Re: Data warehousing requirements

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От Josh Berkus
Тема Re: Data warehousing requirements
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Msg-id 200410072253.26169.josh@agliodbs.com
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Ответ на Re: Data warehousing requirements  (Tom Lane <tgl@sss.pgh.pa.us>)
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Tom,

Well, I sit corrected.   Obviously I misread that.

> It's not so much that they are necessarily inefficient as that they
> constrain the planner's freedom of action.  You need to think a lot more
> carefully about the order of joining than when you use inner joins.

I've also found that OUTER JOINS constrain the types of joins that can/will be
used as well as the order.  Maybe you didn't intend it that way, but (for
example) OUTER JOINs seem much more likely to use expensive merge joins.

--
Josh Berkus
Aglio Database Solutions
San Francisco

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