Abstract: Techniques are disclosed for generating statistical views in a database system. In one embodiment, a request is received to execute a database workload. One or more constraints pertaining to executing the database workload is retrieved. The database workload is evaluated to generate multiple statistical view candidates. The statistical view candidates are refined based on the one or more constraints. One or more statistical views are then generated based on the refined statistical view candidates.

Abstract: Tuning a production database system through the use of a remote mimic. In response to receipt of a query tuning request against a database system, information about that system is obtained and a mimic of the system is set up in a remote system environment. The mimic aims to imitate the database system in all relevant ways with respect to the tuning request. A tuning analysis is then performed on this mimic system such that there is substantially no impact to operations of the original database system. Tuning results are then applied to the original database system. The entire process takes place with little or no human intervention.

Abstract: Tuning a production database system through the use of a remote mimic. In response to receipt of a query tuning request against a database system, information about that system is obtained and a mimic of the system is set up in a remote system environment. The mimic aims to imitate the database system in all relevant ways with respect to the tuning request. A tuning analysis is then performed on this mimic system such that there is substantially no impact to operations of the original database system. Tuning results are then applied to the original database system. The entire process takes place with little or no human intervention.

Abstract: Techniques are disclosed for generating statistical views in a database system. In one embodiment, a request is received to execute a database workload. One or more constraints pertaining to executing the database workload is retrieved. The database workload is evaluated to generate multiple statistical view candidates. The statistical view candidates are refined based on the one or more constraints. One or more statistical views are then generated based on the refined statistical view candidates.

Abstract: Tuning a production database system through the use of a remote mimic. In response to receipt of a query tuning request against a database system, information about that system is obtained and a mimic of the system is set up in a remote system environment. The mimic aims to imitate the database system in all relevant ways with respect to the tuning request. A tuning analysis is then performed on this mimic system such that there is substantially no impact to operations of the original database system. Tuning results are then applied to the original database system. The entire process takes place with little or no human intervention.

Abstract: Tuning a production database system through the use of a remote mimic. In response to receipt of a query tuning request against a database system, information about that system is obtained and a mimic of the system is set up in a remote system environment. The mimic aims to imitate the database system in all relevant ways with respect to the tuning request. A tuning analysis is then performed on this mimic system such that there is substantially no impact to operations of the original database system. Tuning results are then applied to the original database system. The entire process takes place with little or no human intervention.

Abstract: Techniques are disclosed for generating statistical views in a database system. In one embodiment, a request is received to execute a database workload. One or more constraints pertaining to executing the database workload is retrieved. The database workload is evaluated to generate multiple statistical view candidates. The statistical view candidates are refined based on the one or more constraints. One or more statistical views are then generated based on the refined statistical view candidates.

Abstract: A method, computer readable medium, and system for optimizing a query in a relational database processing system is disclosed. The present invention relates to a query rewrite optimization method for eliminating a redundant join and equivalent subquery in an SQL query before generation and selection of the optimal query execution plan. The method of the present invention includes evaluating the query to identify a join predicate joining a sub-expression of the query to itself, and determining whether a row set producible from a first set of references of the query to the sub-expression is subsumed by a row set producible from a second set of references of the query to the sub-expression. Based on such evaluation and determination, the query may be reformed to eliminate the join predicate and the second quantifier. A further determination of the removability of the second quantifier may be required such as by evaluating a cardinality constraint when query output cardinality is material.

Abstract: The invention herein provides method and apparatus, including software for determining a set of materialized views or indices of the contents or a subset of the contents of a database in a data processing system to be created for one or more users of the database. The method and apparatus provide method and means for evaluating a workload presented by a user to the database; evaluating the data processing system characteristics; evaluating the database characteristics; and, using the above evaluations for recommending a set of suitable materialized views or indices to the user.

Abstract: An index structure for use by a database management system comprises a variant of a Patricia tree, wherein each node stores a column value that identifies a specified column of the constructed n-column search key that is used to determine a next path taken through the tree, a null value N that specifies whether a null value or an actual data value of the specified column of the constructed n-column search key is used to determine the next path taken through the tree, and a position value that specifies a portion of the specified column from the constructed n-column search key to be used to determine the next path taken through the tree when the actual data value of the specified column of the constructed n-column search key is used to determine the next path taken through the tree.

Abstract: An index structure for use by a database management system comprises a variant of a Patricia tree, wherein each node stores a column value that identifies a specified column of the constructed n-column search key that is used to determine a next path taken through the tree, a null value N that specifies whether a null value or an actual data value of the specified column of the constructed n-column search key is used to determine the next path taken through the tree, and a position value that specifies a portion of the specified column from the constructed n-column search key to be used to determine the next path taken through the tree when the actual data value of the specified column of the constructed n-column search key is used to determine the next path taken through the tree.

Abstract: A method, computer readable medium, and system for optimizing a query in a relational database processing system is disclosed. The present invention relates to a query rewrite optimization method for eliminating a redundant join and equivalent subquery in an SQL query before generation and selection of the optimal query execution plan. The method of the present invention includes evaluating the query to identify a join predicate joining a sub-expression of the query to itself, and determining whether a row set producible from a first set of references of the query to the sub-expression is subsumed by a row set producible from a second set of references of the query to the sub-expression. Based on such evaluation and determination, the query may be reformed to eliminate the join predicate and the second quantifier. A further determination of the removability of the second quantifier may be required such as by evaluating a cardinality constraint when query output cardinality is material.

Abstract: The invention herein provides method and apparatus, including software for determining a set of materialized views or indices of the contents or a subset of the contents of a database in a data processing system to be created for one or more users of the database. The method and apparatus provide method and means for evaluating a workload presented by a user to the database; evaluating the data processing system characteristics; evaluating the database characteristics; and, using the above evaluations for recommending a set of suitable materialized views or indices to the user.

Abstract: The present invention optimizes SQL queries by exploiting uniqueness properties. In identifying whether the generalized 1-tuple condition exists, the query is first analyzed to determine whether any columns referenced in a predicate of the query are bound. According to the present invention, columns may be bound to constant values or correlated columns or columns that are already bound. The bound columns, if any, are then analyzed to determine whether any of the bound columns comprise a key for its associated table. If these conditions exist, then the query satisfies the 1-tuple condition, in that it returns at most one tuple. Once the generalized 1-tuple condition has been identified to exist for the query, important query transformations can be performed for optimization purposes. These query transformations comprise the transformation of scalar subqueries into joins, or the elimination of distinctiveness requirements (i.e., DISTINCT keywords) from SELECT clauses.

Abstract: A method and apparatus for optimizing SQL queries by propagating and exploiting column nullability. Column nullability is identified and propagated using a three-valued logic, wherein a column of a table can be identified nullability information is exploited to optimize query operations through transformations. In one aspect of the present invention, quantified predicates (such as ">ALL") are transformed into simple predicates involving singleton subqueries so that indexing can be exploited. In another aspect of the present invention, "is not null" predicates are generated and pushed for certain aggregate queries. In still another aspect of the present invention, intersect operations are transformed into joins. The end result is that the present invention can significantly enhance the performance of the queries.

Abstract: A system for optimizing SQL queries in a relational database management system using magic decorrelation. After representing an assembly of multiple SQL queries in computer memory using data structures configured in the query box representation ("QBR") format, queries amenable to decorrelation are identified, and FEED and ABSORB stages are applied to rewrite the QBR in decorrelated form. The FEED stage generates a set of correlation values that the subquery can use to decorrelate. The ABSORB stage decorrelates the subquery using the correlation values prepared by the FEED stage, resulting in the correlation bindings being absorbed into the subquery. The invention thereby takes full advantage of set-at-a-time, rather than tuple-at-a-time, processing.

Abstract: A method and apparatus for optimizing SQL queries in a relational database management system uses early-out join transformations. An early-out join comprises a many-to-one existential join, wherein the join scans an inner table for a match for each row of the outer table and terminates the scan for each row of the outer table when a single match is found in the inner table. To transform a many-to-many join to an early-out join, the query must include a requirement for distinctiveness, either explicitly or implicitly, in one or more result columns for the join operation. Distinctiveness can be specified using the DISTINCT keyword in the SELECT clause or can be implied from the predicates present in the query. The early-out join transformation also requires that no columns of the inner table be referenced after the join, or if an inner table column is referenced after the join, that each referenced column be "bound".

Abstract: A method and apparatus for optimizing SQL queries in a relational database management system uses early-out join transformations. An early-out join comprises a many-to-one existential join, wherein the join scans an inner table for a match for each row of the outer table and terminates the scan for each row of the outer table when a single match is found in the inner table. To transform a many-to-many join to an early-out join, the query must include a requirement for distinctiveness, either explicitly or implicitly, in one or more result columns for the join operation. Distinctiveness can be specified using the DISTINCT keyword in the SELECT clause or can be implied from the predicates present in the query. The early-out join transformation also requires that no columns of the inner table be referenced after the join, or if an inner table column is referenced after the join, that each referenced column be "bound".