International Business Machines Corporation

Andrei Fedorovich Lurie

Terence Patrick Purcell

Thomas Abel Beavin

Shuanglin Guo

Brian L Baggett

Martina Simova

Christopher John Crone

Oliver Draese

Patrick Dooling Bossman

Shengxi Suo

Ying Zeng

Jonathan Sloan

You-Chin Gene Fuh

Fen-Ling Lin

Li Jun Xia

John Joseph Campbell

Johannes Schuetzner

Margaret Ann Bernal

Dirk Nakott

Yoichi Tsuji

Jason Alexander Cu

Daya Vivek

Saghi Amirsoleymani

Provided are techniques for efficient subquery predicate generation to reduce processing in a multi-table join. It is determined that a query is to be rewritten, wherein the query includes a predicate for a first column of a first table and a second column of a second table. The query is rewritten with generated subquery predicates for the first table that are to be applied to the second table and with generated subquery predicates for the second table that are to be applied to the first table. Minimum and maximum ranges for columns of the generated subquery predicates at a cursor open are determined. The minimum and maximum ranges are merged to determine inclusive ranges that exist in the first table and the second table. The generated subquery predicates are rewritten as derived local subquery predicates with the inclusive ranges. The query with the derived local subquery predicates is executed.

Subquery predicate generation to reduce processing in a multi-table join

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

A method, a computer program product and a system are provided. A case expression is analyzed for redundant expressions, patterns equivalent to a built-in function, and specific functions to form a simplified expression, wherein the case expression is written in a language supported by a database management system. The simplified expression is optimized based on a cost benefit evaluation of no optimization, native code generation, hashing inputs, and a results caching algorithm to form an execution plan. The execution plan is utilized in the database management system for the case expression.

Case statement optimization

Provided are techniques for progressive optimization for implicit CAST predicates. In response to receiving a query with an original predicate comparing a character value of a character data type to a literal value of a numeric data type, a number of iterations is set to a length of the character data type. For each of the number of iterations, prefix predicates are generated based on that iteration and processed to identify a qualified index key in an index. Once the iterations are completed, the character value and the literal value are normalized. The original predicate with the normalized character value and the normalized literal value is applied starting at the qualified index key identified in a last iteration to generate a result set for the query. The result set is returned.

Progressive optimization for implicit cast predicates

Disclosed aspects relate to index maintenance management of a relational database management system having a set of indexes. A subset of the set of indexes, which is indicated as a non-critical index subset, is detected with respect to the set of indexes. Related to maintenance of the subset of the set of indexes, a determination is made to perform an index maintenance impact action. Corresponding to the subset of the set of indexes, the index maintenance impact action is performed.

Index maintenance management of a relational 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

In an index-only multi-index access in a database, when a query to be executed requires multiple indexes, a query optimizer determines whether columns are needed for a query result, subquery, or inner join result. If not, then the query result is resolved using qualified record identifiers (RIDs) from the multiple indexes without accessing the data pages. When the columns are needed and can be resolved using input values of the query, then the query result is resolved using the qualified RIDs from the multiple indexes and substituting column values with the input values of the query. When the columns are needed and cannot be resolved using the input values of the query, the query optimizer may store one or more index keys with its corresponding qualified RIDs from the multiple indexes and may resolve the query result using the stored index keys without accessing the data pages of the database.

Index-only multi-index access

Dynamically switching between a plurality of execution paths to execute a function, such as a user-defined function. The plurality of execution paths include an execution path that uses caching and another execution path that uses inlining. A user-defined function is executed at least once using a first execution path. Then, for a later execution of the function, the execution path is automatically switched to a second execution path.

Dynamically switching between execution paths for user-defined functions

Embodiments of techniques related to optimizing and processing queries are disclosed. In one embodiment, a query to access data of one or more databases is received, and a hybrid access path for accessing the data is generated. Generating the hybrid access path may include determining a plurality of candidate access paths and respective path cost values and selecting, based on the respective path cost values, two or more candidate access paths from the plurality of candidate access paths. Generating the hybrid access path may include generating, based on the two or more candidate access paths, the hybrid access path, the hybrid access path including at least one decision point and a set of options. The at least one decision point of the hybrid access path may indicate a difference between two or more candidate sequences of operations of candidate access paths from the two or more candidate access paths.

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San Jose, CA, United States of America

Andrei Fedorovich Lurie