International Business Machines Corporation

Shuanglin Guo

Terence Patrick Purcell

Patrick Dooling Bossman

Thomas Abel Beavin

Brian L Baggett

Andrei Fedorovich Lurie

Yoichi Tsuji

You-Chin Gene Fuh

Oliver Draese

Shengxi Suo

Chan-Hua Liu

Jason L Alpers

Martina Simova

Michael A Chang

Hsiuying Yen Cheng

Patrick Michael Malone

Ou Jin

Xun Li

Brian Tran

Changjiu Xian

Xiazhen Wang

A method, system and computer program product are provided. A first index scan of records of a database table is performed. A first index used by the first index scan is specified in a DBMS query statement as being ordered by one or more field values of one or more fields of the first index. A second scan of the database table is performed to determine whether each respective record of the second scan is qualified based on one or more fields of the each respective record of the second scan and a predicate. A lookup data structure is built indicating whether each of the respective records of the second scan is qualified. The lookup data structure is used to determine whether a record of the first index scan is qualified when the lookup data structure becomes available.

Helper scan in a database management system

An access plan including multiple indexes is selected for accessing data of a database system. A filtering status of each index within the selected access plan is determined based on information available at execution of the selected access plan. The order of the indexes within the selected access plan is modified based on the filtering status of the indexes, and the selected access plan is executed with the modified order of the indexes. The execution of the selected access plan is interrupted in response to accessing a threshold amount of data and the filtering of the indexes of the selected access plan is estimated. A processing order for the indexes is determined based on the estimated filtering. The execution of the selected access plan resumes based on the determined processing order.

Adaptive multi-index access plan for database queries

Provided are techniques for a Data-Partitioned Secondary Index (DPSI) partition level join. While using a Data-Partitioned Secondary Index (DPSI) to perform a join of an outer table and an inner table, a different task from multiple tasks is assigned to each partition of the inner table. With each task, a join is performed of the outer table and the assigned partition of the inner table using the DPSI to generate results. The results from each different task are merged.

Data-partitioned secondary index (DPSI) partition level join

A technique for factoring uncertainty into cost-based query optimization includes: determining the degree of uncertainty involved in the cost estimates for the query, determining the degree of sensitivity the query has to that uncertainty, and determining if there is an access path that performs well across the range of possible conditions that could occur at execution time, reducing the risk of performance spikes and performance volatility. If such an access path exists, select that access path; if not, perform parametric query optimization or query re-optimization.

Technique for factoring uncertainty into cost-based query optimization

A method and system are presented for quantifying a data page repetition pattern for a database index in a database management system. In one embodiment, the method includes identifying a database index to provide a basis for collecting a data page repetition statistic, the database index having a database index key. The method may also include collecting the data page repetition statistic based on the database index key, wherein the data page repetition statistic quantifies a data page repetition pattern associated with database queries that reference sequential entries of the database index. The method may further include optimizing a data page access process based on the data page repetition statistic. In a further embodiment, the method may utilize both cluster ratio and data page repetition statistics to evaluate data page I/O and CPU cost.

Method and system for quantifying a data page repetition pattern for a database index in a database management system

A method of, a computer program product for and a computer system for managing statistics in a database management system are provided. A value of a volatility of a statistic is determined. A value of a staleness of the statistic is determined using the value of the volatility. A statistics collection task is generated in response to, at least in part, the value of the staleness exceeding a value of a staleness threshold. The statistics collection task is executed to collect an additional value of the statistic. The additional value of the statistic is stored.

Management of database statistics

In various embodiments, a method, apparatus, and article of manufacture collect statistics in a database management system. A workload comprising a plurality of database queries is received. Query statistics for the database queries are identified. The query statistics for the database queries are consolidated to provide consolidated statistics. One or more statistics collection requests are generated based on the consolidated statistics.

Query workload statistics collection in a database management system

A method, apparatus, and article of manufacture for improving the performance of evaluating predicates with non-matching operands by aggressively casting the input value to the data type of the target column before the data of the target column is accessed.

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Cupertino, CA, United States of America

Shuanglin Guo