From ff10d7684ead9efd0b7f6ff03b68d598917c7c5c Mon Sep 17 00:00:00 2001 From: Shinya Kato Date: Sat, 18 Oct 2025 16:27:32 +0900 Subject: [PATCH v2 1/2] Add wal_fpi_bytes to pg_stat_wal Track the total size of full-page images in WAL statistics so that the effect of wal_compression can be monitored. XLogRecordAssemble now increments a new wal_fpi_bytes counter in WalUsage, and the backend and shared WAL stats paths flush that value alongside the existing counters. Expose the counter through pg_stat_get_wal(), pg_stat_get_backend_wal(), pg_stat_wal. Author: Shinya Kato Reviewed-by: Michael Paquier Discusssion: https://postgr.es/m/CAOzEurQtZEAfg6P0kU3Wa-f9BWQOi0RzJEMPN56wNTOmJLmfaQ@mail.gmail.com --- doc/src/sgml/monitoring.sgml | 11 +++++++++++ src/backend/access/transam/xloginsert.c | 6 ++++++ src/backend/catalog/system_views.sql | 3 ++- src/backend/utils/activity/pgstat_backend.c | 1 + src/backend/utils/activity/pgstat_wal.c | 1 + src/backend/utils/adt/pgstatfuncs.c | 10 +++++++++- src/include/catalog/pg_proc.dat | 12 ++++++------ src/include/executor/instrument.h | 1 + src/include/pgstat.h | 1 + src/test/regress/expected/rules.out | 5 +++-- 10 files changed, 41 insertions(+), 10 deletions(-) diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml index d5f0fb7ba7c..0db378ee99e 100644 --- a/doc/src/sgml/monitoring.sgml +++ b/doc/src/sgml/monitoring.sgml @@ -3340,6 +3340,17 @@ description | Waiting for a newly initialized WAL file to reach durable storage Time at which these statistics were last reset + + + + wal_fpi_bytes numeric + + + Total amount of WAL full page images in bytes; if + wal_compression is enabled, this reflects the + compressed size + + diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c index 496e0fa4ac6..b3abf386f80 100644 --- a/src/backend/access/transam/xloginsert.c +++ b/src/backend/access/transam/xloginsert.c @@ -33,12 +33,14 @@ #include "access/xloginsert.h" #include "catalog/pg_control.h" #include "common/pg_lzcompress.h" +#include "executor/instrument.h" #include "miscadmin.h" #include "pg_trace.h" #include "replication/origin.h" #include "storage/bufmgr.h" #include "storage/proc.h" #include "utils/memutils.h" +#include "utils/pgstat_internal.h" /* * Guess the maximum buffer size required to store a compressed version of @@ -796,6 +798,10 @@ XLogRecordAssemble(RmgrId rmid, uint8 info, } total_len += bimg.length; + + /* Track the WAL full page images in bytes */ + pgWalUsage.wal_fpi_bytes += bimg.length; + pgstat_report_fixed = true; } if (needs_data) diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql index 823776c1498..d7f149f9328 100644 --- a/src/backend/catalog/system_views.sql +++ b/src/backend/catalog/system_views.sql @@ -1222,7 +1222,8 @@ CREATE VIEW pg_stat_wal AS w.wal_fpi, w.wal_bytes, w.wal_buffers_full, - w.stats_reset + w.stats_reset, + w.wal_fpi_bytes FROM pg_stat_get_wal() w; CREATE VIEW pg_stat_progress_analyze AS diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c index a864ae8e6a6..199ba2cc17a 100644 --- a/src/backend/utils/activity/pgstat_backend.c +++ b/src/backend/utils/activity/pgstat_backend.c @@ -252,6 +252,7 @@ pgstat_flush_backend_entry_wal(PgStat_EntryRef *entry_ref) WALSTAT_ACC(wal_records, wal_usage_diff); WALSTAT_ACC(wal_fpi, wal_usage_diff); WALSTAT_ACC(wal_bytes, wal_usage_diff); + WALSTAT_ACC(wal_fpi_bytes, wal_usage_diff); #undef WALSTAT_ACC /* diff --git a/src/backend/utils/activity/pgstat_wal.c b/src/backend/utils/activity/pgstat_wal.c index 0d04480d2f6..4d796c5e790 100644 --- a/src/backend/utils/activity/pgstat_wal.c +++ b/src/backend/utils/activity/pgstat_wal.c @@ -122,6 +122,7 @@ pgstat_wal_flush_cb(bool nowait) WALSTAT_ACC(wal_fpi, wal_usage_diff); WALSTAT_ACC(wal_bytes, wal_usage_diff); WALSTAT_ACC(wal_buffers_full, wal_usage_diff); + WALSTAT_ACC(wal_fpi_bytes, wal_usage_diff); #undef WALSTAT_ACC LWLockRelease(&stats_shmem->lock); diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c index 1fe33df2756..21efc010334 100644 --- a/src/backend/utils/adt/pgstatfuncs.c +++ b/src/backend/utils/adt/pgstatfuncs.c @@ -1637,7 +1637,7 @@ static Datum pg_stat_wal_build_tuple(PgStat_WalCounters wal_counters, TimestampTz stat_reset_timestamp) { -#define PG_STAT_WAL_COLS 5 +#define PG_STAT_WAL_COLS 6 TupleDesc tupdesc; Datum values[PG_STAT_WAL_COLS] = {0}; bool nulls[PG_STAT_WAL_COLS] = {0}; @@ -1655,6 +1655,8 @@ pg_stat_wal_build_tuple(PgStat_WalCounters wal_counters, INT8OID, -1, 0); TupleDescInitEntry(tupdesc, (AttrNumber) 5, "stats_reset", TIMESTAMPTZOID, -1, 0); + TupleDescInitEntry(tupdesc, (AttrNumber) 6, "wal_fpi_bytes", + NUMERICOID, -1, 0); BlessTupleDesc(tupdesc); @@ -1676,6 +1678,12 @@ pg_stat_wal_build_tuple(PgStat_WalCounters wal_counters, else nulls[4] = true; + snprintf(buf, sizeof buf, UINT64_FORMAT, wal_counters.wal_fpi_bytes); + values[5] = DirectFunctionCall3(numeric_in, + CStringGetDatum(buf), + ObjectIdGetDatum(0), + Int32GetDatum(-1)); + /* Returns the record as Datum */ PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls))); } diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat index eecb43ec6f0..952a51969b3 100644 --- a/src/include/catalog/pg_proc.dat +++ b/src/include/catalog/pg_proc.dat @@ -6029,16 +6029,16 @@ { oid => '1136', descr => 'statistics: information about WAL activity', proname => 'pg_stat_get_wal', proisstrict => 'f', provolatile => 's', proparallel => 'r', prorettype => 'record', proargtypes => '', - proallargtypes => '{int8,int8,numeric,int8,timestamptz}', - proargmodes => '{o,o,o,o,o}', - proargnames => '{wal_records,wal_fpi,wal_bytes,wal_buffers_full,stats_reset}', + proallargtypes => '{int8,int8,numeric,int8,timestamptz,numeric}', + proargmodes => '{o,o,o,o,o,o}', + proargnames => '{wal_records,wal_fpi,wal_bytes,wal_buffers_full,stats_reset,wal_fpi_bytes}', prosrc => 'pg_stat_get_wal' }, { oid => '6313', 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,timestamptz}', - proargmodes => '{i,o,o,o,o,o}', - proargnames => '{backend_pid,wal_records,wal_fpi,wal_bytes,wal_buffers_full,stats_reset}', + proallargtypes => '{int4,int8,int8,numeric,int8,timestamptz,numeric}', + proargmodes => '{i,o,o,o,o,o,o}', + proargnames => '{backend_pid,wal_records,wal_fpi,wal_bytes,wal_buffers_full,stats_reset,wal_fpi_bytes}', prosrc => 'pg_stat_get_backend_wal' }, { oid => '6248', descr => 'statistics: information about WAL prefetching', proname => 'pg_stat_get_recovery_prefetch', prorows => '1', proretset => 't', diff --git a/src/include/executor/instrument.h b/src/include/executor/instrument.h index 03653ab6c6c..7eb02833fad 100644 --- a/src/include/executor/instrument.h +++ b/src/include/executor/instrument.h @@ -54,6 +54,7 @@ typedef struct WalUsage int64 wal_fpi; /* # of WAL full page images produced */ uint64 wal_bytes; /* size of WAL records produced */ int64 wal_buffers_full; /* # of times the WAL buffers became full */ + uint64 wal_fpi_bytes; /* size of FPIs after compression */ } WalUsage; /* Flag bits included in InstrAlloc's instrument_options bitmask */ diff --git a/src/include/pgstat.h b/src/include/pgstat.h index bc8077cbae6..9c2d44bab89 100644 --- a/src/include/pgstat.h +++ b/src/include/pgstat.h @@ -473,6 +473,7 @@ typedef struct PgStat_WalCounters PgStat_Counter wal_records; PgStat_Counter wal_fpi; uint64 wal_bytes; + uint64 wal_fpi_bytes; PgStat_Counter wal_buffers_full; } PgStat_WalCounters; diff --git a/src/test/regress/expected/rules.out b/src/test/regress/expected/rules.out index 16753b2e4c0..6c3d78e96aa 100644 --- a/src/test/regress/expected/rules.out +++ b/src/test/regress/expected/rules.out @@ -2307,8 +2307,9 @@ pg_stat_wal| SELECT wal_records, wal_fpi, wal_bytes, wal_buffers_full, - stats_reset - FROM pg_stat_get_wal() w(wal_records, wal_fpi, wal_bytes, wal_buffers_full, stats_reset); + stats_reset, + wal_fpi_bytes + FROM pg_stat_get_wal() w(wal_records, wal_fpi, wal_bytes, wal_buffers_full, stats_reset, wal_fpi_bytes); pg_stat_wal_receiver| SELECT pid, status, receive_start_lsn, -- 2.47.3