Re: [HACKERS] make async slave to wait for lsn to be replayed

On Wed, Apr 8, 2020 at 2:14 AM Kartyshov Ivan
<i(dot)kartyshov(at)postgrespro(dot)ru> wrote:
> On 2020-04-08 00:27, Tom Lane wrote:
> > Alexander Korotkov <akorotkov(at)postgresql(dot)org> writes:
> » 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?
> > Plus, each new keyword carries the risk of breaking existing
> > applications, since it no longer works as an alias-not-preceded-by-AS.
> >
>
> To avoid creating new keywords, we could change syntax in the following
> way:
> WAIT FOR => DEPENDS ON

Looks OK for me.

> LSN => EVENT

I think it's too generic. Not every event is lsn. TBH, lsn is not
event at all :)

I wonder is we can still use word lsn, but don't use keyword for that.
Can we take arbitrary non-quoted literal there and check it later?

> TIMEOUT => WITH INTERVAL

I'm not yet sure about this. Probably there are better options.

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