Re: Why is it not using an index?

Really, the PostgreSQL interpreter should be smart enough to figure this
out by itself...


Gregory Wood wrote:
>
> > explain select * from a where x=3;
>
> PostgreSQL is treating 3 as an int4 (integer) type, whereas x is an int2
> (smallint) type. Try casting the constant as a smallint and it should use
> the index:
>
> explain select * from a where x=3::smallint;
>
> Greg
>
> ----- Original Message -----
> From: "Dmitry Tkach" <dmitry@openratings.com>
> To: <pgsql-general@postgresql.org.pgsql-sql@postgresql.org>
> Sent: Friday, March 15, 2002 2:07 PM
> Subject: [GENERAL] Why is it not using an index?
>
> > This must be really simple, but I just can't get it :-(
> > I have a table (a) with a single column (x):
> >
> >            Table "a"
> >   Attribute |   Type   | Modifier
> > -----------+----------+----------
> >   x         | smallint |
> > Index: a_idx
> >
> >
> >     Index "a_idx"
> >   Attribute |   Type
> > -----------+----------
> >   x         | smallint
> > btree
> >
> > The table has 10000000 rows....
> >
> > Now, how come, when I do:
> >
> > explain select * from a where x=3;
> >
> > it says:
> >
> > Seq Scan on bset  (cost=100000000.00..100175934.05 rows=303 width=2)
> >
> > Why is it not using a_idx???
> >
> > I even tried set enable_seqscan to off - makes no difference :-(
> >
> > Any idea what is going on?
> >
> > Thanks a lot!
> >
> > Dima
> >
> >
> > ---------------------------(end of broadcast)---------------------------
> > TIP 5: Have you checked our extensive FAQ?
> >
> > http://www.postgresql.org/users-lounge/docs/faq.html
> >
>
> ---------------------------(end of broadcast)---------------------------
> TIP 5: Have you checked our extensive FAQ?
>
> http://www.postgresql.org/users-lounge/docs/faq.html