International Business Machines Corporation

Demai Ni

Yao-Ching Stephen Chen

Irene Ching-Hua Liu

Thomas Abel Beavin

Fen-Ling Lin

Mengchu Cai

Jerry Mukai

Li Jun Xia

Yoichi Tsuji

Ying Zeng

Hsiuying Yen Cheng

Guogen Zhang

Qinghua Zou

Techniques are provided that determine that a query includes at least one subquery that may be correlated or decorrelated. An internal representation of the query that represents the subquery in both correlated and decorrelated form is generated, wherein the internal representation includes at least one virtual table.

Cost-based subquery correlation and decorrelation

A method generates hierarchical path index keys for single and multiple indexes with one scan of a document. Each data node of the document is scanned and matches to query nodes are identified. A data node matches a query node if the three conditions hold: if it is not the root step, there is a match for the query node in the previous step of the query; the data node matches the query node of the current step; and the edges of the data and query nodes match. A sub-tree of a data node can be skipped if the data node is not matched and its level is less than the fixed levels of the query. The matched data node is then placed in the match stacks corresponding to the match query nodes. The method uses transitivity properties among matching units to reduce the number of states that need to be tracked and to improve the evaluation of path expressions significantly.

Streaming XPath algorithm for XPath value index key generation

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Davis, CA, United States of America

Demai Ni