Hewlett-Packard Development Company, L.p.

Murali Mallela Krishna

Harumi Kuno

Goetz Graefe

Janet Lynn Wiener

Hansjorg Zeller

Suresh Subbiah

Vijay Sarathy

Lars Fredriksen

Subrata Naskar

Computer-implemented systems and associated operating methods use atomic query maps to identify and evaluate database query plan robustness landmarks. The computer-implemented system comprises logic that evaluates robustness of a selected atomic query by measuring performance of atomic query execution in a predetermined range of runtime conditions that include data characteristics. The logic produces a set of measurements that can be displayed as one or more performance maps and analyzes the measured performance to identify landmarks indicative of database atomic query performance degradation greater than a predetermined amount.

Evaluation of set of representative query performance using robustness mapping

There is provided a computer-implemented method of optimizing a query. An exemplary method comprises receiving a first query configured to generate a result set. The query may comprise an operation for an outer table, a first predicate, and a second predicate. The second predicate may comprise a subquery correlated to the operation. Additionally, the first predicate and the second predicate may be disjunctive. The exemplary method also comprises generating a first query tree representing the first query, and generating a second query tree representing a second query. The second query may be configured to generate the result set, and may not comprise the subquery. The exemplary method additionally comprises generating a query plan based on the second query tree.

System and method for optimizing queries

A method of performing a database join includes receiving a query. The query may specify a join of a first table and a second table. The method further includes determining a new predicate based on a mapping between a first column of the first table and a second column of the second table for a plurality of tuples of the join. Further, the method includes modifying the query such that the query comprises the new predicate.

Performing database joins

One embodiment relates to a computer-implemented method to estimate a cardinality of a database query. Single table cardinalities are determined after application of selection predicates. In addition, pair-wise join selectivities are estimated without assuming independence between selection and join predicates. Said pair-wise join selectivities are multiplied with said single table cardinalities after application of the selection predicates. Another embodiment relates to a computer apparatus including a cardinality estimator. The cardinality estimator includes computer-readable instructions configured to (a) determine single table cardinalities after application of selection predicates from the database query, (b) estimate pair-wise join selectivities without assuming independence between the selection predicates and join predicates of the database query, and (c) multiply said pair-wise join selectivities with said single table cardinalities after application of the selection predicates. Other embodiments, aspects and features are also disclosed.

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Vancouver, WA, United States of America

Murali Mallela Krishna