Key Range Locks
Lock on B-tree key range is a cheap predicate lock
- Select Dept Where ((Budget > 250)
- lock the key range [221, 352) record
- only useful when query is on an indexed field
- Commonly used with multi-granularity locking
- Insert/delete locks record and intention-write locks range
- MGL tree defines a fixed set of predicates, and thereby avoids predicate satisfiability