Re: pgsql: Implement waiting for given lsn at transaction start

On Wed, Apr 8, 2020 at 12:27 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Alexander Korotkov <akorotkov@postgresql.org> writes:
> > Implement waiting for given lsn at transaction start
> > This commit adds following optional clause to BEGIN and START TRANSACTION
> > commands.
> >   WAIT FOR LSN lsn [ TIMEOUT timeout ]
>
> This seems like a really carelessly chosen syntax --- *three* new
> keywords, when you probably didn't need any.  Are you not aware that
> there is distributed overhead in the grammar for every keyword?

I had theoretical knowledge about that, but I didn't manage to apply it.

> Plus, each new keyword carries the risk of breaking existing
> applications, since it no longer works as an alias-not-preceded-by-AS.

I wasn't aware about this.  This is a good point, which I will remember.

> I have no particular opinion on the value of the feature, but I wish
> a different syntax had been chosen.

Sure, we'll prepare an update for syntax soon.

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company