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Re: performance for high-volume log insertion

From: Stephen Frost <sfrost(at)snowman(dot)net>
To: Ben Chobot <bench(at)silentmedia(dot)com>
Cc: david(at)lang(dot)hm, pgsql-performance(at)postgresql(dot)org
Subject: Re: performance for high-volume log insertion
Date: 2009-04-21 16:37:48
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Lists: pgsql-performance
* Ben Chobot (bench(at)silentmedia(dot)com) wrote:
> On Mon, 20 Apr 2009, david(at)lang(dot)hm wrote:
>> one huge advantage of putting the sql into the configuration is the 
>> ability to work around other users of the database.
> +1 on this. We've always found tools much easier to work with when they  
> could be adapted to our schema, as opposed to changing our process for 
> the tool.

I think we're all in agreement that we should allow the user to define
their schema and support loading the data into it.  The question has
been if the user really needs the flexibility to define arbitrary SQL to
be used to do the inserts.

Something I'm a bit confused about, still, is if this is really even a
problem.  It sounds like rsyslog already allows arbitrary SQL in the
config file with some kind of escape syntax for the variables.  Why not
just keep that, but split it into a prepared query (where you change the
variables to $NUM vars for the prepared statement) and an array of
values (to pass to PQexecPrepared)?

If you already know how to figure out what the variables in the
arbitrary SQL statement are, this shouldn't be any more limiting than
today, except where a prepared query can't have a variable argument but
a non-prepared query can (eg, table name).  You could deal with that
with some kind of configuration variable that lets the user choose to
use prepared queries or not though, or some additional syntax that
indicates certain variables shouldn't be translated to $NUM vars (eg:
$*blah instead of $blah).



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