Обсуждение: wal_level and continuous archiving documentation

I was reading through
http://www.postgresql.org/docs/9.0/static/continuous-archiving.html and
noticed that wal_level isn't mentioned where I'd expect it to be.
Specifically, there's a paragraph that starts, "To enable WAL archiving, set
the archive_mode configuration parameter to on, and specify the shell command
to use in the archive_command configuration parameter." There follows a long
discussion of archive_command, but no further discussion of other
configuration settings for several paragraphs, suggesting that those two
configuration changes are the only ones required to end up with a useful
archive. However, further on, it discusses wal_level:
   "When wal_level is minimal some SQL commands are optimized to avoid WAL   logging, as described in Section 14.4.7.
Ifarchiving or streaming   replication were turned on during execution of one of these statements,   WAL would not
containenough information for archive recovery."
 

ISTM wal_archive should make an appearance where the docs bring up
archive_mode and archive_command, to say "wal_level must be set to 'archive'
or 'hot_standby'", so all required configuration changes are mentioned close
together.

--
Joshua Tolley / eggyknap
End Point Corporation
http://www.endpoint.com

On Fri, May 14, 2010 at 1:42 AM, Joshua Tolley <eggyknap@gmail.com> wrote:
> I was reading through
> http://www.postgresql.org/docs/9.0/static/continuous-archiving.html and
> noticed that wal_level isn't mentioned where I'd expect it to be.
> Specifically, there's a paragraph that starts, "To enable WAL archiving, set
> the archive_mode configuration parameter to on, and specify the shell command
> to use in the archive_command configuration parameter." There follows a long
> discussion of archive_command, but no further discussion of other
> configuration settings for several paragraphs, suggesting that those two
> configuration changes are the only ones required to end up with a useful
> archive. However, further on, it discusses wal_level:
>
>    "When wal_level is minimal some SQL commands are optimized to avoid WAL
>    logging, as described in Section 14.4.7. If archiving or streaming
>    replication were turned on during execution of one of these statements,
>    WAL would not contain enough information for archive recovery."
>
> ISTM wal_archive should make an appearance where the docs bring up
> archive_mode and archive_command, to say "wal_level must be set to 'archive'
> or 'hot_standby'", so all required configuration changes are mentioned close
> together.

Some descriptions about wal_level were added after beta1 release.
http://archives.postgresql.org/pgsql-committers/2010-05/msg00019.php

You can read the latest (development) document from
http://developer.postgresql.org/pgdocs/postgres/continuous-archiving.html

Regards,

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center