Re: Benchmark Data requested

From: Simon Riggs <simon(at)2ndquadrant(dot)com>
To: Richard Huxton <dev(at)archonet(dot)com>
Cc: Dimitri Fontaine <dfontaine(at)hi-media(dot)com>, pgsql-performance(at)postgresql(dot)org, "Jignesh K(dot) Shah" <J(dot)K(dot)Shah(at)sun(dot)com>, Greg Smith <gsmith(at)gregsmith(dot)com>
Subject: Re: Benchmark Data requested
Date: 2008-02-05 14:54:28
Message-ID: 1202223268.4252.707.camel@ebony.site
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On Tue, 2008-02-05 at 14:43 +0000, Richard Huxton wrote:
> Simon Riggs wrote:
> > On Tue, 2008-02-05 at 15:06 +0100, Dimitri Fontaine wrote:
> >>
> >> Le lundi 04 février 2008, Jignesh K. Shah a écrit :
>
> >>> Multiple table loads ( 1 per table) spawned via script is bit better
> >>> but hits wal problems.
> >> pgloader will too hit the WAL problem, but it still may have its benefits, or
> >> at least we will soon (you can already if you take it from CVS) be able to
> >> measure if the parallel loading at the client side is a good idea perf. wise.
> >
> > Should be able to reduce lock contention, but not overall WAL volume.
>
> In the case of a bulk upload to an empty table (or partition?) could you
> not optimise the WAL away? That is, shouldn't the WAL basically be a
> simple transformation of the on-disk blocks? You'd have to explicitly
> sync the file(s) for the table/indexes of course, and you'd need some
> work-around for WAL shipping, but it might be worth it for you chaps
> with large imports.

Only by locking the table, which serializes access, which then slows you
down or at least restricts other options. Plus if you use pg_loader then
you'll find only the first few rows optimized and all the rest not.

--
Simon Riggs
2ndQuadrant http://www.2ndQuadrant.com

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