发明授权
- 专利标题: Method for refreshing multicolumn tables in a relational data base using minimal information
- 专利标题(中): 使用最少信息在关系数据库中刷新多列表的方法
-
申请号: US693500申请日: 1985-01-22
-
公开(公告)号: US4631673A公开(公告)日: 1986-12-23
- 发明人: Laura M. Haas , Bruce G. Lindsay
- 申请人: Laura M. Haas , Bruce G. Lindsay
- 申请人地址: NY Armonk
- 专利权人: International Business Machines Corporation
- 当前专利权人: International Business Machines Corporation
- 当前专利权人地址: NY Armonk
- 主分类号: G06F12/00
- IPC分类号: G06F12/00 ; G06F7/22 ; G06F17/30 ; G06F15/20
摘要:
A method for refreshing a relational data base snapshot manifest in the form of remote read-only copies of selected portions of a base table. The method takes advantage of the fact that each tuple of the base table has a unique identifier TID associated therewith from the time the record is inserted until it is deleted. The TID references the physical location of the tuple within its relation. Two system-maintained fields are added to the base table. These are PREVTID and update ID. One system-maintained column is required in the snapshot table, i.e. BASE TID. Lastly, a column in the catalog of the snapshot is also maintained, i.e. SNAPHIGH.When the refresh of the snapshot table is required, a single scan of the base relation, in ascending TID sequence, is performed on the base table. The scan produces a series of messages which contain the incremental changes required to update the snapshot table to the current state of the base relation. Upon receipt of the messages at the snapshot table site, a single skip sequential pass across the snapshot in BASE TID sequence is performed to apply the incremental changes. This refreshes the snapshot table to the required state.
公开/授权文献
信息查询