Re: Missed index opportunity for outer join? - Mailing list pgsql-performance

From Tom Lane
Subject Re: Missed index opportunity for outer join?
Date
Msg-id 4678.1133888239@sss.pgh.pa.us
Whole thread Raw
In response to Re: Missed index opportunity for outer join?  (rm_pg@cheapcomplexdevices.com)
Responses Re: Missed index opportunity for outer join?  (Ron Mayer <rm_pg@cheapcomplexdevices.com>)
List pgsql-performance
rm_pg@cheapcomplexdevices.com writes:
> On Mon, 5 Dec 2005, Tom Lane wrote:
>> (Note to self: it is a bit odd that fac_id=261 is pushed down to become
>> an indexqual in one case but not the other ...)

> I speculate that the seq_scan wasn't really the slow part
> compared to not using using both parts of the index in the
> second part of the plan.  The table point_features is tens of
> thousands of rows, while the table facets is tens of millions.

Agreed, but it's still odd that it would use a seqscan in one case and
not the other.

I found the reason why the fac_id=261 clause isn't getting used as an
index qual; it's a bit of excessive paranoia that goes back to 2002.
I've fixed that for 8.1.1, but am still wondering about the seqscan
on the other side of the join.

            regards, tom lane

pgsql-performance by date:

Previous
From: Joshua Kramer
Date:
Subject: TSearch2 vs. Apache Lucene
Next
From: Michael Riess
Date:
Subject: Re: TSearch2 vs. Apache Lucene