Re: [patch] [doc] Further note required activity aspect of automatic checkpoint and archving

On 2020-10-12 23:54, David G. Johnston wrote:
> --- a/doc/src/sgml/backup.sgml
> +++ b/doc/src/sgml/backup.sgml
> @@ -722,6 +722,8 @@ test ! -f 
> /mnt/server/archivedir/00000001000000A900000065 && cp pg_wal/0
>       short <varname>archive_timeout</varname> — it will bloat 
> your archive
>       storage.  <varname>archive_timeout</varname> settings of a minute 
> or so are
>       usually reasonable.
> +    This is mitigated by the fact that empty WAL segments will not be 
> archived
> +    even if the archive_timeout period has elapsed.
>      </para>

This is hopefully not what happens.  What this would mean is that I'd 
then have a sequence of WAL files named, say,

1, 2, 3, 7, 8, ...

because a few in the middle were not archived because they were empty.

> --- a/doc/src/sgml/config.sgml
> +++ b/doc/src/sgml/config.sgml
> @@ -3131,6 +3131,8 @@ include_dir 'conf.d'
>         <listitem>
>          <para>
>           Maximum time between automatic WAL checkpoints.
> +        The automatic checkpoint will do nothing if no new WAL has been
> +        written since the last recorded checkpoint.
>           If this value is specified without units, it is taken as seconds.
>           The valid range is between 30 seconds and one day.
>           The default is five minutes (<literal>5min</literal>).

I think what happens is that the checkpoint is skipped, not that the 
checkpoint happens but does nothing.  That is the wording you cited in 
the other thread from 
<https://www.postgresql.org/docs/13/wal-configuration.html>.