"CREATE TEMPORARY TABLE" does not work in SQL language function?

[David Johnston]

The only difference between the following two "CREATE FUNCTION" command is
the language in which they are written.



I do not recall and cannot seem to find after a quick search any limitation
regarding the use of "CREATE TEMPORARY TABLE" in an SQL language function.
It is not one of "BEGIN, COMMIT, ROLLBACK, SAVEPOINT" which are the only
explicit ones listed. DDL commands are neither explicitly prohibited nor
allowed but the phase "as well as other SQL commands" is too vague to be
authoritative.



version

PostgreSQL 9.0.4, compiled by Visual C++ build 1500, 64-bit



--SQL Language Function Fails

--SQL Error: ERROR: relation "temptbl" does not exist

--LINE 10: SELECT (one || two)::varchar AS result FROM temptbl;



SET LOCAL search_path = public;

CREATE FUNCTION temptabletest()

RETURNS varchar

AS $$



CREATE TEMPORARY TABLE temptbl

ON COMMIT DROP

AS SELECT '1'::varchar AS one, 'A'::varchar AS two;



SELECT (one || two)::varchar AS result FROM temptbl;

$$

LANGUAGE sql

STRICT

VOLATILE

;



While the following pl/pgsql function works:



SET LOCAL search_path = public;

CREATE FUNCTION temptabletest()

RETURNS varchar

AS $$

BEGIN

CREATE TEMPORARY TABLE temptbl

ON COMMIT DROP

AS SELECT '1'::varchar AS one, 'A'::varchar AS two;



RETURN (SELECT (one || two)::varchar AS result FROM temptbl);

END;

$$

LANGUAGE plpgsql

STRICT

VOLATILE

;



Thanks!



David J.

[Tom Lane]

Post by David Johnston
The only difference between the following two "CREATE FUNCTION" command is
the language in which they are written.

The reason the SQL function doesn't work is that SQL functions parse and
analyze their whole bodies before beginning execution --- so "temptbl"
doesn't exist yet when the SELECT is analyzed. It's not about temp
tables as such, but rather that any DDL that affects the meaning of
later statements is problematic.

IIRC, there have been a few discussions about changing this behavior,
but nothing's been done, partly out of fear of breaking existing
applications.

regards, tom lane