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Re: Understanding tsearch2 performance

From: Oleg Bartunov <oleg(at)sai(dot)msu(dot)su>
To: Ivan Voras <ivoras(at)freebsd(dot)org>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Understanding tsearch2 performance
Date: 2010-07-14 13:25:27
Message-ID: Pine.LNX.4.64.1007141722480.32129@sn.sai.msu.ru (view raw or flat)
Thread:
Lists: pgsql-performance
On Wed, 14 Jul 2010, Ivan Voras wrote:

>> Returning 8449 rows could be quite long.
>
> You are right, I didn't test this. Issuing a query which returns a
> smaller result set is much faster.
>
> But, offtopic, why would returning 8500 records, each around 100 bytes
> long so around 8.5 MB, over local unix sockets, be so slow? The machine
> in question has a sustained memory bendwidth of nearly 10 GB/s. Does
> PostgreSQL spend much time marshalling the data through the socket stream?

It's disk access time.
in the very bad case it could take  ~5 ms (for fast drive) to get one just
one row.


 	Regards,
 		Oleg
_____________________________________________________________
Oleg Bartunov, Research Scientist, Head of AstroNet (www.astronet.ru),
Sternberg Astronomical Institute, Moscow University, Russia
Internet: oleg(at)sai(dot)msu(dot)su, http://www.sai.msu.su/~megera/
phone: +007(495)939-16-83, +007(495)939-23-83

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