视图的分布式数据共享机制与更新技术

在分布式空间数据库系统中,空间数据共享一般采用基于数据快照的共享机制来实现。该技术方法的基础是在本地数据库中保存远程空间数据的副本,因而将造成大量的数据存储冗余,并使得数据的一致性维护困难。本文提出一种基于视图的分布式数据共享方法,通过建立远程空间数据表的本地视图,再为该视图建立由更新操作触发的行级替代触发器,并在该触发器内编码,以解决远程空间表的本地视图不可更新问题;并通过所扩展的视图更新和查询功能,实现分布式环境下远程空间数据的本地共享。基于Oracle 9i的应用实例验证了本文所提出的共享机制,取得了令人满意的效果。

A View-based Mechanism for Updating and Sharing Distributed Spatial Database

In a distributed spatial database system, spatial data is currently shared with a snapshot-based mechanism. This method is charcateristic of maintaining copies of remote spatial datasets in local databases, and thus inevitably results in great data srorage redundancy and difficulty in preserving data consistency. In this paper, however, a view-based sharing method is put forward to solve this problem. Firstly, a local view is created corresponding to a remote spatial table, then an 'instead-of trigger for modifying each row is set up on the view to enable it modifiable. So local access to remote spatial data in a distributed database environment can be implemented with the extended view-modifying functions and view-selecting functions directly from Database Management System (DBMS). A case based on an Oracle 9i database management system validates the feasibility of this view-based data sharing mechanism, with a satisfactory result.