Check the existance of temporary table

Domenico-

Assuming your schema will be pg_temp_1
vi InitialTableDisplayStatements.sql
select * from pg_tables where pg_namespace = 'pg_temp1';

/usr/local/pgsql/bin/psql -f InitialTableDisplayStatements.sql -U username -h dbname -p Port > db.out

then write a quick java app to parse the db.out contents for 'Temp'

Ciao-
M--
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----- Original Message -----
From: "dfx" <dfx@dfx.it>
To: <pgsql-general@postgresql.org>
Sent: Sunday, March 25, 2007 8:32 AM
Subject: [GENERAL] Check the existance of temporary table

In article <BAY133-DAV980F324FFC1159F12BBF7AE680@phx.gbl>,
Martin Gainty <mgainty@hotmail.com> wrote:

% Assuming your schema will be pg_temp_1

Not a particularly reasonable assumption...

% vi InitialTableDisplayStatements.sql
% select * from pg_tables where pg_namespace = 'pg_temp1';

pmcphee=# select * from pg_tables where schemaname like 'pg_temp%';
schemaname | tablename | tableowner | tablespace | hasindexes | hasrules | hastriggers
------------+-----------+------------+------------+------------+----------+-------------
pg_temp_2 | x | pmcphee | x | f | f | f
(1 row)

pmcphee=# select * from x;
ERROR: relation "x" does not exist

But the test itself is problematic. I think this query is better.

select pg_table_is_visible(pg_class.oid)
from pg_class, pg_namespace
where relname = 'x' and
relnamespace = pg_namespace.oid and
nspname like 'pg_temp%';

From the same session where the select failed:

pmcphee=# select pg_table_is_visible(pg_class.oid)
pmcphee-# from pg_class, pg_namespace
pmcphee-# where relname = 'x' and
pmcphee-# relnamespace = pg_namespace.oid and
pmcphee-# nspname like 'pg_temp%';
pg_table_is_visible
---------------------
f
(1 row)

If I go on to create the temp table in the current session, this returns
pg_table_is_visible
---------------------
f
t
(2 rows)

so you need to be ready for more than one row, or sort the output and
put a limit on it.
--

Patrick TJ McPhee
North York Canada
ptjm@interlog.com

"dfx" <dfx@dfx.it> writes:

how I can check the existance of temporary table?
I.e. wich query I have to use to know if MY_TEMP_TABLE exists?

As of 8.2 you can do

SELECT ... FROM pg_class
WHERE relname = 'whatever' AND relnamespace = pg_my_temp_schema();

In earlier releases pg_my_temp_schema() isn't built in, so you have
to do some pushups to determine which schema is your temp schema.

regards, tom lane

In stored procedures I used something like

BEGIN
CREATE TEMPORARY TABLE tmp ...
EXCEPTION
WHEN ... THEN ...
END

See pg error codes for details (I don't remember exactly, but maybe it is a
dumplicate_table or duplicate_object exception).