile => 'v',
+ proparallel => 'r', prorettype => 'record', proargtypes => 'int4',
+ proallargtypes => '{int4,int8,int8,numeric,int8,int8,int8,float8,float8,timestamptz}',
+ proargmodes => '{i,o,o,o,o,o,o,o,o,o}',
+ proargnames => '{backend_pid,wal_records,wal_fpi,wal_bytes,wal_buffers_full,wal_write,wal_sync,wal_write_time,wal_sync_time,stats_reset}',
+ prosrc => 'pg_stat_get_backend_wal' },
{ oid => '6248', descr => 'statistics: information about WAL prefetching',
proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't',
provolatile => 'v', prorettype => 'record', proargtypes => '',
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 9bbba883685..27a0053ea21 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -338,24 +338,6 @@ typedef struct PgStat_IO
PgStat_BktypeIO stats[BACKEND_NUM_TYPES];
} PgStat_IO;
-typedef struct PgStat_Backend
-{
- TimestampTz stat_reset_timestamp;
- PgStat_BktypeIO io_stats;
-} PgStat_Backend;
-
-/* ---------
- * PgStat_BackendPending Non-flushed backend stats.
- * ---------
- */
-typedef struct PgStat_BackendPending
-{
- /*
- * Backend statistics store the same amount of IO data as PGSTAT_KIND_IO.
- */
- PgStat_PendingIO pending_io;
-} PgStat_BackendPending;
-
typedef struct PgStat_StatDBEntry
{
PgStat_Counter xact_commit;
@@ -500,6 +482,30 @@ typedef struct PgStat_PendingWalStats
instr_time wal_sync_time;
} PgStat_PendingWalStats;
+/* ---------
+ * PgStat_BackendPending Non-flushed backend stats.
+ * ---------
+ */
+typedef struct PgStat_BackendPending
+{
+ /*
+ * Backend statistics store the same amount of IO data as PGSTAT_KIND_IO.
+ */
+ PgStat_PendingIO pending_io;
+
+ /*
+ * Backend statistics store the same amount of WAL data as
+ * PGSTAT_KIND_WAL.
+ */
+ PgStat_PendingWalStats pending_wal;
+} PgStat_BackendPending;
+
+typedef struct PgStat_Backend
+{
+ TimestampTz stat_reset_timestamp;
+ PgStat_BktypeIO io_stats;
+ PgStat_WalCounters wal_stats;
+} PgStat_Backend;
/*
* Functions in pgstat.c
@@ -840,5 +846,11 @@ extern PGDLLIMPORT SessionEndType pgStatSessionEndCause;
/* updated directly by backends and background processes */
extern PGDLLIMPORT PgStat_PendingWalStats PendingWalStats;
+/*
+ * Variables in pgstat_backend.c
+ */
+
+/* updated directly by backends */
+extern PGDLLIMPORT PgStat_BackendPending PendingBackendStats;
#endif /* PGSTAT_H */
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index a3d39d2b725..6155a3fc983 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -622,7 +622,8 @@ extern void pgstat_archiver_snapshot_cb(void);
/* flags for pgstat_flush_backend() */
#define PGSTAT_BACKEND_FLUSH_IO (1 << 0) /* Flush I/O statistics */
-#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO)
+#define PGSTAT_BACKEND_FLUSH_WAL (1 << 1) /* Flush WAL statistics */
+#define PGSTAT_BACKEND_FLUSH_ALL (PGSTAT_BACKEND_FLUSH_IO | PGSTAT_BACKEND_FLUSH_WAL)
extern bool pgstat_flush_backend(bool nowait, bits32 flags);
extern bool pgstat_backend_flush_cb(bool nowait);
diff --git a/src/test/regress/expected/stats.out b/src/test/regress/expected/stats.out
index a0317b7208e..cc01fdf2741 100644
--- a/src/test/regress/expected/stats.out
+++ b/src/test/regress/expected/stats.out
@@ -832,6 +832,8 @@ SELECT sessions > :db_stat_sessions FROM pg_stat_database WHERE datname = (SELEC
SELECT num_requested AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
-- Test pg_stat_wal (and make a temp table so our temp schema exists)
SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
+-- Test pg_stat_get_backend_wal (and make a temp table so our temp schema exists)
+SELECT wal_bytes AS backend_wal_bytes_before from pg_stat_get_backend_wal(pg_backend_pid()) \gset
CREATE TEMP TABLE test_stats_temp AS SELECT 17;
DROP TABLE test_stats_temp;
-- Checkpoint twice: The checkpointer reports stats after reporting completion
@@ -851,6 +853,18 @@ SELECT wal_bytes > :wal_bytes_before FROM pg_stat_wal;
t
(1 row)
+SELECT pg_stat_force_next_flush();
+ pg_stat_force_next_flush
+--------------------------
+
+(1 row)
+
+SELECT wal_bytes > :backend_wal_bytes_before FROM pg_stat_get_backend_wal(pg_backend_pid());
+ ?column?
+----------
+ t
+(1 row)
+
-- Test pg_stat_get_backend_idset() and some allied functions.
-- In particular, verify that their notion of backend ID matches
-- our temp schema index.
diff --git a/src/test/regress/sql/stats.sql b/src/test/regress/sql/stats.sql
index 399c72bbcf7..28fe0a1a7d0 100644
--- a/src/test/regress/sql/stats.sql
+++ b/src/test/regress/sql/stats.sql
@@ -423,6 +423,9 @@ SELECT num_requested AS rqst_ckpts_before FROM pg_stat_checkpointer \gset
-- Test pg_stat_wal (and make a temp table so our temp schema exists)
SELECT wal_bytes AS wal_bytes_before FROM pg_stat_wal \gset
+-- Test pg_stat_get_backend_wal (and make a temp table so our temp schema exists)
+SELECT wal_bytes AS backend_wal_bytes_before from pg_stat_get_backend_wal(pg_backend_pid()) \gset
+
CREATE TEMP TABLE test_stats_temp AS SELECT 17;
DROP TABLE test_stats_temp;
@@ -435,6 +438,9 @@ CHECKPOINT;
SELECT num_requested > :rqst_ckpts_before FROM pg_stat_checkpointer;
SELECT wal_bytes > :wal_bytes_before FROM pg_stat_wal;
+SELECT pg_stat_force_next_flush();
+SELECT wal_bytes > :backend_wal_bytes_before FROM pg_stat_get_backend_wal(pg_backend_pid());
+
-- Test pg_stat_get_backend_idset() and some allied functions.
-- In particular, verify that their notion of backend ID matches
-- our temp schema index.
--
2.34.1
