Abstract: Computer-implemented systems and associated operating methods use atomic query maps to identify and evaluate database query plan robustness landmarks. The computer-implemented system comprises logic that evaluates robustness of a selected atomic query by measuring performance of atomic query execution in a predetermined range of runtime conditions that include data characteristics. The logic produces a set of measurements that can be displayed as one or more performance maps and analyzes the measured performance to identify landmarks indicative of database atomic query performance degradation greater than a predetermined amount.

Abstract: Mechanisms and techniques for database fragment cloning and management are provided. A database object, such as a table, rowset or index, is divided into fragments. Each fragment is cloned to create cloned fragments, which operationally are substantially identical to one another. One or more of the cloned fragments may be designated as a primary cloned fragment for performing database operations or as a secondary cloned fragment for serving as backup. Updates to each fragment are implemented on the primary cloned fragment and are then propagated from the primary cloned fragment to the corresponding secondary cloned fragments. A cloned fragment can go offline, becoming unavailable to be updated. When the cloned fragment returns online, the cloned fragment is refreshed with data included in the primary cloned fragment. While being refreshed, the cloned fragment may continue to be updated.

Abstract: Computer-implemented systems and associated operating methods use atomic query maps to identify and evaluate database query plan robustness landmarks. The computer-implemented system comprises logic that evaluates robustness of a selected atomic query by measuring performance of atomic query execution in a predetermined range of runtime conditions that include data characteristics. The logic produces a set of measurements that can be displayed as one or more performance maps and analyzes the measured performance to identify landmarks indicative of database atomic query performance degradation greater than a predetermined amount.

Abstract: Method and apparatus for optimizing the processing of join queries based on join cardinality. Embodiments implement the methods in query optimizers in relational database management systems. A good join order for a multiple join query is found with a metric that compares the relative merits of candidate join orders as a whole. Embodiments estimate the join selectivity of foreign key--foreign key joins, where both participating tables are foreign keys with respect to a primary or unique key of one primary table. A graph representation of a query is processed to estimate the join cardinality of an arbitrarily large number of filters and joins, including any combination of primary key--foreign key joins and foreign key--foreign key joins.

Abstract: A computer implemented method for generating a response to a join. Two tables are divided into fragments. A join fragment map identifies, for each respective fragment from the first table, the fragments from the second table which contain a record that satisfies the join predicate with a record from the respective fragment from the first table. The map is used to eliminate fragments which cannot satisfy the join predicate.

Abstract: The semantics of the outer join operator are extended to permit the application of different predicates to the join tuples and the anti-join tuples. For un-nesting of nested query blocks, the anti-join tuples, for example, are associated with a count value of zero instead of a count value of null. An inner query block is un-nested from an outer query block by converting the inner query to a first un-nested query generating a temporary relation and converting the outer query block to a second un-nested query receiving the precomputed temporary relation.