Re: Gist indexes on int arrays

On Tue, 4 Mar 2003, Achilleus Mantzios wrote:

> On 4 Mar 2003, Greg Stark wrote:
>
> >
> > Achilleus Mantzios <achill(at)matrix(dot)gatewaynet(dot)com> writes:
> >
> > > Moreover if your array element positions that you want to compare
> > > against(e.g attr_a[1], or attr_b[n], where n is the last element) are
> > > known, then you could have a function "first" that returns
> > > the first element ...
> >
> > Except that's precisely what I'm *not* doing. I'm treating the arrays as sets
> > and looking for records where the set contains a given value. This is a
> > denormalized table generated nightly from fully normalized raw data.
> >
> > So to simplify it, the query might have clauses like:
> >
> > WHERE foo_id = 900
> > AND '{5}'::integer[] ~ attribute_set_array
> >
> > Right now I have a btree index on (foo_id).
> >
> > Can I have a GiST index on (foo_id, attribute_set_array) and have it be just
> > as fast at narrowing the search to just foo_id = 900 but also speed up the ~
> > operation?
>
> I am afraid you cant do that easily. (but you can follow recent
> discussions on the matter).
> int4 does not have an opclass that can cope with "gist".

no-no, just use contrib/btree_gist !

>
> >
> > Incidentally, it seems odd that there isn't an operator like ~ but optimized
> > specifically for searching for a single item. It seems awkward and possibly
> > unnecessarily slow to have to construct an array for the search parameter
> > every time.
> >
>
> What do you mean by "slow"?
>
> > --
> > greg
> >
>
>

Regards,
Oleg
_____________________________________________________________
Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
Sternberg Astronomical Institute, Moscow University (Russia)
Internet: oleg(at)sai(dot)msu(dot)su, http://www.sai.msu.su/~megera/
phone: +007(095)939-16-83, +007(095)939-23-83