Module result 

Certainty-tagged wrappers around a row-address mask returned by a scalar-index expression evaluation.

These types model the three possible degrees of knowledge an index search can return:

• Exact — the mask is the precise answer; no recheck needed.
• AtMost — the mask is a superset of the true answer; the rows inside the mask must be rechecked against the predicate.
• AtLeast — the mask is a subset of the true answer; the rows outside the mask must be rechecked against the predicate.

The boolean algebra (Not/BitAnd/BitOr) is implemented on both NullableIndexExprResult (the form during evaluation, carrying SQL three-valued logic via NullableRowAddrMask) and IndexExprResult (the form consumed by the read planner, after drop_nulls collapses NULL rows into FALSE).

Enums

IndexExprResult

Result of an index search after NULL rows have been dropped. This is what the read planner consumes.

NullableIndexExprResult

Result of an index search before NULL rows are dropped. Carries three-valued-logic information via NullableRowAddrMask.