Abstract: A method, computer-implemented system, and computer program product for creating indexes over XML data managed by a database system are provided. The method, computer-implemented system, and computer program product provide for receiving a workload for the XML data, the workload including one or more database statements, utilizing an optimizer of the database system to enumerate a set of one or more path expressions by creating a virtual universal index based on the workload received and matching a path expression to the virtual universal index, and recommending one or more path expressions from the set of one or more candidate path expressions to create the indexes over the XML data.

Abstract: A system of redistributing partitions across servers having multiple partitions that each process transactions. Where the transactions are related to one another and the transactions are able to access one or a set of partitions simultaneously.

Abstract: A method, computer-implemented system, and computer program product for creating indexes over XML data managed by a database system are provided. The method, computer-implemented system, and computer program product provide for receiving a workload for the XML data, the workload including one or more database statements, utilizing an optimizer of the database system to enumerate a set of one or more path expressions by creating a virtual universal index based on the workload received and matching a path expression to the virtual universal index, and recommending one or more path expressions from the set of one or more candidate path expressions to create the indexes over the XML data.

Abstract: A method, system, and computer program product for selecting indexes to be created over XML data are provided. The method, system, and computer program product provide for receiving a workload for the XML data, the workload including one or more database statements, and utilizing an optimizer to recommend a set of one or more path expressions based on the workload received, wherein the set of one or more path expressions is to be used to create one or more indexes over the XML data.

Abstract: A method, system, and computer program product for selecting indexes to be created over XML data are provided. The method, system, and computer program product provide for receiving a workload for the XML data, the workload including one or more database statements, and utilizing an optimizer to recommend a set of one or more path expressions based on the workload received, wherein the set of one or more path expressions is to be used to create one or more indexes over the XML data.

Abstract: Database system query optimizers use several techniques such as histograms and sampling to estimate the result sizes of operators and sub-plans (operator trees) and the number of distinct values in their outputs. Instead of estimates, the invention uses the exact actual values of the result sizes and the number of distinct values in the outputs of sub-plans encountered by the optimizer. This is achieved by optimizing the query in phases. In each phase, newly encountered sub-plans are recorded for which result size and/or distinct value estimates are required. These sub-plans are executed at the end of the phase to determine their actual result sizes and the actual number of distinct values in their outputs. In subsequent phases, the optimizer uses these actual values when it encounters the same sub-plan again.

Abstract: Building histograms by using feedback information about the execution of query workload rather than by examining the data helps reduce the cost of building and maintaining histograms. A method of maintaining self-tuning histograms updates histograms based on feedback about the execution of a user query. A histogram may be initialized using an assumption of uniform distribution of data or by combining existing histograms. A histogram tuner accesses and estimated result in response to a user query generated by using the histogram. The histogram tuner calculates an estimation error based on the result of the user query and the estimated result. The frequencies of histogram buckets are refined based on the estimation error. The bucket bounds of the histogram are restructured based on the refined frequencies. The method may be performed on-line after a user query or off-line by accessing a workload log.