Abstract: Database management systems and methods for searching a database are disclosed. In one embodiment, an inspector examines a plan cache or a program containing embedded queries. A plurality of similar queries is identified, and an alias is generated that satisfies the plurality of queries. The alias may be executed on a database to output a result set. Queries belonging to the alias may be executed on the result set of the alias, rather than on the database. Accordingly, efficiency is improved and runtime costs are reduced as compared to conventional database management systems.

Abstract: An apparatus and method to optimize a query access plan in a computer database system. In preferred embodiments, the query optimizer determines the query can be optimized and generates for the query an optimized access plan that eliminates records defined by a Where clause and one or more ordering criteria prior to ordering the records (sorting or grouping) and then returning a first n rows.

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: A method, apparatus, system, and signal-bearing medium that, in an embodiment, estimate a number of rows that a recursive query will retrieve from a table by recursively probing an index associated with the table. A recursive query includes a seed and a recursive predicate, each of which is associated with a respective column in the table. If the index has a leading column that matches the table column associated with the seed, and the index has a secondary column that matches the table column associated with the recursive predicate, then the index is recursively probed until a threshold depth of the recursive probing is reached or until all nodes of the index have been examined.

Abstract: A database engine and a system running a database engine utilize a dynamic join reordering feature to change the order of two or more join operations while a query is executing. The database engine starts execution of the query with an initial join order setting but monitors the execution of the query to determine whether the initial join order or some other join order would provide better runtime performance. If another join order would provide better performance, then the database engine can change the join order during query execution and complete the query using the new join order.

Abstract: A database query optimizer determines when no optimal index for a query exists, determines whether a sub-optimal index exists, and if so, uses statistical information for each additional key in the sub-optimal index to rewrite the query in a manner that allows traversing the sub-optimal index. The sub-optimal index is then probed using the rewritten query, and the number of estimated returned rows is then used to optimize the query.

Abstract: An apparatus, program product and method utilize the retrieval status of a resource to generate an access plan for a database query that uses the resource. The retrieval status, which indicates, for example, what percentage of a given resource is already stored in working memory, and thus need not be separately retrieved during query execution, may be used to generate more accurate input/output cost estimates for access plans, and thus enable a query optimizer to better select an access plan that is optimal under given runtime conditions.

Abstract: A method, apparatus and computer program product are provided for implementing autonomic testing and verification of software fix programs or program temporary fixes (PTFs). A software fix program including multiple patches or a program temporary fix (PTF) including multiple programs is received. Each patch or program of the multiple patches or multiple programs of the software fix program or PTF is sequentially applied to a software product. The software product is tested responsive to each sequentially applied patch or program. Then next iterations or different combinations of patches or programs are sequentially applied to a software product and then the software product is tested responsive to each of the applied iterations.

Abstract: A method, a query optimizer, and computer program product are provided for implementing live switchover to a temporary sparse index for faster query performance. A first plan using an existing index is used for processing a query. A temporary sparse index is built for the query simultaneously with the first plan processing the query. When the temporary sparse index is built, processing the query with the first plan is stopped and a live switchover to the temporary sparse index is provided. Then a second plan using the temporary sparse index is used to continue processing the query at a point where processing stopped with the first plan.

Abstract: A method, apparatus and system that in an embodiment detect that a trigger exists, where the trigger indicates a potential need to rebuild a saved query access plan, and determine whether a previous job associated with the trigger created a new access plan that was identical to the saved access plan. If a previous job associated with the trigger has already created the new access plan and found that it was identical to the saved access plan, then the query is performed with the saved access plan, since there is no advantage to be gained by creating the new access plan again. In this way, multiple jobs are kept from repeatedly re-creating an access plan that is identical to one that already exists.

Abstract: Disclosed is an apparatus, method, and program product for performing efficient database access plan caching. Unlike prior art mechanism that automatically discard stored access plans whenever the need for a different access plans is detected, stored plans are intelligently retained despite the handling of one or more infrequent queries that call for the use of a different plan.

Abstract: A method, a query optimizer, and computer program product are provided for implementing live switchover to a temporary sparse index for faster query performance. A first plan using an existing index is used for processing a query. A temporary sparse index is built for the query simultaneously with the first plan processing the query. When the temporary sparse index is built, processing the query with the first plan is stopped and a live switchover to the temporary sparse index is provided. Then a second plan using the temporary sparse index is used to continue processing the query at a point where processing stopped with the first plan.

Abstract: Disclosed is an apparatus, method, and program product for performing efficient database access plan caching. Unlike prior art mechanism that automatically discard stored access plans whenever the need for a different access plans is detected, stored plans are intelligently retained despite the handling of one or more infrequent queries that call for the use of a different plan.