Обсуждение: trigger run of archive_command?

Hi,

I want to do online backup saving the WAL files. So I set the database into
backup mode, make a backup, and then set the datbase to normal mode with
pg_stop_backup().
To make the backup complete, I need to backup the actual WAL file too, but
this one is still open when I run pg_stop_backup(), so I want to trigger the
archive_command to be sure that I don't miss anything.
In postgresql.conf I have defined an archive_command in postgresql.conf to
tell postgres what to do when the WAL file reaches a maximum filesize.

I use postgresql 8.1.4, so I only can make the archive_command depend on the
size of the WAL files, right now the maximum size of a WAL file is defined
to 16mb.
As a workaround I could create a dummy table, insert 16MB to make sure the
WAL files get rotated, and then I can backup the last WAL file.

But my hope is that there is an easier way, e.g. do I can use a trigger to
force the archive_command or any other mechanism?

kind regards
Sebastian

Hi,

> this one is still open when I run pg_stop_backup(), so I want to trigger the
> archive_command to be sure that I don't miss anything.

I guess what you want is pg_switch_xlog() (see
http://www.postgresql.org/docs/8.2/static/functions-admin.html)
which became available with PG 8.2 ...


Thomas

Hi,

Thomas Karcher <thkarcher@gmx.de> wrote:
> Hi,
>
> > this one is still open when I run pg_stop_backup(), so I want to trigger
the
> > archive_command to be sure that I don't miss anything.
>
> I guess what you want is pg_switch_xlog() (see
> http://www.postgresql.org/docs/8.2/static/functions-admin.html)
this is exactly what I am looking for
> which became available with PG 8.2 ...
unfortunately right now I am stuck to PG 8.1.4.
I hope I can manage to upgrade without too much hassle, it seems meanwhile I
have to use my workaround.

thanks a lot
Sebastian

Hello,

On Mon, 14 Jan 2008 17:39:34 +0100 Sebastian Reitenbach wrote:

> Thomas Karcher <thkarcher@gmx.de> wrote:
> >
> > > this one is still open when I run pg_stop_backup(), so I want to trigger
> > > the archive_command to be sure that I don't miss anything.
> >
> > I guess what you want is pg_switch_xlog() (see
> > http://www.postgresql.org/docs/8.2/static/functions-admin.html)
> this is exactly what I am looking for
> > which became available with PG 8.2 ...
> unfortunately right now I am stuck to PG 8.1.4.
> I hope I can manage to upgrade without too much hassle, it seems meanwhile I
> have to use my workaround.

a very rude hack is to produce enough changes so that PG will rotate
the logfile anyway:

CHECKPOINT;
CREATE TABLE xlog_switch AS SELECT
'0123456789ABCDE'::VARCHAR FROM generate_series(1,300000);
DROP TABLE xlog_switch;

This is a lot of overhead, but it does the job.


Kind regards

--
                Andreas 'ads' Scherbaum
German PostgreSQL User Group

Hi,
Andreas 'ads' Scherbaum <adsmail@wars-nicht.de> wrote:
>
> Hello,
>
> On Mon, 14 Jan 2008 17:39:34 +0100 Sebastian Reitenbach wrote:
>
> > Thomas Karcher <thkarcher@gmx.de> wrote:
> > >
> > > > this one is still open when I run pg_stop_backup(), so I want to
trigger
> > > > the archive_command to be sure that I don't miss anything.
> > >
> > > I guess what you want is pg_switch_xlog() (see
> > > http://www.postgresql.org/docs/8.2/static/functions-admin.html)
> > this is exactly what I am looking for
> > > which became available with PG 8.2 ...
> > unfortunately right now I am stuck to PG 8.1.4.
> > I hope I can manage to upgrade without too much hassle, it seems
meanwhile I
> > have to use my workaround.
>
> a very rude hack is to produce enough changes so that PG will rotate
> the logfile anyway:
>
> CHECKPOINT;
> CREATE TABLE xlog_switch AS SELECT
> '0123456789ABCDE'::VARCHAR FROM generate_series(1,300000);
> DROP TABLE xlog_switch;
>
> This is a lot of overhead, but it does the job.
until we upgrade, we do it in a very similar way.

thanks
Sebastian