On Mon, 13 Jun 2005, Tom Lane wrote:
Teodor Sigaev <[EMAIL PROTECTED]> 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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Oleg
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Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg@sai.msu.su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83
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