Re: Guesses on what this NestLoop is for?

On Mon, 27 Oct 2003 15:32:41 -0800, Josh Berkus <josh(at)agliodbs(dot)com>
wrote:
>FROM event_types, events
> LEFT OUTER JOIN ...
>WHERE events.status = 1 or events.status = 11
> and events.event_date > '2003-10-27'
> and events.etype_id = event_types.etype_id
> and ( ...
> );
>
>
>What I can't figure out is what is that inredibly expensive nested loop for?

Sorry, I have no answer to your question, but may I ask whether you
really want to get presumably 106 output rows for each event with
status 1?

Or did you mean
WHERE (events.status = 1 OR events.status = 11) AND ...

>Ideas?

I'd also try to push that NOT EXISTS condition into the FROM clause:

...LEFT JOIN (SELECT DISTINCT ON (event_id)
event_id, mod_date, mod_user
FROM event_history
ORDER BY event_id, mod_date
) AS eh ON (events.event_id = eh.event_id) ...
WHERE ...
AND CASE WHEN eh.event_id IS NULL
THEN events.mod_user
ELSE eh.mod_user END = 562

If mod_user is NOT NULL in event_history, then CASE ... END can be
simplified to COALESCE(eh.mod_user, events.mod_user).

Servus
Manfred