Method and system for performing logical partial declustering

Abstract

A method and system for performing logical partial declustering in a shared-nothing database environment. The solution defines a partial declustering technique that can be used to dynamically adapt the declustering of base tables or intermediate result sets. The partial declustering technique is defined to limit the number of partitions (P) involved in an operation. The technique is defined to limit the operation to a subset of the system partitioning map (SPM). There are two components: the association between the data values and partitions is altered by restricting the data values to P' partition values where P′ is less than P; and the actual partitions of the SPM selected are then derived based on a seed derived from a dynamic parameter, such as a session number, or a static parameter, such as a table identifier. In the case of intermediate result sets the number of P′ partitions selected is a cost based decision based on the estimated number of rows in the input intermediate result sets. In the case of a base table the number of P′ partitions is selected based on the table DDL. There is no physical partitioning definitions, rather logical partitions are defined based on subsetting the SPM.