In the LT/ST-J1 class index join, a combination of the join columns of the small tables comprises an index of the large table.
Reasonable Indexed Joins, LT/ST-J1a
This subclass consists of those LT/ST-J1 joins in which the cardinality of the Cartesian product of the small tables is small relative to the cardinality of the large table.
The magnitude of this cardinality difference depends on factors such as the following, and therefore cannot be defined rigorously:
- Types of indexes defined
- Conditions used by the old join plan
- Conditions used by the new join plan
- Size of the columns retrieved from the small tables
Unreasonable Indexed Joins, LT/ST-J1b
This subclass consists of all LT/ST-J1 joins that are not of subclass LT/ST-J1a (Reasonable Indexed Joins).