On tis, 2010-05-25 at 12:05 -0400, Richard Wallace wrote:
> 1) When using cursor_to_xml in a plpgsql function, the FOUND variable does 
> not seem to get set, so there is no way to exit a loop that is iterating over 
> the cursor. Below is the function code; it loops indefinitely when it is run.
> 
> create or replace function getxml() returns setof xml as $$
>     declare
>         resultxml xml;
>         curs refcursor;
>     begin
>         open curs for select * from groups;
>         loop
>             select cursor_to_xml(curs,1000, false, false, '') into resultxml;
>             return next resultxml;
>             exit when not found;
>         end loop;
>     end;
> $$ language plpgsql;

Yeah, there doesn't seem to be a good way out of that.  When the end of
the cursor is reached, cursor_to_xml returns an empty xml value (which
is probably bogus in itself, since that is not a valid xml value to
begin with), so you could test it like this:

exit when resultxml::text = '';

> 2) Assuming the above issue is fixed, how can I go about ensuring that the 
> result set from the function isn't stored in memory until the function 
> completes? Ideally, I'd like to write the output to a file with each 
> iteration of the cursor, but I know file IO is a big no-no with plpgsql since 
> transactions can't manage the state of files being written.

cursor_to_xml is more meant to be used from a client.  If you do it like
in the above function, you will indeed build the result in memory
(multiple times, perhaps).



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