Re: Need help - optimizer trouble

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От Helge Bahmann
Тема Re: Need help - optimizer trouble
Дата
Msg-id Pine.LNX.4.21.0104051330550.21299-100000@lothlorien.stunet2.tu-freiberg.de
обсуждение исходный текст
Ответ на Re: Need help - optimizer trouble  (Tom Lane <tgl@sss.pgh.pa.us>)
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On Wed, 4 Apr 2001, Tom Lane wrote:
> 7.1 treats the JOIN clauses as determining join order, where 7.0 did
> not.  Looks like you should re-order the query to be, say,
>
> SELECT doc FROM written_by AS wb
>     JOIN author_keyword AS kw ON kw.author_id=wb.author_id
>     JOIN document ON document.doc_id=wb.doc_id
>     WHERE kw.keyword='foo'

It works! I restructured my query

SELECT doc FROM document
    JOIN (SELECT keyword, doc_id FROM written_by AS _w
        JOIN author_keyword AS _kw ON _w.author_id=_kw.author_id
    ) AS wb ON document.doc_id=wb.doc_id
    WHERE wb.keyword='foo'

which is easier to handle for my application logic and it is pretty fast
now.

Many thanks for your help!

regards,
Helge


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