From: Pierre C <lists@peufeu.com>
To: Andy Colson <andy@squeakycode.net>
To: Dan Schaffer <Daniel.S.Schaffer@noaa.gov>
Cc: Jim Nasby <jim@nasby.net>
Cc: pgsql-performance@postgresql.org, "Nick Matheson" <Nick.D.Matheson@noaa.gov>
Subject: Re: Help with bulk read performance
Date: Thu, 16 Dec 2010 16:22:40 +0100
Message-ID: <op.vntbn2ujeorkce@apollo13> (raw)
In-Reply-To: <4D0921D2.2030806@noaa.gov>
References: <4CCECB69.7080906@noaa.gov>
<4D078CD7.7030308@squeakycode.net>
<B57C829F-DFE3-4DC7-877B-14D5B05AB4BB@nasby.net>
<4D07928B.2070907@squeakycode.net>
<4D0921D2.2030806@noaa.gov>
> If the data are stored as a byte array but retrieve into a ResultSet,
> the unpacking time goes up by an order of magnitude and the
> observed total throughput is 25 MB/s. If the data are stored in a
> Postgres float array and unpacked into a byte stream, the
> observed throughput is 20 MB/s.
float <-> text conversions are very slow, this is in fact due to the
mismatch between base-2 (IEEE754) and base-10 (text) floating point
representation, which needs very very complex calculations.
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To: pgsql-performance@postgresql.org
Cc: lists@peufeu.com, andy@squeakycode.net, Daniel.S.Schaffer@noaa.gov, jim@nasby.net, Nick.D.Matheson@noaa.gov
Subject: Re: Help with bulk read performance
In-Reply-To: <op.vntbn2ujeorkce@apollo13>
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