Re: Index not used on single select, but used in join.

On Wed, 7 Nov 2001, Tom Lane wrote:

> What does EXPLAIN actually show for you? If you try to force an
> indexscan by doing "SET enable_seqscan TO off", does the EXPLAIN
> result change? Have you VACUUM ANALYZEd the table recently?

After I tested with setting enable_seqscan to off I did a VACUUM ANALYZE.
Turned the variable to on and did another explain. It is back to trying to
do a sequential scan.

drf=# SET enable_seqscan TO on;
SET VARIABLE
drf=# explain select horse from hraces where lower(horse) = 'little irish nut';
NOTICE: QUERY PLAN:

Seq Scan on hraces (cost=0.00..208976.96 rows=75793 width=12)
EXPLAIN

It is a little troublesome that the optimizer is choosing the
sequential scan. This query with lower(horse) is extremely common in
our environment.

We are a Foxpro and Oracle shop and I am jut starting to do tests with
PostgreSQL to see its capability to handle at least part of our operation
in the future.