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Re: COPY Fillfactor patch

From: Neil Conway <neilc(at)samurai(dot)com>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: pgsql-patches(at)postgresql(dot)org
Subject: Re: COPY Fillfactor patch
Date: 2005-04-12 14:00:52
Message-ID: 425BD494.9000407@samurai.com (view raw or flat)
Thread:
Lists: pgsql-patches
Simon Riggs wrote:
> During recent tuning of the TPC-C workload, I produced the following
> patch to force COPY to leave some space in each data block when it loads
> data into heap relations.

I can't get too excited about incorporating changes designed solely to 
improve performance for the workload of a specific database benchmark. 
If the change has merit in some plausible "real world" situations, so be 
it -- but if not, I don't see the point.

> Each UPDATE tries to insert a new row version. The blocks are all full,
> so each UPDATE causes this activity:
> 	read block, decide cannot insert, unlock block
> 	extend relation by 1 block
> 	relock first block, lock new block
> 	insert row into new block
> After the patch, most UPDATEs cause only a single block access/update,
> excluding the index effects.

Did you do any benchmarks to measure the performance of the patch?

-Neil

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