From: | Magnus Hagander <magnus(at)hagander(dot)net> |
---|---|
To: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>, Konstantin Knizhnik <k(dot)knizhnik(at)postgrespro(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: AS OF queries |
Date: | 2017-12-20 16:26:29 |
Message-ID: | CABUevEwoy2RLuZfmDs7DgTJ6C4bTUevozqHVQCquCOXDhcVY4g@mail.gmail.com |
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Lists: | pgsql-hackers |
On Wed, Dec 20, 2017 at 5:17 PM, Peter Eisentraut <
peter(dot)eisentraut(at)2ndquadrant(dot)com> wrote:
> On 12/20/17 10:29, Tom Lane wrote:
> > Please say that's just an Oracle-ism and not SQL standard, because it's
> > formally ambiguous. This is required to work by spec:
> >
> > regression=# select x as of from (values(1)) t(x);
> > of
> > ----
> > 1
> > (1 row)
> >
> > so it's not possible for us ever to support an expression that includes
> > top-level "AS OF" (or, pretty much, "AS anything") without some rather
> > enormous pushups.
>
> The SQL standard syntax appears to be something like
>
> "tablename" [ AS OF SYSTEM TIME 'something' ] [ [ AS ] "alias" ]
>
> That's not going to be fun to parse.
>
There was a presentation about this given at FOSDEM PGDay a couple of years
back. Slides at
https://wiki.postgresql.org/images/6/64/Fosdem20150130PostgresqlTemporal.pdf
.
--
Magnus Hagander
Me: https://www.hagander.net/ <http://www.hagander.net/>
Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>
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