Re: Why isn't this index being used?

Hi, I ran into a similar problem using bigints...

See:
http://www.postgresql.org/docs/7.3/static/datatype.html#DATATYPE-INT

small & big int have to be cast when used in querries... try:
explain select * from db where type=90::smallint and
subtype=70::smallint and date='7/1/2004';
or
explain select * from db where type='90' and subtype='70' and
date='7/1/2004';

Knutsen, Mark wrote:

> The following is from a database of several hundred million rows of
> real data that has been VACUUM ANALYZEd.
>
>
>
> Why isn't the index being used for a query that seems tailor-made for
> it? The results (6,300 rows) take about ten minutes to retrieve with a
> sequential scan.
>
>
>
> A copy of this database with "integer" in place of "smallint", a
> primary key in column order (date, time, type, subtype) and a
> secondary index in the required order (type, subtype, date, time)
> correctly uses the secondary index to return results in under a second.
>
>
>
> Actually, the integer version is the first one I made, and the
> smallint is the copy, but that shouldn't matter.
>
>
>
> Postgres is version "postgresql-server-7.3.4-3.rhl9" from Red Hat Linux 9.
>
>
>
> =====
>
>
>
> testdb2=# \d db
>
>               Table "public.db"
>
>  Column  |          Type          | Modifiers
>
> ---------+------------------------+-----------
>
>  date    | date                   | not null
>
>  time    | time without time zone | not null
>
>  type    | smallint               | not null
>
>  subtype | smallint               | not null
>
>  value   | integer                |
>
> Indexes: db_pkey primary key btree ("type", subtype, date, "time")
>
>
>
> testdb2=# set enable_seqscan to off;
>
> SET
>
>
>
> testdb2=# explain select * from db where type=90 and subtype=70 and
> date='7/1/2004';
>
>                                   QUERY PLAN
>
> ------------------------------------------------------------------------------
>
>  Seq Scan on db  (cost=100000000.00..107455603.76 rows=178 width=20)
>
>    Filter: (("type" = 90) AND (subtype = 70) AND (date =
> '2004-07-01'::date))
>
> (2 rows)
>