Re: index not used if using IN or OR

Mario Ivankovits <mario(at)ops(dot)co(dot)at> writes:
> After populating the table with 8920 records and "analyze" the scenario
> gets even worser:

> select * from tt where seckey = 1;
> Seq Scan on tt (cost=0.00..168.50 rows=1669 width=12) (actual
> time=0.000..15.000 rows=1784 loops=1)
> Filter: (seckey = 1)
> Total runtime: 31.000 ms

> Now also this simple query uses a "Seq Scan".

Which is exactly what it *should* do, considering that it is selecting
1784 out of 8920 records. Indexscans only win for small selectivities
--- the rule of thumb is that retrieving more than about 1% of the
records should use a seqscan.

regards, tom lane