Re: select using an index

Pau Marc Munoz Torres írta:
> Hi
>
> Recently i created an index in a table using a function (not a
> column) as following
>
> create index H2IAb on precalc (idr(p1,p4,p6,p7,p9,'H-2*IAb'));,
>
> where idr is a function that returns a real number,
>
> as a result i got the following table
>
> mhc2db=> \d precalc;
> Table "public.precalc"
> Column | Type | Modifiers
> -------------+-------------------+------------------------------------------------------
>
> id | integer | not null default
> nextval('precalc_id_seq'::regclass)
> p1 | character(1) |
> p4 | character(1) |
> p6 | character(1) |
> p7 | character(1) |
> p9 | character(1) |
> Indexes:
> "h2iab" btree (idr(p1, p4, p6, p7, p9, 'H-2*IAb'::character varying)),
>
> now, i would like to perform a query using this index, something like
>
>
> Select * from precalc where h2iab>2
>
> but obviously h2iab is not a column...
>
> some of you knows what i should do?
>
> thanks

Formulate your WHERE clause so it matches
your index's expression. E.g.

SELECT * FROM precalc WHERE
idr(p1, p4, p6, p7, p9, 'H-2*IAb'::character varying) > 2;

Best regards,
Zoltán Böszörményi

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Zoltán Böszörményi
Cybertec Schönig & Schönig GmbH
http://www.postgresql.at/