International Business Machines Corporation

Irene Ching-Hua Liu

Yao-Ching Stephen Chen

Guogen Zhang

Demai Ni

Thomas Abel Beavin

Fen-Ling Lin

Mengchu Cai

Ruiping Li

Jerry Mukai

Li Jun Xia

Lee-Chin Hsu Liu

Yoichi Tsuji

Ying Zeng

Hsiuying Yen Cheng

Yun Yu Wang

Curt Lee Cotner

Gerald George Kiernan

Walid Rjaibi

Timothy Jon Vincent

Brian Thinh-Vinh Tran

Claire Willey McFeely

Qinghua Zou

Stephen Yao Ching Chen

Ding-Wei Chieh

Hsuiying Yen Cheng

Access to a data element stored within a database object is controlled. A request is received from a user to perform an operation in relation to the database object, the operation including retrieval of information from the data element of the database object. Prior to retrieving information from the data element, a determination is made whether at least a portion of the information from the data element is subject to masking in accordance with an access policy. In response to determining that information from the data element is subject to masking, the request is modified to require that information from the data element be retrieved in a masked condition.

Masking sensitive data of table columns retrieved from a database

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

A method and system for efficiently identifying materialized view candidates for queries filters materialized views using certain criteria, using the materialized view signatures. This filtering rejects some of the unqualified materialized views prior to the performance of the query rewrite matching algorithm, resulting in a group of materialized view candidates. The query rewrite matching algorithm is then performed on the materialized view candidates. By first filtering the materialized views based on their signatures, the number of materialized views on which the query rewrite matching algorithm is performed is significantly reduced, improving performance.

Materialized view signature and efficient identification of materialized view candidates for queries

A heuristic approach is used to order materialized view (MW) candidates in a list based on descending order of their reduction power. A query (e.g., SQL query) is then matched with the MVs in the list order, wherein searching is stopped when matching has been found. The query is matched with materialized views in the ordered list by identifying a materialized view candidate as follows: identifying an MV that is not locked by a REFRESH process; identifying a matching MV that does not require a regroup; identifying a matching MV that does not require a rejoin; identifying a matching MV that does not require a residual join; or identifying an MV with largest reduction power from the list of candidates.

Efficient heuristic approach in selection of materialized views when there are multiple matchings to an SQL query

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San Jose, CA, United States of America

Irene Ching-Hua Liu