Alvaro Herrera wrote:
Tom Lane wrote:
Oh! What is happening is that to_number(1) is being reduced to constant
NULL, whereupon it concludes that ad_tab_id=to_number(1) is constant
NULL, ergo the EXISTS can never succeed, ergo the entire WHERE is
constant false.
CREATE FUNCTION to_number(integer) RETURNS numeric
LANGUAGE plpgsql IMMUTABLE
AS $_$
BEGIN
RETURN to_number($1, 'S99999999999999D999999');
EXCEPTION
WHEN OTHERS THEN
RETURN NULL;
END;
$_$;
How can the executor "see through" a plpgsql function definition? Or do
you mean that this reduction is being done at execution time? (hmm ...
this is what a one-time filter is, now that I think about it?)
Note that the function is immutable, and the argument in the query is a
constant. The planner simply runs the function and replaces the function
call with the result.
--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com
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