ParGRES: a middleware for executing OLAP queries in parallel

ParGRES is a middleware aimed to efficiently process heavy weight queries, typical of OLAP, on top of a database cluster. ParGRES achieves query processing speed-up through intra- and inter-query parallelism in a PC cluster environment with database replication and virtual partitioning. It accelerates both individual queries and system throughput. Our experimental results show that ParGRES yields super-linear or near-linear speed-up. ParGRES middleware keeps application and database autonomy. As a result, it offers a non-intrusive migration solution from sequential to a parallel environment. Currently, ParGRES uses PostgreSQL, but it is not DBMS dependent, and has a Web administration tool. The main features of ParGRES are: automatic parsing of SQL queries to allow for intra-query parallel execution; query processing with inter- and intra-query parallelism; virtual dynamic partition definition; result composition; update processing; and dynamic load balancing. The main contribution of ParGRES is to combine inter and intra-query parallelism with dynamic load balancing for virtual partitions, all within an open source cost-effective solution.