From: | "Dave Dutcher" <dave(at)tridecap(dot)com> |
---|---|
To: | "'Steinar H(dot) Gunderson'" <sgunderson(at)bigfoot(dot)com>, <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: simple join uses indexes, very slow |
Date: | 2006-03-29 01:30:23 |
Message-ID: | 010a01c652d0$59ccd870$8300a8c0@tridecap.com |
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Lists: | pgsql-performance |
> -----Original Message-----
> From: pgsql-performance-owner(at)postgresql(dot)org
[mailto:pgsql-performance-
> owner(at)postgresql(dot)org] On Behalf Of Steinar H. Gunderson
> A merge join requires sorted inputs.
>
> > Most of the time was spent sorting the parameters parameters table
by
> > opset_num even though opset_num is indexed. Isn't Postgres able to
walk
> the
> > index instead of sorting?
>
> The time of an index scan vs. a sequential scan + sort depends on
several
> factors, so it's not just a matter of walking the index whenever there
is
> one.
I was just looking this over again and I realized I misread the query
plan. The slowest step was the Bitmap Heap Scan not the sort. (The
sort was relatively fast.)
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