Hi,
PostgreSQL 6.5.3.
I've created the following index:
>create index test_index on test (filed1);
>vacuum;
And then:
>explain select field1 from test group by field1;
NOTICE: QUERY PLAN:
Group (cost=2510.40 rows=58709 width=12) -> Sort (cost=2510.40 rows=58709 width=12) -> Seq Scan on test
(cost=2510.40rows=58709 width=12)
It don't use this index :-(. I've tried to create two types of index:
b-tree and hash - both doesn't work until "group" is present. If I type
> explain select field1 from test where field1='tra-ta-ta';
NOTICE: QUERY PLAN:
Index Scan using test_index on test (cost=2.05 rows=2 width=12)
It work this way.
Any ideas?
_____________
Vlad Marchenko