Search Postgresql Archives

Re: target list evaluation wrt sequences

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



>   elein <elein@varlena.com> wrote:
>> Is the order of the target list guaranteed?

AFAIR, all current and past Postgres versions evaluate target lists
left-to-right.  This is not guaranteed to remain true forever,
since neither the SQL spec nor our own docs promise it anywhere...
but offhand I can't think of a reason to break it.

Bruno Wolff III <bruno@wolff.to> writes:
> No. You can do effectively this by joining a select nextval to whatever
> you main select is. Something like:
> insert into ...
>        select a.n as a, a.n as b, ....
>              from (select nextval('n') as n) as a, lalala

Urgh ... I'd not want to promise that nextval() will always be evaluated
just once in the above example ... this really seems *much* more fragile
than assuming left-to-right targetlist evaluation :-(

			regards, tom lane

---------------------------(end of broadcast)---------------------------
TIP 5: Have you checked our extensive FAQ?

               http://www.postgresql.org/docs/faqs/FAQ.html

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Postgresql Jobs]     [Postgresql Admin]     [Postgresql Performance]     [Linux Clusters]     [PHP Home]     [PHP on Windows]     [Kernel Newbies]     [PHP Classes]     [PHP Books]     [PHP Databases]     [Postgresql & PHP]     [Yosemite]
  Powered by Linux