Обсуждение: Strange indexing

Hi!

is this OK.

CREATE TABLE test (
id int primary key,
name varchar(255),
parent varchar(32)
);


If i write

explain select * from test where id=1;

This is output of 1st table:
Index Scan using test_pkey on test  (cost=0.00..4.82 rows=1 width=183)


but the i create index on parent like this

create index tt on test (parent);

And when i execute query

explain select * from test where parent = '1';

Seq Scan on test  (cost=0.00..1.07 rows=1 width=17)

Why i there no index scan if i create index. I also run
vacuum on this table.


both queryes return only 1 row.



--
bye,
 Uros                          mailto:uros@sir-mag.com

Uros Gruber <uros@sir-mag.com> writes:
> explain select * from test where parent = '1';
> Seq Scan on test  (cost=0.00..1.07 rows=1 width=17)

> Why i there no index scan if i create index. I also run
> vacuum on this table.

After the vacuum, the planner knows that your table is too small to
bother with an indexscan.  Try putting in a more realistic amount of
data.

            regards, tom lane