Re: AS OF queries
| От | Magnus Hagander |
|---|---|
| Тема | Re: AS OF queries |
| Дата | |
| Msg-id | CABUevEwoy2RLuZfmDs7DgTJ6C4bTUevozqHVQCquCOXDhcVY4g@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: AS OF queries (Peter Eisentraut <peter.eisentraut@2ndquadrant.com>) |
| Список | pgsql-hackers |
On Wed, Dec 20, 2017 at 5:17 PM, Peter Eisentraut <peter.eisentraut@2ndquadrant.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.
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