Abstract: Indoubt transaction entries are recorded for each member of a database cluster, thereby avoiding the CPU cost and elapsed-time impact of persisting this information to a disk (either via a log write or a relational table I/O). This implementation allows for full read/write access and data coherency for concurrent access by all the members in the database cluster. At any given point in time, a full list of indoubt transactions is maintained for the entire database cluster in a relational table (e.g., an SQL table).

Abstract: A method, apparatus, and article of manufacture for analyzing a query and extending an access path selection for the query, in order to optimize joined table expressions and complex join operations in the query. The extension of the access path selection occurs in two phases: (1) an access path selection router analyzes and divides the query into portions, so that the overall access path selection is divided into smaller access path selections for processing by a join enumerator; and (2) the join enumerator is provided to handle joined table expressions and complex join operators, wherein the join enumerator can be continuously enhanced as more powerful query optimization techniques become available.

Abstract: A query optimizer analyzes a query and triggers a sequence of transformations to achieve optimal performance for joined table expressions. The transformations include pushing down predicates for joined table expressions and pushing down non-null predicates to simplify join operators for joined table expressions.