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Re: Decreasing WAL size effects

From: Kyle Cordes <kyle(at)kylecordes(dot)com>
To: pgsql <pgsql-general(at)postgresql(dot)org>
Subject: Re: Decreasing WAL size effects
Date: 2008-10-30 21:16:43
Message-ID: 490A243B.2030907@kylecordes.com (view raw or flat)
Thread:
Lists: pgsql-generalpgsql-hackers
Greg Smith wrote:
> On Thu, 30 Oct 2008, Kyle Cordes wrote:
> 
>> It sure would be nice if there was a way for PG itself to zero the 
>> unused portion of logs as they are completed, perhaps this will make 


> The overhead of clearing out the whole thing is just large enough that 
> it can be disruptive on systems generating lots of WAL traffic, so you 

Hmm.  My understanding is that it wouldn't need to clear out the whole 
thing, just the unused portion at the end. This wouldn't add any 
initialize effort at startup / segment creation at all, right?  The 
unused portions at the end only happen when a WAL segment needs to be 
finished "early" for some reason.  I'd expect in a heavily loaded 
system, that PG would be filling each segment, not ending them early.

However, there could easily be some reason that I am not familiar with, 
that would cause a busy PG to nonetheless end a lot of segments early.

-- 
Kyle Cordes
http://kylecordes.com

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