Re: Best way to scan on-disk bitmaps

On Mon, 13 Jun 2005, Tom Lane wrote:

> Teodor Sigaev <teodor@sigaev.ru> wrote:
>> ... So, if index is defined as 'using gist (a,b,c)' then, in
>> principle, GiST index can speed up queries like 'a=V1 and c=V2'.  But
>> it will not usable for queries ( b=V3 and c=V2 ). By the way, instead
>> of '=' operation may be used other operations. Number of supported
>> operations by GiST is indefinite unlike, for example, btree which
>> supported only five: <, <=, =, =>, >.
>
> I have committed changes to the planner to arrange that a GiST indexscan
> must supply at least one restriction clause for the first index column,
> and can supply restriction clauses for any, all, or none of the
> remaining columns; the old left-to-right heuristic is gone.
>
> As far as I can tell, this doesn't require any changes to the GiST code,
> but please take another look if you aren't too sure about it.

I did quick test and found no problem with gist(a,b,c) and index does used for 
(a,*,c) case

>
>             regards, tom lane
>
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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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