I have a table, currently at about 150.000 rows, with a btree index on a
field named 'misscnt'. ~138k of the rows have this fields set as null, ~12k
as 0, ~350 as 1, ~200 as 2 and ~150 as 3 (these are the only values used).
Still, I get the following:
# explain select * from cam where misscnt>=1;
NOTICE: QUERY PLAN:
Seq Scan on cam (cost=0.00..3609.59 rows=46896 width=66)
Why do postgre think it will get over 46k rows from this query? If I try a
VACUUM ANALYZE on the table, I get:
# explain select * from cam where misscnt>=1;
NOTICE: QUERY PLAN:
Seq Scan on cam (cost=0.00..3874.01 rows=50347 width=66)
So now it actually thinks it will get _more_ rows:
# select count(*) from cam where misscnt>=1;count
------- 692
If I use "set enable_seqscan=false;" and try "select * from cam where
misscnt>=1;" the index is used, and the query executes quite a bit faster.
However, shouldn't Postgre be able to do this automatically?
This is using PostgreSQL 7.1.2.
Thanks.
---
Kristian Eide
