Parallel build of non-partitioned join hash tables and non-enforced n:1 join hash tables

摘要

A method for building a hash table over a subset of data in a data set includes partitioning a subset of keys and values in the data set into multiple partitions. A hash table is formed with space reserved for each partition based on cumulative counts for a number of keys and values in each partition of the multiple partitions. Each thread selects one or more partitions and inserts keys and values belonging to the selected one or more partitions into the hash table in the reserved space for those partitions. A compact hash table is created that includes a bitmap and a compacted army.