Re: How to access multicolumn function results?

Andreas <maps(dot)on(at)gmx(dot)net> writes:
> SELECT some_fct( some_id ) FROM some_other_table;
> How can I split this up to look like a normal table or view with the
> column names that are defined in the RETURNS TABLE ( ... ) expression of
> the function.

The easy way is

SELECT (some_fct(some_id)).* FROM some_other_table;

If you're not too concerned about efficiency, you're done. However this
isn't very efficient, because the way the parser deals with expanding
the "*" is to make N copies of the function call, as you can see with
EXPLAIN VERBOSE --- you'll see something similar to

Output: (some_fct(some_id)).fld1, (some_fct(some_id)).fld2, ...

If the function is expensive enough that that's a problem, the basic
way to fix it is

SELECT (ss.x).* FROM
(SELECT some_fct(some_id) AS x FROM some_other_table) ss;

With a RETURNS TABLE function, this should be good enough. With simpler
functions you might have to insert OFFSET 0 into the sub-select to keep
the planner from "flattening" it into the upper query and producing the
same multiple-evaluation situation.

regards, tom lane