The Research And Application Of Increasing Pre-fetching In Persistent Framework

In recent years, the object-oriented method has become the mainstream method in the large-scale application development environment. And the relational database has also become the mainstream data-storage system. In the software development, the data appears to an object, but in the relational database its performance as the relational data, so the data in the different areas appears different forms, and in the application system development, the problem that does not match each other must be solved, and the thought of Object Relationship Mapping (Object Relational Mapping, ORM) arises at the historic moment. At present there are many lasting frames based on ORM, Hibernate is the quite popular one, although it is very perfect, there are some insufficiencies.The complex objects mapping and the connection management have the tremendous influence to the lasting frames in system performance. The number of interactive operation increases between Client and Database, it will get the poor performance. The pre-fetching technique can reduce the number of interactive times between Client and Database. According to the relations of the child objects in complex objects, object pre-fetching can store the data in the memory that will be possibly visited in the future, it is convenient for interaction, and it also enhance system's performance.At present, the object pre-fetching technique is effective only in certain circumstances, it is not widely used. For this problem, we propose two incremental pre-fetching techniques:the incremental pre-fetching technique based on control flow chart and the incremental pre-fetching techniques based on the log information. The former technique acts the branch of programming as a key point, each time it will pre-fetch all the objects between the two key points. In the latter method it firstly analyses the running log information and then achieves the object pre-fetching according to the object of the execution path. Both incremental pre-fetching technique can improve the object pre-fetch hit rate and improve query performance.This article introduces the background of ORM framework, its basic ideas and principles, it studies on the relational model, object model, the theoretical thought of persistence and the current popular ORM framework, it also analyses the advantages and disadvantages of ORM framework. In order to solve the problem based on the log information and the program control flow chart of the complex object operation in the persistence framework, this article presents two incremental pre-fetching techniques, it studies on the both two algorithms and implements the incremental pre-fetching techniques based on the log information in persistence framework. In the last, they are used to the Integrated Cabling System; it is proved that the incremental pre-fetching techniques based on the log information can improve the pre-fetch hit rate and high system performance.