Abstract: Provided are a method, system, an program for tuning a database query. Provided are a base access plan to implement the database query and statistics including information on a layout of the database against which the query will be executed. The statistics are processed to determine performance problems with the base access plan as part of a first analysis of the base access plan and the determined performance problems are processed as part of a second analysis to provide an analysis of the determined performance problems and processing cost of the base access plan. Recommendations are generated to tune the base access plan to improve performance.

Abstract: Embodiments of the present invention provide a “look-ahead” form prefetch. Look-ahead prefetch may utilize a look-ahead queue to prefetch multiple pages asynchronously. The look-ahead queue may hold a plurality of search keys that are related to a transaction. When accessing a table, an index manager may retrieve the table's index and scan the index based on the search keys from the look-ahead queue to find the RIDs in the table that match the search keys. The index manager may then accumulate these RIDs into a prefetch list. A prefetch manager may read the prefetch list, determine locations for the pages of the table that contain the records identified by the RIDs, and dispatch prefetch tasks to the appropriate storage device for these pages.

Abstract: A method, apparatus, and article of manufacture for optimizing a query in a computer system, wherein the query is performed by the computer system to retrieve data from a database stored on the computer system. The optimization comprises determining an optimal access plan for a first-N-rows query by evaluating a cost of fetching N rows, relative to a total number of rows R in a final results set. Specifically, for a pipelined access plan, this comprises calculating how many rows need to be fetched from each table in the pipelined plan in order to obtain the first N rows from the final results set.

Abstract: Various embodiments of a method, apparatus and article of manufacture of managing statistics in a database management system are provided. A volatility of at least one of statistic is determined. One or more statistics collection tasks are generated based on, at least in part, the volatility.

Abstract: Provided are a method, system, and program for selecting a join order for tables subject to a join operation. An estimation is made of a join cost to perform joins on permutations of at least two of the tables, wherein each join permutation indicates an order of joining the tables. A determination is made as to whether sufficient computational resources are available to perform a join cost analysis of further join permutations of the tables. If sufficient computational resources are not available, then a determination is made of a restricted subset of remaining join permutations of at least two of the tables for which join costs have not been estimated that is less than all the remaining join permutations. The join costs of permutations of tables in the restricted subset is estimated and the estimated join costs are used to select one join permutation of all the tables having a lowest estimated join cost.

Abstract: In various embodiments, a method, apparatus, and article of manufacture collect statistics in a database management system. A workload comprising a plurality of database queries is received. Query statistics for the database queries are identified. The query statistics for the database queries are consolidated to provide consolidated statistics. One or more statistics collection requests are generated based on the consolidated statistics.

Abstract: A technique for executing a statement in a computer to manipulate data in a data store connected to the computer. Initially, a statement having an aggregate predicate is received. Then, when evaluating the statement, the aggregate predicate is processed to rank data. Furthermore, evaluating includes performing an extended sort operator with early termination.

Abstract: Disclosed is a technique for maintaining statistics. A query is received. Column group generation is performed to form one or more column groups. Column group refinement is performed based on statistics data generated for a previously received query. A statistics check is automatically performed. A statistics collection command is generated to obtain statistics.

Abstract: A method and system for executing a query to access data stored in a database, wherein the query includes a plurality of DISTINCT keys, is disclosed. The method and system of the present invention includes providing a first DISTINCT operation on a first DISTINCT key, storing data fetched from the first DISTINCT operation in a master workfile if more than one sort process is needed to execute the query, and utilizing the master workfile to perform subsequent DISTINCT operations for the other DISTINCT keys.

Abstract: A method and system for Extensible Markup Language (XML) schema validation, includes: loading an XML document into a runtime validation engine, where the runtime validation engine includes an XML schema validation parser; loading an annotated automaton encoding (AAE) for an XML schema definition into the XML schema validation parser; and validating the XML document against the XML schema definition by the XML schema validation parser utilizing the annotated automaton encoding. Each XML schema definition is compiled once into the AAE format, rather than being compiled each time an XML document is validated, and thus significant time is saved. The code for the runtime validation engine is fixed and does not vary depending on the XML schema definition, rather than varying for each XML schema definition, and thus space overhead is minimized. Flexibility in the validation process is provided without compromising performance.

Abstract: According to one aspect of the present invention, a method is provided for processing a query in a database management system that generates an access plan to retrieve desired data from computer storage in response to the query. An identification is derived from at least a portion of a received query or representation thereof. The access plan is generated in consideration of a hint associated with the identification, if such a hint is available from a repository of hints.

Abstract: Provided are a method, system, and program for selecting a join order for tables subject to a join operation. An estimation is made of a join cost to perform joins on permutations of at least two of the tables, wherein each join permutation indicates an order of joining the tables. A determination is made as to whether sufficient computational resources are available to perform a join cost analysis of further join permutations of the tables. If sufficient computational resources are not available, then a determination is made of a restricted subset of remaining join permutations of at least two of the tables for which join costs have not been estimated that is less than all the remaining join permutations. The join costs of permutations of tables in the restricted subset is estimated and the estimated join costs are used to select one join permutation of all the tables having a lowest estimated join cost.

Abstract: Provided are a method, system, an program for tuning a database query. Provided are a base access plan to implement the database query and statistics including information on a layout of the database against which the query will be executed. The statistics are processed to determine performance problems with the base access plan as part of a first analysis of the base access plan and the determined performance problems are processed as part of a second analysis to provide an analysis of the determined performance problems and processing cost of the base access plan. Recommendations are generated to tune the base access plan to improve performance.