Re: [HACKERS] indexing words slow

On Wed, 11 Mar 1998, Bruce Momjian wrote:

> >
> > > On the other hand, if I do a count(*) on '^ric', his takes consequently
> > > around 1:30 mins, no matter how often I run it. This returns 7866.
> > >
> > > A search on count(*) of '^lling' and '^tones' takes around 2.5 secs after
> > > running it several times.
> >
> > Since postgres will still read the data row (even for this count(*)) I would guess,
> > that this is a data distribution problem. Maybe you could cluster your data ?
> > Maybe the '^rol' rows stick pretty much together, whilst the '^ric' rows
> > are evenly distributed on all datapages. Of course there would be room
> > for improvement if postgresql would not read the data pages, which are not needed
> > for any query that only selects columns that are part of the index.
> >
>
> Brilliant.  I had forgotten that the data pages are accessed as well as
> the index pages.  The CLUSTER command works in 6.3, so perhaps that will
> change some times.

Running a 'cluster' right now....

Maarten

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| TU Delft, The Netherlands, Faculty of Information Technology and Systems  |
|                   Department of Electrical Engineering                    |
|           Computer Architecture and Digital Technique section             |
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