In this paper we present HATCH, a novel hash join engine. We follow a new design point which enables us to effectively cache the hash table entries in fast BRAM resources, meanwhile supporting collision resolution in hardware. HATCH enables us to have the best of two worlds: (i) to use the full capacity of the DDR memory to store complete hash tables, and (ii) by employing a cache, to exploit the high access speed of BRAMs. We demonstrate the usefulness of our approach by running hash join operations from 5 TPCH benchmark queries and report speedups up to 2.8x over a pipeline-optimized baseline.

The research leading to these results has received funding from the European Unions Seventh Framework Programme (FP7/2007-2013), for Advanced Analytics for Extremely Large European Databases (AXLE) project under grant agreement number 318633, and from the Ministry of Economy and Competitiveness of Spain under contract number TIN2012-34557.