Research And Implementation Of Cursor And Trigger Mechanism In DBMS

With the coming of the information era, Database Management System (DBMS) has received more and more attention as the kernel of most information systems. Some national academes have made their own DBMS, such as GKD-Base. Compared with commercial DBMS, they have many limitations for lack of some important functions. Many confidential departments still have to construct their application based on the foreign commercial DBMS, which is a hidden trouble in security. It is imperious to improve the existing native DBMS. For this background, this project is brought out to get more ability by adding some function.Firstly, this paper designs the design of GKD-Base PL/SQL engine's structure, and then researches some key technology in implementation. Secondly, the paper analyses and compares some mainstream DBMS and researches the PostgreSQL's kernel source code, and carries out the implementation scheme of the cursor and trigger mechanism. And finally, the cursor and trigger function are implemented on the GKD-Base PL/SQL engine.In the implementation of cursor, GKD-Base's SQL engine serves as an interface for compiling and executing SQL DML, which is the necessary precondition for cursor. Different cursors, such as explicit cursor, implicit cursor, cursor loop, parameterized cursor, cursor variable, are realized. In the implementation of trigger, some succeed experience of other DBMS is incorporated for event detection, condition test, and so on. The algorithms of trigger's compiling, storing and firing were carried out and implemented on GKD-Base. Finally, the implementation of active mechanism with ECA mediator is discussed.GKD-Base PL/SQL engine and cursor and trigger is compatible with ORACLE.