Database management system, method and program for supporting the

Abstract

The system, method, and program of this invention avoids potential write/write conflicts and read/write conflicts when a subcomponent of a composite object (e.g., an ADT) is mutated. The embodiments of this invention define a copy semantic for the mutation function. In one embodiment, a copy function is inserted prior to any mutation function. In a another embodiment, a global compile-time analysis is performed to determine if a write/write or read/write conflict exists; and to eliminate redundant copy constructors if a conflict does exist. In a preferred embodiment, only a local analysis is performed during the parsing phase, thereby avoiding a global compile-time analysis. A mutation safe flag is associated with each parse tree node. A read target leaf parse tree node is set to false while non-leaf parse tree nodes (functions) derive their value from an incoming node, except that constructors and copy constructor functions are always true. Whether or not a copy is made of the composite object (i.e., whether or not a copy constructor is inserted) prior to a mutation is determined according to the setting of the mutation safe flags and according to the following. If a mutation safe flag for a mutation function is false, a copy constructor is inserted for the mutated composite object and the mutation safe flag is set to true. In addition, for update and trigger statements, the mutation safe flag for a mutated target is defaulted to true. Furthermore, related update entries are grouped together and a copy is generated for the common target. The generated copy is used as the common target for all of the mutations caused by the update entries grouped together in order to accumulate all of the desired mutations in a same copy of the composite object.