| 摘要 |
A system, method, and computer program product to improve XML query processing efficiency with virtual cursors. Structural joins are a fundamental operation in XML query processing, and substantial work exists on index-based algorithms for executing them. Two well-known index features-path indices and ancestor information-are combined in a novel way to replace at least some of the physical index cursors in a structural join with virtual cursors. The position of a virtual cursor is derived from the path and ancestor information of a physical cursor. Virtual cursors can be easily incorporated into existing structural join algorithms. By eliminating index I/O and the processing cost of handling physical inverted lists, virtual cursors can improve the performance of holistic path queries by an order of magnitude or more.
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