The Research On Query Optimization Of Native Xml Database

With the increase of the XML application, native XML database technology is taking the attention of the field of database, and query optimization is still one of important research contents.In this article, we are going to build an XML document query optimization model based on the associated elements,from a new angle,after study the relationship between the XML nodes, which will provide a flexible strategy for rapid navigation and retrieval of XML data.Firstly, in order to build the query optimization model based on the associated elements of the XML document, we define primary key, virtual primary key, bridge key, the be-associated subtree, the be-associated key value, the associated subtree and the associated key value. The associated subtree and associated sub-tree can point directly to each other by index.In addition, this paper shows the hash method to access and obtain the couple of primary key and its corresponding sub-tree.Then it gives the time complex degrees analysis of querying associated elements information based on the the model and its query solution.Secondly, it gives five algorithms, including Designate Key Value Algorithm, Binding TreeTuple Algorithm, Relate TreeTuple Algorithm, Anti-Relate TreeTuple Algorithm and Index Mapping Algorithm, achieving a query associated elements information plan through a combination of these five algorithms.Finally, we test the model and its algorithms on the the XMark test set, and taking query time as the performance index,compare with reference XQuery statements of the XMark benchmark, to verify the feasibility and effectiveness of the associated element-based query optimization model and its algorithms proposed.