Reliably finding temporary table

Help! I have a similar problem. Does anybody know how to solve a problem

2005/6/8, Ian Burrell <ianburrell@gmail.com>:

We have some functions which need to dynamically create a temporary
table if it does not already exist. We use the following function:

CREATE OR REPLACE FUNCTION test_date_time_exists() RETURNS BOOLEAN AS '
BEGIN
RETURN EXISTS (
SELECT * FROM pg_class
WHERE relname = ''test_date_time''
AND pg_table_is_visible(oid)
);
END;
' LANGUAGE 'plpgsql' STABLE

However, this has been failing occassionally with errors like

ERROR: cache lookup failed for relation 3454264547

From looking in the list archives, I found a description of
pg_table_is_visible failing because it has different snapshot
semantics than the SELECT. Is there a solution for this problem? Is
there another function I can use? What is a better way to detect temp
tables visible to the session?

- Ian

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On Tue, Jun 07, 2005 at 04:01:02PM -0700, Ian Burrell wrote:

CREATE OR REPLACE FUNCTION test_date_time_exists() RETURNS BOOLEAN AS '
BEGIN
RETURN EXISTS (
SELECT * FROM pg_class
WHERE relname = ''test_date_time''
AND pg_table_is_visible(oid)
);
END;
' LANGUAGE 'plpgsql' STABLE

However, this has been failing occassionally with errors like

ERROR: cache lookup failed for relation 3454264547

The following message suggests using CASE and has_schema_privilege()
along with pg_table_is_visible():

http://archives.postgresql.org/pgsql-hackers/2005-06/msg00319.php

If you're using PostgreSQL 8.0 then I'd expect an exception handler
to work:

CREATE FUNCTION create_test_date_time() RETURNS void AS $$
BEGIN
BEGIN
CREATE TEMPORARY TABLE test_date_time (...);
EXCEPTION
WHEN DUPLICATE_TABLE THEN
NULL;
END;

RETURN;
END;
$$ LANGUAGE plpgsql VOLATILE;

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/