International Business Machines Corporation

Compaq Computer Corporation, Inc.

Compaq

Christopher M Farrar

Pedro Celis

Harry Anthony Leslie

Diana L Shak

Curt Lee Cotner

Maryela Evelin Weihrauch

Michael John Skarpelos

Robert Thomas Miller

Jay H Vaishnav

An apparatus, system, and method are disclosed for efficiently supporting generic SQL data manipulation statements. The method includes determining whether an SQL statement includes extended indicator parameters such as DEFAULT and UNASSIGNED indicators. The method further includes delaying an authorization check for an operation for an SQL statement using extended indicators, and bypassing an SQL exception where an otherwise unauthorized operation involves an UNASSIGNED variable. The method further includes bypassing a database operation such as a referential integrity check where a data change would induce the database operation, but the data change involves an UNASSIGNED variable. The method further includes modifying the SQL statement when the SQL statement involves an UNASSIGNED variable in a predicate clause, allowing the SQL statement to properly execute.

Apparatus, system, and method for efficiently supporting generic SQL data manipulation statements

A method and apparatus is disclosed for accurately estimating the cost of a database query, including the total computer resources used and estimated elapsed time for the production of a first row and last row of an operator involved in the query and/or the total resources used and elapsed time for returning the overall response to a database query. The method and apparatus accurately accounts for resources used and elapsed time associated with blocking operators, such as sorts and hash joins, which cannot produce a first row until they have completed their operations.

Database query cost model optimizer

The invention provides a mechanism for using statistics, in connection with various database query cost modeling techniques, to more accurately estimate the number of rows and UECs that will be produced by relational operators and predicates in database systems. The ability to accurately estimate the number of rows and UECs returned by a relational operator and/or a predicate is fundamental to computing the cost of a query execution plan. This, in turn, drives the optimizer's ability to select the query plan best suited for the desired performance goal. According to the present invention, histogram statistics are synthesized bottom up from the leaf nodes to the root node of a query tree. Given input statistics in the form of histograms for each operand of a relational operator or predicate, the present inventive method and apparatus merge the input statistics in a way that it simulates the effects of the run time operator on the actual data, so as to produce a predicted row count and UEC for each histogram interval representative of the data that actually will be produced by each such operator or predicate in the query tree. A database query optimizer may use these statistics to select and implement an optimal query plan.

Histogram synthesis modeler for a database query optimizer

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Los Gatos, CA, United States of America

Christopher M Farrar