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@ontko.com  Phone 1.765.935.4283  Fax 1.765.962.9788
>Ray Ontko & Co.     Software Consulting Services     http://www.ontko.com/
>
>