On Tue, 2006-05-02 at 14:02 +0200, Martijn van Oosterhout wrote:
> How about:
>
> SELECT id, get_category_text_path(id)
> FROM (SELECT id FROM category
> ORDER BY rank
> LIMIT 5) as x;
Oh that works? Great!
Let me see, with 'rank' from a joined table that looks like:
SELECT id, get_category_text_path(id), rank
FROM (
SELECT c.id
FROM category AS c
JOIN rank_lookup AS r ON r.cat_id = c.id
ORDER BY r.rank
LIMIT 5
) as x;
That works perfectly. It prevents a second join and thus solves the
question in my previous mail.
> Evidently you don't have an index on rank, otherwise it would've used
> the index to cut down on the number of rows that needed to be examined.
No, there is no index. I need to think about creating one...
Thank you very much.
Markus
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TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
