b* tree index vs no full table scan

[gopi]

I think you are correctly thinking by assuming that full table scans will be faster than Index lookups because of low cardinality. The bottom line is that a certain percentage threshold of retrieved rows is indeed faster in FTS than index -I believe the threshold is (ahmmmmm???...) 20%?

two things:

1. analyze the table(s) with compute statistics and see what the CBO chooses.

2. use the /*+ RULE */ hint and force a FTS then,
use the /*+ RULE */ hint and force an Index scan

see which performs better. In other words:

Bench mark!!!!
Bench mark!!!!
Bench mark!!!!