Re: enabling join_collapse_limit for a single query only - Mailing list pgsql-general

From Matt Harrison
Subject Re: enabling join_collapse_limit for a single query only
Date
Msg-id DAD3D789-16B6-48F5-92D9-374F3B0F94E1@gmail.com
Whole thread Raw
In response to Re: enabling join_collapse_limit for a single query only  ("Albe Laurenz" <laurenz.albe@wien.gv.at>)
List pgsql-general
Hi, and thanks for the reply.

We're issuing queries from within our application where transactions
span a whole unit of work, so wrapping a single query in a transaction
just to set the param isn't really feasible except on a separate
connection, which i am loathe to do.

I was really hoping to be able to set join_collapse_limit=1 *just* on
the single query, as a kind of query hint, eg:

/* !hint:join_collapse_limit=1  */ SELECT ...

I take it this is this not possible in postgres?

cheers,
Matt h

On 23/07/2009, at 09:50, Albe Laurenz wrote:

> groovefillet wrote:
>> Is it possible to set the runtime parameter 'join_collapse_limit' for
>> a single query only without setting/unsetting it before/after?
>
> Yes:
>
> START TRANSACTION;
>
> SET LOCAL join_collapse_limit = 42;
>
> SELECT .....
>
> COMMIT;
>
> Yours,
> Laurenz Albe


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