| From: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> |
| Cc: | 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 16:17:20 |
| Message-ID: | 41ebf7c5-ff95-4f37-833e-bea9b25963c1@2ndquadrant.com |
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| Lists: | pgsql-hackers |
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.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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