From: Christoph Haller <ch@rodos.fzk.de>
To: pgsql-sql@postgresql.org
Cc: m.papper@fantastic.com
Subject: Re: Finding if a temp table exists in the current connection
Date: Fri, 04 Apr 2003 13:16:16 +0200
Message-ID: <3E8D6980.5060308@rodos.fzk.de> (raw)
>
> Is there a way (i.e., access theinternal pg_ tables) to find out if a
> particular temp table already exists (in the current connection)?
>
> I have written some stored procedures that check if a table exists
and if a
> column exists in a table. This is used so I can perform upgrades of our
> system (if table doesnt exist, call create table... sql).
>
> I would like to do a similar thing for temp tables.
>
> I have noticed that if another connection creates a temp table, it will
> show up in the pg_* tables so that all ocnnections can see the table.
>
> Is there some standard SQL way to test?
>
I'm using 7.3.2 and it seems there is a way.
I've found out by starting a psql session using the -E option.
This shows you the SQL behind \dt which shows the current temp tables.
It looks like they are created in name spaces called "pg_temp_<N>,
where N is simply a connection counter.
SELECT n.nspname as "Schema",c.relname as "Name"
FROM pg_catalog.pg_class c LEFT JOIN pg_catalog.pg_namespace n ON n.oid
= c.relnamespace
where n.nspname like 'pg_temp_%' AND pg_catalog.pg_table_is_visible(c.oid) ;
If I do (within 1st connection)
create temp table tgif (dummy int);
and the select above returns
Schema | Name
-----------+------
pg_temp_1 | tgif
(1 row)
And within a 2nd connection
create temp table tgif (dummy int);
and the select above returns
Schema | Name
-----------+------
pg_temp_2 | tgif
(1 row)
Does this help?
Regards, Christoph
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To: pgsql-sql@postgresql.org
Cc: ch@rodos.fzk.de, m.papper@fantastic.com
Subject: Re: Finding if a temp table exists in the current connection
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