Abstract: A query facility for database queries dynamically determines whether selective portions of a database table are likely to benefit from separate query execution strategies, and constructs an appropriate separate execution strategies accordingly. Preferably, the database contains at least one relatively large table comprising multiple partitions, each sharing the definitional structure of the table and containing a different respective discrete subset of the table records. The query facility compares metadata for different partitions to determine whether sufficiently large differences exist among the partitions, and in appropriate cases selects one or more partitions for separate execution strategies. Preferably, partitions are ranked for separate evaluation using a weighting formula which takes into account: (a) the number of indexes for the partition, (b) recency of change activity, and (c) the size of the partition.

Abstract: Embodiments of the invention provide techniques for optimizing database queries for energy efficiency. In general, a query optimizer is configured to compare energy requirements of query plans, and to select a query plan requiring minimal energy to execute. In one embodiment, the query optimizer may also compare time performance of the query plans, and may select a query plan by matching to a user preference for a relative priority between energy requirements and time performance.

Abstract: Methods, systems, and products are provided for code path tracking. Embodiments include identifying an instrumented trace point in software code to be path tracked; identifying a function executed at the instrumented trace point in the software code; identifying parameters for the function executed at the instrumented trace point; and recording a description of the function, the parameters, and the result of the execution of the function using the parameters.

Abstract: Methods, systems, and products are provided for code path tracking. Embodiments include identifying an instrumented trace point in software code to be path tracked; identifying a function executed at the instrumented trace point in the software code; identifying parameters for the function executed at the instrumented trace point; and recording a description of the function, the parameters, and the result of the execution of the function using the parameters.

Abstract: A method, apparatus and program product to optimize a database query. A query plan is generated for the database query where the query plan includes first and second subplans. Cached optimization data associated with the first subplan and generated during evaluation of another query plan for a previous query that uses the first subplan is retrieved. The first subplan is evaluated for resource cost using the retrieved optimization data. The second subplan is also evaluated for resource cost. The query plan is then evaluated for resource cost based upon the evaluations of resource cost for the first and second subplans. A query plan is selected based on evaluations of resource cost and the plan is executed to generate a result set.

Abstract: A method, apparatus and program product dynamically activate and/or deactivate buffers during execution of a database query. The dynamic deactivation and activation is based on the monitoring of information associated with the consumption of data by a plurality of threads during execution of an access plan for the database query. By doing so, the selection of a less optimal buffer position during optimization may be replaced with a more optimal buffer position during runtime, often resulting in improved query performance and parallelism.

Abstract: A process combines multiple grouping sets into single rollup sets with depth lists defining the levels of grouping that must be performed. Grouping sets are identified that are contained within other sets and combined into single rollups with depth lists. Cube aggregation conversion to rollup aggregation is provided for optimizing database query processing. Natural sets of rollup hierarchies within a cube are recognized and the cube is converted into those rollup hierarchies. Once converted, the rollup aggregation is performed to significantly reduce required processing.

Abstract: Embodiments of the invention provide techniques for aggregating database queries for energy efficiency. In one embodiment, queries received by a DBMS are aggregated and staged according to hard-disk drives required for query execution. Each group of queries accessing a given drive may be dispatched for execution together. Further, the queries received by a DBMS may be matched to patterns of previously received queries. The matching patterns may be used to predict other queries which are likely to be received by the DBMS. The received queries may be staged to be dispatched with the predicted queries. By aggregating queries to be executed, access to each hard-disk drive may be optimized, thus reducing the overall energy consumption required for executing the queries.

Abstract: A method, apparatus and program product to optimize a database query. In a first system having a first dataspace, a query plan is generated for the database query. Remote statistics collection associated with the database query is initiated on a second system having a second dataspace. The remote statistics collection uses the second dataspace, which includes a current copy of at least a portion of the first dataspace on the first system. Database statistics are collected for the first system by analyzing the second dataspace and then communicating the collected database statistics to the first system for use in optimizing database queries executed by the first system.

Abstract: A qualitative resource assignment wizard receives qualitative information for a logical partition (LPAR) and calculates computer resource assignments for the LPAR based on the qualitative information and a set of conversion functions. For example, the qualitative resource assignment wizard may calculate a processing unit assignment, a memory assignment, and an I/O slot assignment for the LPAR. The qualitative information may be input by a user, for example, utilizing a graphical user interface (GUI). In one embodiment, the conversion functions are calculated during a training phase, in which a user periodically provides qualitative information while resource usage data is gathered. The wizard may reside in a hardware management console (HMC) or other administrative console and/or may be a component of a hypervisor or other partition management code.

Abstract: A database management system predicts a selectivity for database query conditions requiring a join of records from different tables. The system identifies at least one skewed value in a field specified in the join condition, and constructs, for each skewed value, a set of hypothetical query predicates in which the field specified in the join condition is replaced with a constant equal to the skewed value. The system then predicts the selectivity for the hypothetical predicates, using any appropriate prediction technique. The selectivities of the hypothetical predicates are used to predict a selectivity for the original query.

Abstract: Embodiments of the invention provide techniques for aggregating database queries for energy efficiency. In one embodiment, queries received by a DBMS are aggregated and staged according to hard-disk drives required for query execution. Each group of queries accessing a given drive may be dispatched for execution together. Further, the queries received by a DBMS may be matched to patterns of previously received queries. The matching patterns may be used to predict other queries which are likely to be received by the DBMS. The received queries may be staged to be dispatched with the predicted queries. By aggregating queries to be executed, access to each hard-disk drive may be optimized, thus reducing the overall energy consumption required for executing the queries.

Abstract: Techniques for optimizing database queries for energy efficiency. A query optimizer is configured to compare energy requirements of query plans, and to select a query plan requiring minimal energy to execute. The query optimizer may also compare time performance of the query plans, and may select a query plan by matching to a user preference for a relative priority between energy requirements and time performance.

Abstract: A plan for executing a query in a relational database is obtained. A query for accessing data in the relational database is received. The query specifies N tables in the relational database from which data is to be retrieved. A determination is made whether a syntax of the query matches a syntax of a plan in a plan cache for executing the query. Matches are identified between generic table formats of the N tables specified in the query to generic table formats of N tables specified in the plan responsive to the syntax of the query matching the syntax of a plan in the plan cache for executing the query. The plan for executing the query is obtained based on whether the syntax of the query matches the syntax of the plan and based on identified matches between the generic table formats of the N tables specified in the query to the generic table formats of the N tables specified in the plan.

Abstract: A method, apparatus and program product is provided for optimizing a database query. A query syntax, system generated predicates, and requisite statistics of the database query are analyzed to determine if a predicate structure is a good candidate for a symbol table only data structure. The predicate structure is analyzed to determine if the predicate structure is already encompassed by an encoded vector index. The symbol table only data structure is generated for at least one column in a database table without generating a corresponding vector data structure from an encoded vector index if the predicate structure is a good candidate and not encompassed by an encoded vector index. The symbol table only data structure is maintained by detecting a change in data associated with the symbol table only data structure and updating the symbol table only data structure to reflect the change in the data.

Abstract: A method, apparatus and program product is provided for optimizing a database query. A query syntax, system generated predicates, and requisite statistics of the database query are analyzed to determine if a predicate structure is a good candidate for a symbol table only data structure. The predicate structure is analyzed to determine if the predicate structure is already encompassed by an encoded vector index. The symbol table only data structure is generated for at least one column in a database table without generating a corresponding vector data structure from an encoded vector index if the predicate structure is a good candidate and not encompassed by an encoded vector index. The symbol table only data structure is maintained by detecting a change in data associated with the symbol table only data structure and updating the symbol table only data structure to reflect the change in the data.

Abstract: A method, apparatus, and program product are provided for preserving a query plan cache on a backup system having a dataspace containing a copy of data and a copy of a query plan cache from a production system. An update is initiated of at least a portion of the copy of the data on the backup system with a portion of the data on the production system. A merge is initiated of updated query plans in the query plan cache from the production system with corresponding query plans in the copy of the query plan cache on the backup system. Objects are correlated in the updated query plans in the copy of the query plan cache with the updated copy of the data on the backup system.

Abstract: A method, apparatus and program product is provided for optimizing a database query. A query syntax, system generated predicates, and requisite statistics of the database query are analyzed to determine if a predicate structure is a good candidate for a symbol table only data structure. The predicate structure is analyzed to determine if the predicate structure is already encompassed by an encoded vector index. The symbol table only data structure is generated for at least one column in a database table without generating a corresponding vector data structure from an encoded vector index if the predicate structure is a good candidate and not encompassed by an encoded vector index. The symbol table only data structure is maintained by detecting a change in data associated with the symbol table only data structure and updating the symbol table only data structure to reflect the change in the data.

Abstract: A method, apparatus, system, and signal-bearing medium that, in an embodiment, determine performance data for query optimization of a query directed to a database table having multiple partitions. The performance data for the query optimization is presented in a user interface, and an option is provided in the user interface to create a non-spanning index for any of the partitions mentioned in the performance data.

Abstract: Embodiments of the invention provide techniques for maintaining I/O value caches for database queries. Each maintained cache may be configured for use with a particular database query. Each cache may be persistently maintained in a system, meaning the cache is not automatically deleted after some period of time, and may thus be used to process subsequent instances of the same query. By use of the maintained cache, executing subsequent instances of the query may be avoided, thus saving time and system resources. Further, the maintained cache may be adapted to process other queries having similar characteristics to the initial query. The data included in each cache may be refreshed as required by changes to the underlying data.