Re: [HACKERS] Index creation takes for ever

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Manfred Koizar <mkoi-pg(at)aon(dot)at>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-patches(at)postgresql(dot)org, ohp(at)pyrenet(dot)fr, pgsql-hackers list <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [HACKERS] Index creation takes for ever
Date: 2004-03-17 01:23:09
Message-ID: 200403170123.i2H1N9H10786@candle.pha.pa.us
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Where are we on this? It seems like a win to me.

---------------------------------------------------------------------------

Manfred Koizar wrote:
> On Mon, 01 Dec 2003 13:32:10 -0500, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >Manfred Koizar <mkoi-pg(at)aon(dot)at> writes:
> >> comparetup_index() compares two IndexTuples. The structure
> >> IndexTupleData consists basically of not much more than an ItemPointer,
> >> and the patch is not much more than adding a comparison of two
> >> ItemPointers. So how does the patch introduce a new low level
> >> implementation dependency?
> >
> >Because it sorts on tuple position, which is certainly about as low
> >level as you can get.
>
> The patch affects only the sort during index creation. Mapping key
> values to tuple positions is the sole purpose of an index. The notion
> that an index should not care for tuple positions looks a bit strange to
> me.
>
> > More to the point, though, no evidence has been
> >provided that this is a good idea.
>
> The test script I posted with the patch shows that the patch produces
> more efficient b-tree indices when there are lots of duplicates.
>
> Servus
> Manfred
>
> ---------------------------(end of broadcast)---------------------------
> TIP 4: Don't 'kill -9' the postmaster
>

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