Re: ...WHERE TRUE" condition in union results in bad query pla

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От Tom Lane
Тема Re: ...WHERE TRUE" condition in union results in bad query pla
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Msg-id 7810.1333467334@sss.pgh.pa.us
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Ответ на Re: ...WHERE TRUE" condition in union results in bad query pla  (Robert Haas <robertmhaas@gmail.com>)
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Robert Haas <robertmhaas@gmail.com> writes:
> On Sat, Mar 3, 2012 at 10:03 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Sooner or later I'd like to relax the restriction that appendrel members
>> can't have extra WHERE clauses, but don't hold your breath waiting...

> Does this comment need updating?

>  * Note: the data structure assumes that append-rel members are single
>  * baserels.  This is OK for inheritance, but it prevents us from pulling
>  * up a UNION ALL member subquery if it contains a join.  While that could
>  * be fixed with a more complex data structure, at present there's not much
>  * point because no improvement in the plan could result.

No, that's a different restriction.

            regards, tom lane

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