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Date: Fri, 20 Jan 2006 22:37:54 +0100
From: Martijn van Oosterhout <kleptog@svana.org>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Stephan Vollmer <svollmer@gmx.de>, pgsql-performance@postgreSQL.org
Subject: Re: [GENERAL] Creation of tsearch2 index is very slow
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On Fri, Jan 20, 2006 at 04:19:15PM -0500, Tom Lane wrote:
>   %   cumulative   self              self     total          =20
>  time   seconds   seconds    calls  Ks/call  Ks/call  name   =20
>  98.96   1495.93  1495.93 33035195     0.00     0.00  hemdistsign

<snip>

> So we gotta fix hemdistsign ...

lol! Yeah, I guess so. Pretty nasty loop. LOOPBIT will iterate 8*63=3D504
times and it's going to do silly bit handling on each and every
iteration.

Given that all it's doing is counting bits, a simple fix would be to
loop over bytes, use XOR and count ones. For extreme speedup create a
lookup table with 256 entries to give you the answer straight away...

Have a nice day,
--=20
Martijn van Oosterhout   <kleptog@svana.org>   http://svana.org/kleptog/
> Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a
> tool for doing 5% of the work and then sitting around waiting for someone
> else to do the other 95% so you can sue them.

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