Abstract: Techniques are disclosed hereafter for efficiently enforcing a “WITHOUT OVERLAP” range constraint by confirming primary-key integrity for a new or modified row (the “target row”) by checking just two neighboring index entries, using a new “two-sided halted range scan” of the same key index on entities which have range-endpoints data as part of their primary key. Techniques are described for reducing search time and resources in situations where a query specifies an entity and a point within a non-overlapping range. Techniques are also described for optimized handling of queries that do not specify a primary key but have both a range condition and a filter on a non-key column.

Abstract: Systems and methods for organizing a structured query language statement execution plan to increase the efficiency of a computer device in executing the statement. A data structure is created in computer memory that encodes information about a database statement execution plan (e.g., an SQL statement). The information is arranged in a specific logical structure and may be displayed graphically as a query diagram. The data structure is used in optimizing the SQL statement execution plan so as to merge joined tables to enable efficient optimization. Furthermore optimized SQL execution plans in accordance with the present invention proportionally scale with the number of rows returned from a query, do not depend unnecessarily on potentially unavailable central resources (e.g., sort space), scale in the event that optimizer statistics and assumptions are poor, and make use of processing and memory resources.

Abstract: In a database table with rows each having respective key values, the locking of a key value to enforce key-value uniqueness is accomplished by (a) mapping the key value into a set of hash values to produce a resulting hash value, and (b) locking all key values (i.e., preventing writing of key values in new rows and preventing updates creating new key values in existing rows) that map into the resulting hash value. This provides a compromise between the high-granularity and high-cost solution of indexing, and the low-cost but very low-granularity solution of table-level locking. One useful application of this technique lies in the enforcement of uniqueness of multi-column keys in the table without incurring the cost of indexing all possible combinations of column values that might comprise key values.

Abstract: A method of constructing an aid to tuning of database statements comprises a data structure (stored in a memory on a computer system) which compactly represents that information which is needed about a database statement to determine the optimal series of operations (e.g., table data fetches) needed to execute the statement. The information includes the relationships between tables joined in the statement and the selectivities of logical conditions applied to rows in those tables.