From: Achilleus Mantzios <achill@matrix.gatewaynet.com>
To: Greg Stark <gsstark@mit.edu>
Cc: pgsql-sql <pgsql-sql@postgresql.org>
Subject: Re: Gist indexes on int arrays
Date: Tue, 4 Mar 2003 18:57:23 -0200 (GMT+2)
Message-ID: <Pine.LNX.4.44.0303041751190.31970-100000@matrix.gatewaynet.com> (raw)
In-Reply-To: <87smu3kv7d.fsf@stark.dyndns.tv>
On 4 Mar 2003, Greg Stark wrote:
>
> Achilleus Mantzios <achill@matrix.gatewaynet.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".
>
> 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
>
--
==================================================================
Achilleus Mantzios
S/W Engineer
IT dept
Dynacom Tankers Mngmt
Nikis 4, Glyfada
Athens 16610
Greece
tel: +30-210-8981112
fax: +30-210-8981877
email: achill@matrix.gatewaynet.com
mantzios@softlab.ece.ntua.gr
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To: pgsql-sql@postgresql.org
Cc: achill@matrix.gatewaynet.com, gsstark@mit.edu
Subject: Re: Gist indexes on int arrays
In-Reply-To: <Pine.LNX.4.44.0303041751190.31970-100000@matrix.gatewaynet.com>
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