Guy M. Lohman

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Virtually all proposals for querying XML include a class of query we term “containment queries”. It is also clear that in the foreseeable future, a substantial amount of XML data will be stored in relational database systems. This raises the question of how to support these containment queries. The inverted list technology that underlies much of(More)
Virtually every commercial query optimizer chooses the best plan for a query using a cost model that relies heavily on accurate cardinality estimation. Cardinality estimation errors can occur due to the use of inaccurate statistics, invalid assumptions about attribute independence, parameter markers, and so on. Cardinality estimation errors may cause the(More)
DB2 with BLU Acceleration deeply integrates innovative new techniques for defining and processing column-organized tables that speed read-mostly Business Intelligence queries by 10 to 50 times and improve compression by 3 to 10 times, compared to traditional row-organized tables, without the complexity of defining indexes or materialized views on those(More)
The DB2 Design Advisor in IBM® DB2® Universal DatabaseTM (DB2 UDB) Version 8.2 for Linux®, UNIX® and Windows® is a tool that, for a given workload, automatically recommends physical design features that are any subset of indexes, materialized query tables (also called materialized views), shared-nothing database partitionings, and multidimensional(More)
Since relational database management systems typically support only diadic join operators as primitive operations, a query optimizer must choose the “best” scquence of two-way joins to achieve the N-way join of tables requested by a query. The computational complexity of this optimization process is dominated by the number of such possible sequences that(More)
This paper introduces the concept of letting an RDBMS Optimizer optimize its own environment. In our project, we have used the DB2 Optimizer to tackle the index selection problem, a variation of the knapack problem. This paper will discuss our implementation of index recommendation, the user interface, and provide measurements on the quality of the(More)
This paper describes the overall architecture and design aspects of a hybrid relational and XML database system called System RX. We believe that such a system is fundamental in the evolution of enterprise data management solutions: XML and relational data will co-exist and complement each other in enterprise solutions. Furthermore, a successful XML(More)
Few database query optimizer models have been validated against actual performance. This paper extends an earlier optimizer validation and performance evaluation of R’ to di.rfribu& queries, i.e. single SQL statements having tables at multiple sites. Actual R* message, I/O, and CPU resources consumed and the corresponding costs estimated by the optimizer(More)
Physical database design is important for query performance in a shared-nothing parallel database system, in which data is horizontally partitioned among multiple independent nodes. We seek to automate the process of data partitioning. Given a workload of SQL statements, we seek to determine automatically how to partition the base data across multiple nodes(More)