2010/9/30 Pavel Stehule <pavel.stehule@gmail.com>:
> Hello
>
> 2010/9/30 Tom Lane <tgl@sss.pgh.pa.us>:
>> Vincenzo Romano <vincenzo.romano@notorand.it> writes:
>>> create or replace function session_init()
>>> returns void
>>> language plpgsql
>>> as $body$
>>> declare
>>> t text;
>>> begin
>>> select valu into t from session where name='SESSION_ID';
>>> if not found then
>>> create temporary table session ( like public.session including all );
>>> insert into session values ( 'SESSION_ID',current_user );
>>> end if;
>>> end;
>>> $body$;
>>
>>> The idea is to create a temporary table to store session variables
>>> only of there's no temporary table with that name.
>>
>> That isn't going to work tremendously well. plpgsql will cache a plan
>> for that SELECT on first use, and creation of the temp table is not an
>> event that will cause replanning of a select that doesn't already use
>> the temp table.
>>
>
> I found a little bit faster solution a catching a exception.
>
> http://okbob.blogspot.com/2008/11/plpgsql-and-temp-tables.html
Hmmm ... do you think the performance would be the same in v9?
> but if you need a session variables, then you can use a plperl
>
> http://www.postgresql.org/docs/9.0/static/plperl-global.html
I will look into this. What I need is a set of variable for each connection.
> Regards
>
> Pavel Stehule
Anyway, I'm quite puzzled by the fact that an EXCEPTION WHEN can be
faster than an IF .. THEN .. ELSE
with a rather simple test. Unless the pg_table_is_visible() is really bad.
Thanks a lot.
--
Vincenzo Romano at NotOrAnd Information Technologies
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