Two emerging hardware trends will dominate the database system technology in the near future: increasing main memory capacities of several TB per server and massively parallel multi-core processing. Many algorithmic and control techniques in current database technology were devised for diskbased systems where I/O dominated the performance. In this work we take a new look at the well-known sort-merge join which, so far, has not been in the focus of research in scalable massively parallel multi-core data processing as it was deemed inferior to hash joins. We devise a suite of new massively parallel sort-merge (MPSM) join algorithms that are based on partial partition-based sorting. Contrary to classical sort-merge joins, our MPSM algorithms do not rely on a hard to parallelize final merge step to create one complete sort order. Rather they work on the independently created runs in parallel. This way our MPSM algorithms are NUMA-affine as all the sorting is carried out on local memory partitions. An extensive experimental evaluation on a modern 32-core machine with one TB of main memory proves the competitive performance of MPSM on large main memory databases with billions of objects. It scales (almost) linearly in the number of employed cores and clearly outperforms competing hash join proposals -in particular it outperforms the "cutting-edge" Vectorwise parallel query engine by a factor of four.

Abstract. Driven by the two main hardware trends increasing main memory and massively parallel multi-core processing in the past few years, there has been much research eort in parallelizing well-known join algorithms. However, the non-uniform memory access (NUMA) of these architectures to main memory has only gained limited attention in the design of these algorithms. We study recent proposals of main memory hash join implementations and identify their major performance problems on NUMA architectures. We then develop a NUMA-aware hash join for massively parallel environments, and show how the specic implementation details aect the performance on a NUMA system. Our experimental evaluation shows that a carefully engineered hash join implementation outperforms previous high performance hash joins by a factor of more than two, resulting in an unprecedented throughput of 3/4 billion join argument tuples per second.

Complex business processes are usually realized by specifying the integration and interaction of smaller modular software components. For example, hitherto monolithic enterprise resource planning systems (ERP) are decomposed into Web services which are then again orchestrated in terms of Web service workflows, bringing about higher levels of flexibility and adaptability. In general, such services constitute autonomous software components with their own dedicated security requirements. In this paper we present our approach for consolidating the access control of (Web service) workflows. The proposed security engineering method allows, first, to determine for whom workflows are executable from a privileges point of view, second, to assess compliance with the principle of least privilege, and, third, helps to reduce policy enforcement costs.

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