| From: | Josh Berkus <josh(at)agliodbs(dot)com> |
|---|---|
| To: | pgsql-performance(at)postgresql(dot)org |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Gabriele Bartolini <angusgb(at)tin(dot)it>, "Aaron Werman" <awerman2(at)hotmail(dot)com> |
| Subject: | Re: Data warehousing requirements |
| Date: | 2004-10-08 05:53:26 |
| Message-ID: | 200410072253.26169.josh@agliodbs.com |
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| Lists: | pgsql-performance |
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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