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Re: simple join uses indexes, very slow

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$59ccd870$ (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
> -----Original Message-----
> From: pgsql-performance-owner(at)postgresql(dot)org
> 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
> > opset_num even though opset_num is indexed. Isn't Postgres able to
> the
> > index instead of sorting?
> The time of an index scan vs. a sequential scan + sort depends on
> factors, so it's not just a matter of walking the index whenever there
> 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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