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Re: Index Page Split logging

From: Martijn van Oosterhout <kleptog(at)svana(dot)org>
To: Simon Riggs <simon(at)2ndquadrant(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Index Page Split logging
Date: 2008-01-01 21:20:17
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Lists: pgsql-hackers
On Tue, Jan 01, 2008 at 08:55:58PM +0000, Simon Riggs wrote:
> On Tue, 2008-01-01 at 14:02 -0500, Tom Lane wrote:
> > Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> > > If we could log *only* the insert that caused the split, rather than the
> > > split itself, we would avoid that situation entirely.
> > 
> > How are you going to avoid the need to run user-defined functions
> > (specifically, the btree comparison functions) during replay?
> Seems like a good objection. Just exercising my lateral thought muscles.

It seems to me you should be able to manage an intermediate version
where (in for example GiST) you store the output of picksplit. i.e. you
describe your split as: items A,B,C went to the left and the rest went
to the right page. This would allow you to reconstruct the split
completely without actually having to write all the data.

The only thing I'm not sure about is whether it's easy to get the
relevent inforation to make this efficient.

Have a nice day,
Martijn van Oosterhout   <kleptog(at)svana(dot)org>
> Those who make peaceful revolution impossible will make violent revolution inevitable.
>  -- John F Kennedy

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