Re: How does Index Scan get used

On Fri, 2002-02-22 at 14:46, 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)

PostgreSQL thinks there are only 10 rows in the table. Therefore it
will not choose an index scan because for so few rows it is bound to be
more expensive than a sequential scan.

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Oliver Elphick Oliver(dot)Elphick(at)lfix(dot)co(dot)uk
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