International Business Machines Corporation

Curtis Neal Boger

Robert J Bestgen

John David Dietel

Randy Lynn Egan

Robert Victor Downer

Daniel Beuch

Shantan Kethireddy

Mark John Anderson

Michael D Pfeifer

Michael Steven Faunce

Scott Forstie

Thomas Owen McKinley

James Michael Flanagan

John Francis Edwards

A database query optimizer includes an access plan storage mechanism that stores execution detail corresponding to a query statement in an access plan cache. By storing execution detail in the access plan cache along with the query statement, the execution detail is available when needed to debug database problems, even after a problem occurs. The execution detail stored in the access plan cache may be mined and analyzed after-the-fact, producing a very powerful tool for debugging database problems. Snapshots of the execution detail may also be created by a user. In addition, the user may setup autonomic snapshots and comparisons so that a user may be alerted from a degradation in database performance between two snapshots.

Database execution detail repository

Optimizers must work with numeric data from a variety of sources including column statistics, estimated filter factors, record counts estimated costs and the like. Embodiments provided herein define and represent any such numeric measurements as a Vector of N dimensions, where n is a number of aspects of measurements that a particular optimizer is configured to consider. A particular embodiment provides a 4-dimensional vector where the dimensions represent magnitude, confidence, variance interval, and penalty. Examples of measurements considered by the optimizer, and which may be represented as a vector, include cost, estimated selectivity of a predicate, estimated number of records returned from part or all of a query, estimated record fanout when joining one file to another, etc.

Representation for data used in query optimization

A metadata manager is used in a database management system to collect and maintain metadata associated with a database. Multiple optimizer instances are permitted to access the metadata maintained by the metadata manager, often eliminating the need for individual optimizer instances to retrieve and process metadata directly from the database. As such, the overhead associated with operations such as collecting, refining, retrieving and/or maintaining of metadata can be off-loaded from the optimizer instances, often accelerating individual cost estimation calculations by optimizer instances, facilitating reuse of metadata calculations and refinements, and improving metadata consistency between multiple related cost estimates.

Metadata manager for database query optimizer

A database query optimizer constructs a graph comprising nodes, relations, and expressions. The query optimizer then constructs execution plans for sub-parts of the graph. The combination of execution plans make up the overall execution plan for the query. The execution plan information is appended to the graph itself, allowing changing an execution plan in one portion of the graph without necessarily changing execution plans in other portions of the graph. By representing a query using the graph of the preferred embodiments that includes execution plan information, the query optimizer is able to evaluate the execution plans of different options quickly and efficiently, thereby enhancing the performance of the query optimizer.

Database query optimization apparatus and method that represents queries as graphs

An apparatus, program product and method utilize a query optimizer that relies upon a plurality of dynamically-dispatchable active strategy entities to generate an optimized execution plan for a database query. The plurality of active strategy entities form a optimizer framework from which the knowledge available to the optimizer, and the intelligence utilized by the optimizer in generating execution plans, may be represented in a structured, flexible, extensible and easily-modifiable manner.

Database query optimizer framework with dynamic strategy dispatch

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Oronoco, MN, United States of America

Curtis Neal Boger