From: | David Schmitt <david(at)dasz(dot)at> |
---|---|
To: | pgsql-bugs(at)postgresql(dot)org |
Subject: | Re: BUG #5549: Feature: plpgsql should allow DECLARE cursor FOR EXECUTE '...' |
Date: | 2010-07-12 08:10:41 |
Message-ID: | 4C3ACE01.7010005@dasz.at |
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Lists: | pgsql-bugs |
On 7/9/2010 4:53 PM, Tom Lane wrote:
> "David Schmitt"<david(at)dasz(dot)at> writes:
>> This is not implemented:
>
>> DECLARE
>> working_cursor NO SCROLL CURSOR FOR EXECUTE $$SELECT something $$ || tbl
>> || $$ ... $$;
>
> What's wrong with OPEN FOR EXECUTE?
>
> The proposed addition seems a bit weird anyway since it presumes
> nontrivial calculation to be done during variable initialization.
I've investigated further and found that the correct formulation is:
FOR rec IN EXECUTE $$SELECT something $$ || tbl || $$ ... $$ LOOP
END LOOP
If I understand the documentation correctly this does exactly what I
need: open and close a cursor automatically with the dynamic statement
and loop over its result set. Actually, this is even more consise and to
the point that what I had in mind first.
This syntax is documented in the lower half of "Looping Through Query
Results"[1]. It is not mentioned in "Looping Through a Cursor's
Result"[2] where I would have (naively) expected it.
My confusion seems to arise from the fact that FOR loops are described
first without mentioning cursors at all and then a "different" FOR is
introduced specifically for use with cursors.
Thanks for your time and work, David Schmitt
[2]http://www.postgresql.org/docs/8.4/interactive/plpgsql-cursors.html#PLPGSQL-CURSOR-FOR-LOOP
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