The following structured query provides an example for optimizing statistics.
select score(1) from tab where contains(txt, 'freedom', 1) > 0 and author = 'King' and year > 1960;
Assume the author column is of type VARCHAR2 and the year column is of type NUMBER. Assume that there is a b-tree index on the author column.
Also assume that the structured author predicate is highly selective with respect to the CONTAINS predicate and the year predicate. That is, the structured predicate (author = 'King') returns a much smaller number of rows with respect to the year and CONTAINS predicates individually, say 5 rows returned versus 1000 and 1500 rows respectively.
In this situation, Oracle Text can execute this query more efficiently by first doing a b-tree index range scan on the structured predicate (author = 'King'), followed by a table access by rowid, and then applying the other two predicates to the rows returned from the b-tree table access.