Re: How does Index Scan get used

On Fri, 22 Feb 2002, Samuel J. Sutjiono wrote:

>  I tried an Index Scan but I kept on getting Seq Scan. Do you know why
> ? What do I need to do to get my query to use index scan (I tried to
> turn it on by doing SET ENABLE_indexscan = on; but it didn't work)
>
> create table test (test_col text);
> create index test_index on test (test_col);
> insert into test values ('abc.xyz');
> insert into test values ('abcxyz');
> insert into test values ('abc/xyz');
>
> explain select * from test where test_col like 'abc/%';
>
> NOTICE:  QUERY PLAN:
>
> Seq Scan on test  (cost=0.00..22.50 rows=10 width=12)
>
> Another question:
> Does Regex (~*) or like use table scan ?

It may, but IIRC only if you're running in 'C' locale (the
rule being used to make it indexable doesn't necessarily
work in other locales).