Maintains the coherence between the local index table and the global index table in multilayer index structure the manner

摘要

A multi-tiered indexing method is disclosed for a partitioned table in a parallel or distributed database system. A Local Index is created and maintained for each partition of the table and a Coarse Global Index is created and maintained. The Coarse Global Index identifies the indexed partition(s) by partition identifiers (PIDs) and associates the individual Index Key Values with their target partitions so that an access request with a highly partition-selective search predicate on the Index Key can be quickly and easily directed to the target partition(s) for processing. An index maintenance locking protocol is also disclosed which handles the insertion and deletion of index entries and assures the consistency between the Local Index entries and the Coarse Global Index entries during concurrent index accesses by different transactions. The locking protocol minimizes locking only to those cases involving an inserted or deleted key and to the key following and possibly the key preceding the inserted or deleted key to allow high concurrency between simultaneous Readers, Inserters, and Deleters. This method enhances the efficiency of complex query evaluation and index maintenance and attains a high throughput for transaction processing.