Re: index theory

On Wed, 2002-10-16 at 09:19, Karel Zak wrote:
>
> Hi,
>
> I have SQL query:
>
> SELECT * FROM ii WHERE i1='a' AND i2='b';
>
> There're indexes on i1 and i2. I know best solution is use one
> index on both (i1, i2).
>
> The EXPLAIN command show that optimalizer wants to use one index:
>
> test=# explain SELECT * FROM ii WHERE i1='a' AND i1='b';
> QUERY PLAN
> ---------------------------------------------------------------------------------
> Index Scan using i1 on ii (cost=0.00..4.83 rows=1 width=24)
> Index Cond: ((i1 = 'a'::character varying) AND (i1 = 'b'::character varying))

I think you typo'd. i1='a' AND i1='b' turns into 'a' = 'b' which
certainly isn't true in any alphabets I know of.

--
Rod Taylor