Re: Returning multiple Rows from PL/pgSQL-Function

From: "Alvar Freude" <alvar@agi.de>

> Hi,
>
> I want to create a function (PL/pgSQL), which return multiple rows. But it
> fails -- when Creating the function, I get a notice:

> How should I do this?

Can't at the moment.

> or, in more detail the exact function:
>
>
>    CREATE FUNCTION get_emotions (timestamp) RETURNS SETOF records AS
>          '
>          DECLARE
>             start ALIAS FOR $1;
>             end_id int4;
>          BEGIN
>             SELECT emotion_id FROM emotions
>                              WHERE date <= start
>                              LIMIT 1
>                               INTO end_id;

Not entirely clear what your function is for, but the above select looks a
bit odd. Do you not want to "order by" here so you can get the "most recent"
emotion_id or whatever?

>             RETURN SELECT emotion_id, emotion1, [...]
>                   FROM  emotions
>                   WHERE emotion_id BETWEEN end_id-3000 AND end_id
>                   ORDER BY date_epoch + full_rating*(3600*12)
>                   LIMIT 300;
>          END;
>          '
>       LANGUAGE 'plpgsql';

I'd rewrite this as just a select, or a view if you want to keep things
clean in the application, possibly with that first select encapsulated in a
function (sorry, I'm not entirely clear what your code is doing).

so:

CREATE VIEW get_emotions_view AS
SELECT emotion_id, emotion1, ...
ORDER BY date_epoch + full_rating*3600*12
LIMIT 300;

and then issue a query like:

SELECT * FROM get_emotions view
WHERE emotion_id
BETWEEN last_em_id(<start val here>)-3000 AND last_em_id(<start val here>);

If you set the "is_cachable" flag on the last_em_id() function it should
only be calculated once.

HTH

- Richard Huxton