Re: Factoring where clauses through unions

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От Ed L.
Тема Re: Factoring where clauses through unions
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Msg-id 200304041656.34153.pgsql@bluepolka.net
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Ответ на Re: Factoring where clauses through unions  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: Factoring where clauses through unions
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On Friday April 4 2003 4:41, Tom Lane wrote:
> "Ed L." <pgsql@bluepolka.net> writes:
> > On Friday April 4 2003 1:42, Jonathan Bartlett wrote:
> >> I have a view that is based on several UNION clauses.  I'm wondering,
> >> if I select data from there, will it UNION first, and then apply my
> >> where clauses, or can it factor my where clauses through the UNION?
> >> If it doesn't do it automatically, is there any way to automate it?
> >
> > For cases like this, you can usually construct a very simple test to
> > get the answer.
>
> A test case would tell him what the version he tests does.  It would not
> likely inform him that 7.3 will push down such conditions but prior
> versions don't ...

Can you provide a simple example of this change between 7.2.x and 7.3?

Ed


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