At Wed, 21 Apr 2021 10:43:30 +0900 (JST), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in
> At Tue, 20 Apr 2021 13:32:35 +0900 (JST), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in
> > Hello.
> >
> > It seems to me that there's a stale description in the documentation
> > of pg_basebackup.
> >
> > https://www.postgresql.org/docs/13/app-pgbasebackup.html
> >
> > > Note that there are some limitations in taking a backup from a standby:
> > ...
> > > If you are using -X none, there is no guarantee that all WAL files
> > > required for the backup are archived at the end of backup.
> >
> > Actually, pg_basebackup waits for the all required files to be
> > archived, which is an established behavior by commit
> > 52f8a59dd9@PG10. However, the same commit seems to have forgot to
> > change the doc for pg_basebackup. (The current description is
> > introduced by 9a4d51077c@PG10)
> >
> > The attached is a proposal to rewrite it as the following.
> >
> > + If you are using -X none, pg_basebackup may wait for a long time for
> > + all the required WAL files to be archived. In that case, You may need
> > + to call pg_switch_wal() on the primary to complete it sooner.
>
> I forgot to preserve the description about *primary*. It should be as
> the following instead.
>
> + If you are using -X none, there is no guarantee on the primary that
> + all WAL files required for the backup are archived at the end of
> + backup. When the standby is configured as archive_mode=always,
> + pg_basebackup may wait for a long time for all the required WAL files
> + to be archived. In that case, You may need to call pg_switch_wal() on
> + the primary to complete it sooner.
Hmm. Some words need to be qualified. Attached.
regards.
--
Kyotaro Horiguchi
NTT Open Source Software Center
diff --git a/doc/src/sgml/ref/pg_basebackup.sgml b/doc/src/sgml/ref/pg_basebackup.sgml
index a3e292d44a..15e48f5a8e 100644
--- a/doc/src/sgml/ref/pg_basebackup.sgml
+++ b/doc/src/sgml/ref/pg_basebackup.sgml
@@ -83,8 +83,14 @@ PostgreSQL documentation
</listitem>
<listitem>
<para>
- If you are using <literal>-X none</literal>, there is no guarantee that all
- WAL files required for the backup are archived at the end of backup.
+ If you are using <literal>-X none</literal>, there is no guarantee on
+ the primary that all WAL files required for the backup are archived at
+ the end of backup. When <varname>archive_mode</varname> is set
+ to <literal>on</literal> on the
+ standby, <application>pg_basebackup</application> may wait for a long
+ time for all the required WAL files to be archived. In that case, You
+ may need to call <function>pg_switch_wal()</function> on the primary to
+ complete it sooner.
</para>
</listitem>
<listitem>
