Ok, why isn't it using *this* index?

I have a table with columns 'country' and 'state'.  I put indexes on both
of them.  I've done the "vacuum analyze" as per the faq.  But when I ask
it to explain, it says it will use the index on 'state' if I do a
    select * from waypoint where state = 'ON';
but it won't use the index on 'country' if I do a
    select * from waypoint where country = 'CANADA';

Some other interesting things are that it uses the index on state even if
I say "where state in ('ON','QC','BC','AB')", and it uses the index on
state but not the one on country if I combine "where state = 'ON' and
country = 'CANADA'".

Here's what it says:
    waypoint=> explain select * from waypoint where state = 'ON';
    NOTICE:  QUERY PLAN:

    Index Scan using waypoint_state on waypoint  (cost=7.17 rows=84
    width=130)

    EXPLAIN
    waypoint=> explain select * from waypoint where country = 'CANADA';
    NOTICE:  QUERY PLAN:

    Seq Scan on waypoint  (cost=455.13 rows=6813 width=130)

    EXPLAIN

Also, can anybody explain why the "rows=" doesn't correspond to anything
logical?  For instance, in the first one it says "rows=84" even though
there are 107 matching records, and 71 different states.


--
Paul Tomblin <ptomblin@xcski.com>, not speaking for anybody
Diplomacy is the ability to let someone else have your way.