Patent ID: 8510280
Filing Date: 2013-08-13
Classification: G06F

Abstract:
1. A method of performing a parallel join operation in a parallel processing system, comprising: distributing a respective set of rows of a first table and a second table involved in a join operation to each of a plurality of processing modules, wherein the join operation comprises a join on a first column of the first table and a second column of the second table; allocating a respective first spool and a respective second spool to each of the plurality of processing modules; hashing at least a portion of the respective set of rows of the first table on the first column and at least a portion of the respective set of rows of the second table on the second column by each of the plurality of processing modules; redistributing, by each of the plurality of processing modules, at least a portion of the rows of the respective distributed set of rows of the first table and the second table distributed thereto based on a hash value of one of the first column and the second column to one of the plurality of processing modules; thereafter, detecting, by a first processing module of the plurality of processing modules, a skewed value of the first column; and transmitting a notification, by the first processing module, to each of the plurality of processing modules of the skewed value of the first column after the detecting by the first processing module.