Re: See Temp Table from Trigger

>
> Hi List!
> Is there a way a Trigger can see a Temporary Table or better - check
if a
> Temp Table exists?
> - Or can i define a "Session Variable" that will allow this?

Joachim,
Find below a previuos thread on temp-table-existence.
Hope this helps.
Regards, Christoph

From: Mike Papper <m(dot)papper(at)fantastic(dot)com>
Subject: [SQL] Finding if a temp table exists in the current connection
Date: Wed, 02 Apr 2003 00:09:33 -0800

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?

--
Mike Papper

From: Christoph Haller <ch(at)rodos(dot)fzk(dot)de>
Subject: Re: [SQL] Finding if a temp table exists in the current
connection
Date: Fri, 04 Apr 2003 13:16:16 +0200

>
> 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

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: [SQL] Finding if a temp table exists in the current
connection
Date: Fri, 04 Apr 2003 09:58:24 -0500

Christoph Haller <ch(at)rodos(dot)fzk(dot)de> writes:
> It looks like they are created in name spaces called "pg_temp_<N>,
> where N is simply a connection counter.

Right. If you are trying to find out which N applies to your session,
here is one way:

regression=# select current_schemas(true);
current_schemas
---------------------
{pg_catalog,public}
(1 row)

regression=# create temp table z(f1 int);
CREATE TABLE
regression=# select current_schemas(true);
current_schemas
-------------------------------
{pg_temp_2,pg_catalog,public}
(1 row)

regards, tom lane