Research On Sbjects Seraching And Materialized View Technology In Data Warehouse

Warehousing is an emerging technique for retrieval and integration of data from distributed, autonomous, possibly heterogeneous, information sources. Data warehouse is a repository of integrated information drawn form remote data sources, available for queries and analysis. By using the data and information from the data warehouse, we can obtain more benefit. Currently, it has many hotspots of data warehouse, such as building the subjects, selecting the materialized views, maintaining the materialized views, On-Line Analytical Processing, On-Line Analytical Processing and Data Mining and optimizing queries.Firstly, a new arithmetic for searching subject in data warehouse is proposed. It could objectively choose tables, which are fit for the subjects. By comparing with the subjects obtained by requirement analyzing, the new arithmetic is proved right. In addition, it could find out the tables fit for subjects by analyzing unknown database and assist designers to make fact tables.Secondly, a new cost value model is proposed. Based on this model, the arithmetic for selecting the views which should be materialized is brought forward. It could reduce effectively the amount of views by pre-processing. The new model considers query frequency and update frequency. Comparing with inhere arithmetic, the time complexity and maintenance cost is decreased, and the query efficiency of materialized views are improved.Thirdly, dynamic view maintenance technique based on timestamp is proposed, which adopts version-control technique. It preserves the synchronization of the querying and updating views by controlling the timestamp, which effectively solves the conflict of OLAP updating affair andOLAP accessing to database at the same time. Besides, it does not only satisfy the maintenance of views on-line real time, but also improves the freshness of data warehouse and querying efficiency of OLAP.Experimental results show that the algorithms proposed in this paper are more efficient than the current ones, and the anticipated results are realized.