Re: GiST: PickSplit and multi-attr indexes

Neil,

I think we should not touch this right now unless you certainly know
algorithm proven to be good in general case. Did you already got some idea ?
    Oleg

On Mon, 15 Nov 2004, Neil Conway wrote:

> On Sun, 2004-11-14 at 18:54 -0500, Tom Lane wrote:
>> It's probably just a hangover from the days when GiST didn't support
>> multi-column indexes at all.  I agree it should be changed.
>
> I'm not sure the right way to fix it (at least without significant
> changes to the GiST API). At present, the PickSplit() method is passed a
> vector of GISTENTRYs and fills in a GIST_SPLITVEC. The GISTENTRYs
> correspond to the first attributes of all the tuples in the node to be
> split. There is no provision for the GiST extension to be informed about
> any additional attributes in the index tuples. Even if we changed the
> API to allow that, the GiST extension would have a hard time making a
> reasonable decision in the multi-attribute case: the additional index
> attributes could well be implemented using a different GiST extension.
>
>> But note you will then have to cope with NULL values.
>
> Yes -- I'm not sure offhand why GiST does not allow leading NULL values
> in index attributes, but that ought to be fixed anyway.
>
> -Neil
>
>
>
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    Regards,        Oleg
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Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
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