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doc: Improve pg_stat_recovery documentation

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Improve the documentation for pg_stat_recovery in several ways:

- Mention the view in high-availability.sgml as a way to monitor
  recovery state and replay progress, alongside the existing recovery
  information functions.
- Clarify that the view returns at most one row, not exactly one row,
  and no rows to users who lack the pg_read_all_stats privilege.
- Correct the description of last_replayed_end_lsn to clarify that it
  is the end LSN of the last replayed record plus one.
- Document that replay_end_tli equals last_replayed_tli when no WAL
  record is currently being replayed.
- Clarify that current_chunk_start_time is NULL until streaming WAL
  has been received.

Backpatch to v19, where pg_stat_recovery was introduced.

Author: Fujii Masao <masao.fujii@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/CAHGQGwGRavm18HqnQn_f68QB96qk6arhjET1V93OJH09Mgojkg@mail.gmail.com
Backpatch-through: 19
This commit is contained in:
Fujii Masao
2026-07-23 19:22:36 +09:00
parent 703859d7c6
commit 42b480d286
3 changed files with 30 additions and 20 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
doc/src/sgml/high-availability.sgml
View File

@@ -920,7 +920,10 @@ primary_conninfo = 'host=192.168.1.50 port=5432 user=foo password=foopass'
<structname>pg_stat_wal_receiver</structname></link> view. A large
difference between <function>pg_last_wal_replay_lsn</function> and the
view's <literal>flushed_lsn</literal> indicates that WAL is being
received faster than it can be replayed.
received faster than it can be replayed. Recovery state and replay
progress can also be monitored via the
<link linkend="monitoring-pg-stat-recovery-view">
<structname>pg_stat_recovery</structname></link> view.
</para>
</sect3>
</sect2>
@@ -1801,9 +1804,11 @@ postgres=# WAIT FOR LSN '0/306EE20';
(In server versions before 14, the <varname>in_hot_standby</varname>
parameter did not exist; a workable substitute method for older servers
is <command>SHOW transaction_read_only</command>.) In addition, a set of
functions (<xref linkend="functions-recovery-info-table"/>) allow users to
access information about the standby server. These allow you to write
programs that are aware of the current state of the database. These
functions (<xref linkend="functions-recovery-info-table"/>) and the
<link linkend="monitoring-pg-stat-recovery-view">
<structname>pg_stat_recovery</structname></link> view allow users to
access information about the standby server. These facilities allow you to
write programs that are aware of the current state of the database. They
can be used to monitor the progress of recovery, or to allow you to
write complex programs that restore the database to particular states.
</para>

33
doc/src/sgml/monitoring.sgml
View File

@@ -340,7 +340,7 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
<row>
<entry><structname>pg_stat_recovery</structname><indexterm><primary>pg_stat_recovery</primary></indexterm></entry>
<entry>Only one row, showing statistics about the state of recovery.
<entry>At most one row, showing statistics about the recovery state.
See <link linkend="monitoring-pg-stat-recovery-view">
<structname>pg_stat_recovery</structname></link> for details.
</entry>
@@ -1965,9 +1965,11 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</indexterm>
<para>
The <structname>pg_stat_recovery</structname> view will contain only
The <structname>pg_stat_recovery</structname> view will contain at most
one row, showing statistics about the recovery state of the startup
process. This view returns no row when the server is not in recovery.
process. This view returns no rows when the server is not in recovery
or the user does not have privileges of the
<literal>pg_read_all_stats</literal> role.
</para>
<table id="pg-stat-recovery-view" xreflabel="pg_stat_recovery">
@@ -2009,8 +2011,8 @@ description | Waiting for a newly initialized WAL file to reach durable storage
<structfield>last_replayed_end_lsn</structfield> <type>pg_lsn</type>
</para>
<para>
End write-ahead log location of the last successfully replayed
WAL record.
End write-ahead log location, plus one, of the last successfully
replayed WAL record.
</para></entry>
</row>
@@ -2039,18 +2041,20 @@ description | Waiting for a newly initialized WAL file to reach durable storage
<structfield>replay_end_tli</structfield> <type>integer</type>
</para>
<para>
Timeline of the WAL record currently being replayed.
Timeline of the WAL record currently being replayed. When no record
is being actively replayed, equals
<structfield>last_replayed_tli</structfield>.
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>recovery_last_xact_time</structfield> <type>timestamp with time zone</type>
</para>
<para>
Timestamp of the last transaction commit or abort replayed during
recovery. This is the time at which the commit or abort WAL record
for that transaction was generated on the primary.
<structfield>recovery_last_xact_time</structfield> <type>timestamp with time zone</type>
</para>
<para>
Timestamp of the last transaction commit or abort record replayed
during recovery. This is the time at which the commit or abort WAL
record for that transaction was generated on the primary.
</para></entry>
</row>
@@ -2060,8 +2064,9 @@ description | Waiting for a newly initialized WAL file to reach durable storage
</para>
<para>
Time when the startup process observed that replay had caught up
with the latest received WAL chunk. Used in recovery-conflict
timing and replay/apply-lag diagnostics. NULL if not yet
with the latest WAL chunk received from streaming replication.
Used in recovery-conflict timing and replay/apply-lag diagnostics.
NULL if streaming WAL has not yet been received or the time is not
available.
</para></entry>
</row>

4
src/include/access/xlogrecovery.h
View File

@@ -112,8 +112,8 @@ typedef struct XLogRecoveryCtlData
TimestampTz recoveryLastXTime;
/*
* timestamp of when we started replaying the current chunk of WAL data,
* only relevant for replication or archive recovery
* timestamp of when we caught up with the latest WAL chunk received from
* streaming replication
*/
TimestampTz currentChunkStartTime;
/* Recovery pause state */