Re: Resources

Sorry, I made too general a statement. Index will help when the expession
is anchored to beginning of field. So 'A%' gets help from index, but '%A%'
does not.

Frank

At 11:13 AM 1/11/02 -0500, Nick Fankhauser wrote:
>
>> I don't beleive indexes will improve SELECT using LIKE.
>
>I wondered about that too, so I did a test using a database I'm working
>with. The results indicate that it helps substantially- here is my terminal
>log file:
>
>staging=#
>staging=#
>staging=# explain select count(*) from actor where actor_full_name like
>'A%';
>NOTICE: QUERY PLAN:
>
>Aggregate (cost=1067.72..1067.72 rows=1 width=0)
> -> Seq Scan on actor (cost=0.00..1066.29 rows=572 width=0)
>
>EXPLAIN
>staging=# create index test on actor(actor_full_name);
>CREATE
>staging=# explain select count(*) from actor where actor_full_name like
>'A%';
>NOTICE: QUERY PLAN:
>
>Aggregate (cost=577.46..577.46 rows=1 width=0)
> -> Index Scan using test on actor (cost=0.00..576.03 rows=572 width=0)
>
>EXPLAIN
>staging=#
>
>
>-Nick
>
>--------------------------------------------------------------------------
>Nick Fankhauser nickf(at)ontko(dot)com Phone 1.765.935.4283 Fax 1.765.962.9788
>Ray Ontko & Co. Software Consulting Services http://www.ontko.com/
>
>