Teradata Us, Inc.

Teradata Corporation

Pekka Kostamaa

Bhashyam Ramesh

Yu Xu

Mark Sirek

A system, method, and computer-readable medium that facilitate management of data skew during a parallel join operation are provided. Portions of tables involved in the join operation are distributed among a plurality of processing modules, and each of the processing modules is provided with a list of skewed values of a join column of a larger table involved in the join operation. Each of the processing modules scans the rows of the tables distributed to the processing modules and compares values of the join columns of both tables with the list of skewed values. Rows of the larger table having non-skewed values in the join column are redistributed, and rows of the larger table having skewed values in the join column are maintained locally at the processing modules. Rows of the smaller table that have non-skewed values in the join column are redistributed, and rows of the smaller table that have skewed values in the join column are duplicated among the processing modules.

System, method, and computer-readable medium for partial redistribution, partial duplication of rows of parallel join operation on skewed data

A system, method, and computer-readable medium for dynamic detection and management of data skew in parallel join operations are provided. Receipt of an excessive number of redistributed rows by a processing module is detected thereby identifying the processing module as a hot processing module. Other processing modules then terminate redistribution of rows to the hot processing module and maintain rows of a skewed table of the join operation that would be redistributed to the hot processing module in a local spool. Rows of a smaller table that would be redistributed to the hot processing module are duplicated to each processing module involved in the join operation. Rows of tables that are to be redistributed by a processing module to any processing module excluding the hot processing module are redistributed accordingly and maintained locally by the processing module. The join operation is completed by merging results of local join data sets of each processing module.

System, method, and computer-readable medium for dynamic detection and management of data skew in parallel join operations

There is provided a parallel database system. Systemincludes a storage devicefor maintaining a plurality of rows. Systemalso includes a plurality of access modulesfor accessing in parallel a respectively assigned one or more of rows. An interfacereceives dataindicative of a tabledefined by a selectionof rows. A processoris responsive to datafor selectively designating tableto be a single-module table. In this single module table, selectionis collectively assigned to an owning one of modules, indicated by reference numeral

Database system

A method, computer system, and database system for automating a business rule in a database are disclosed. One or more database triggers associated with a business rule state machine are enabled and the business rule state machine is initialized.

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Santa Monica, CA, United States of America

Pekka Kostamaa