| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: add_path optimization |
| Date: | 2009-02-03 15:54:14 |
| Message-ID: | 603c8f070902030754s68806da4xfe884aec454291b8@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Feb 3, 2009 at 10:17 AM, Kevin Grittner
<Kevin(dot)Grittner(at)wicourts(dot)gov> wrote:
>> We're going to need to see the test case, because I don't see that in
>> some simple tests here.
> Plans from 8.3.5 and 8.4devel attached.
>
> If you need something else, let me know.
I had a suspicion we were going to see something like this. You're
using several NOT EXISTS clauses and 8.4devel is converting those into
Anti Joins. Aside from the longer planning time, the resulting plan
appears to have a much higher estimated cost, so I'm suspicious of a
bug in the new Semi/Anti join stuff, but I don't have time to track it
down right now (and I suspect Tom will figure it out faster than I can
anyway).
...Robert
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