Research And Implementation Of Key Technologies In PL/SQL Engine

X-BASE is a native Security Database Management System.Along with the development of database technology, X-BASE DBMS becomes shortage of some popular mechanisms, such as PL/SQL, key/foreign key, triggers and so on. X-BASE DBMS needs implement PL/SQL engine to meet these demandings.Based on introduction of the infrastructure of PL/SQL engine, more detail structure of the compiling and execution module is discussed. For the internal representaion of the compiled language component of PL/SQL, a concise and compact form of code is designed. The symbol table is implemented by the stack and array,it is of high efficiency to search a given variable names or tokens.The exception mechanism of PL/SQL is analyzed and designed. It contains exception model and exception handler. There are two kinds of exception in PL/SQL, the built-in exception and the user-defined exception. The exception's definition, raise, catch and handling are all discussed in respect of the two kinds.The memory is divided into many kinds of memory pool which possesses different existent. Memory's management contains allocate and free and so on. It needn't release memory block one by one, so which makes all memory blocks is easy to free.We according to ECA model to implement X-BASE DBMS trigger. The mid-code is saved in data dictionary after parsing trigger's code. It is interpreted which is fetched from data dictionary in interpreter. Trigger's implementations contain definition, executing, dead lock and so on.ALL the techniques discussed above have been implemented in X-BASE PL/SQL engine.The engine can steady run now. X-BASE PL/SQL is robust and compatible based on many testing programs.