why isn't index used?

Hi all,

Just spent last day scratching my head over why the following simple
query wasn't using the index...

select b,c from testing where a=99999;

The table was...

CREATE TABLE testing
(
a int8 NOT NULL,
b text NOT NULL,
c text NOT NULL
);

I generated 100,000 rows using a small perl program.

print "copy testing from stdin;\n";
for (1..100000) {
print "$_ one two\n";
}
print "\\.\n";

and created an index using...

create index testing_a_key on testing (a);

and then ran Analyze command.

analyze;

Then tried the following...

nooper=# explain select b,c from testing where a=99999;
NOTICE: QUERY PLAN:
Seq Scan on testing (cost=0.00..1987.20 rows=1 width=14)
EXPLAIN

nooper=# explain select b,c from testing where a=99999::int8;
NOTICE: QUERY PLAN:
Index Scan using testing_a_key on testing (cost=0.00..3.01 rows=1
width=14)
EXPLAIN

In the first case you'll note that I didn't explicitly cast to bigint
and the index is not used even if I turn off enable_seqscan. Only when I
explicitly cast to bigint does it get used. This seems a little brain
dead to me, no? Is this the expected behaviour?

I'm using 7.2.1 currently. Maybe its different in upcoming 7.3?

Tom.
--
Thomas O'Dowd. - Nooping - http://nooper.com
tom(at)nooper(dot)com - Testing - http://nooper.co.jp/labs