Re: pgsql: Make DROP DATABASE command generate less WAL records.

On Thu, Nov 21, 2019 at 9:17 PM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
>
> On Thu, Nov 21, 2019 at 12:11:58PM +0000, Fujii Masao wrote:
> > Make DROP DATABASE command generate less WAL records.
> >
> > Previously DROP DATABASE generated as many XLOG_DBASE_DROP WAL records
> > as the number of tablespaces that the database to drop uses. This caused
> > the scans of shared_buffers as many times as the number of the tablespaces
> > during recovery because WAL replay of one XLOG_DBASE_DROP record needs
> > that full scan. This could make the recovery time longer especially
> > when shared_buffers is large.
> >
> > This commit changes DROP DATABASE so that it generates only one
> > XLOG_DBASE_DROP record, and registers the information of all the tablespaces
> > into it. Then, WAL replay of XLOG_DBASE_DROP record needs full scan of
> > shared_buffers only once, and which may improve the recovery performance.
>
> Fujii-san, you have forgotten to bump XLOG_PAGE_MAGIC in
> xlog_internal.h?

Thanks for pointing out that! Since the format of XLOG_DBASE_DROP WAL
record was changed, XLOG_PAGE_MAGIC must be bumped. Will do that.

Regards,

--
Fujii Masao