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From: wpp@marie.physik.tu-berlin.de (Kai Petzke)
Message-Id: <9501130040.AA07751@marie.physik.tu-berlin.de>
Subject: Re: POSTGRES Append Performance
To: smith_w@mcnc.org (William T. Smith)
Date: Fri, 13 Jan 1995 01:42:19 +0100 (MET)
Cc: postgres@postgres.Berkeley.EDU
In-Reply-To: <199501121907.OAA07712@robin.mcnc.org.mcnc.org> from "William T. Smith" at Jan 12, 95 02:07:47 pm
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Resent-To: postgres-redist@postgres.Berkeley.EDU
Resent-Date: Thu, 12 Jan 95 16:55:46 -0800
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> 
> Hello,
> 
> 	I am evaluating version 4.2 of POSTGRES as a database tool to
> provide persistent storage of directed graphs.  The test program adds
> one node which requires 17 append operations against an empty database.
> Each instance has less than 100 bytes.  The program takes 10 seconds
> elapsed time to execute.  Adding ten nodes takes 20 seconds.  Is this
> "normal" performance for POSTGRES?  Does anyone have any suggestions to
> improve performance? Is anyone using POSTGRES to support interactive
> applications.

Postgres has the overhead of all RDBMS systems: it has to parse the
queries, then optimize then, then do the actual work.  While doing
the first steps, tons of tuples are accessed from the pg_* files
of your database.

If you want better update performance for multiple tuples, use the 
"copy in" function.  Here, the parsing is done only once for the
complete set, not once for every datum.


Kai


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