Hewlett-Packard Development Company, L.p.

Hewlett Packard Enterprise Development LP

Renu Varshneya

Awny Kayed Al-Omari

Roger Mitchell

Ramakumar Kosuru

Robert L Wall

There is provided a computer-implemented method of optimizing a query. An exemplary method retrieves a subset of rows from a sample table based on a query for a table associated with the sample table. The query specifies the table. The sample table is generated in a previous optimization of the query. The sample table includes a scrambled, random selection of rows from the table. A cardinality of the table is determined based on the subset. A query plan is generated based on the query and the cardinality.

System and method for optimizing queries

There is provided a computer-implemented method of optimizing a query. An exemplary method comprises receiving a first request from an optimizer that specifies a table, a first predicate and a first sample size, wherein the optimizer is optimizing a relational query language statement that specifies the table and the first predicate. The exemplary method also comprises generating a sample table, comprising a first subset of rows from the table, based on the request. The exemplary method also comprises selecting a second subset of rows from the sample table based on the predicate. The exemplary method additionally comprises sending a count of rows in the second subset to the optimizer.

One embodiment is a method that determines skew to predict costs for query plans for a database query. The method selects a query plan that accounts for the skew to evenly distribute processing load among multiple processors and then executes the query with the selected query plan.

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Cupertino, CA, United States of America

Renu Varshneya