Re: Question about explain of index scan - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Question about explain of index scan
Date
Msg-id 14586.1125675109@sss.pgh.pa.us
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In response to Re: Question about explain of index scan  (Hannu Krosing <hannu@skype.net>)
List pgsql-hackers
Hannu Krosing <hannu@skype.net> writes:
> On R, 2005-09-02 at 10:31 -0400, Tom Lane wrote:
>> Yes.  However, I don't understand how you got that result; AFAIK the
>> planner should have eliminated the duplicate subclauses.

> the query was similar to this:
> [snip]

Oh, the OR arms are actually *not* equivalent because of the log_tableid
subclauses.  So that explains why canonicalize_qual() didn't eliminate
them.

[ experiments... ]  It looks like 8.0 and up are smart enough to
consolidate the identical extracted indexquals, but not 7.4.
        regards, tom lane


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