Abstract: Provided are techniques for efficient subquery predicate generation to reduce processing in a multi-table join. It is determined that a query is to be rewritten, wherein the query includes a predicate for a first column of a first table and a second column of a second table. The query is rewritten with generated subquery predicates for the first table that are to be applied to the second table and with generated subquery predicates for the second table that are to be applied to the first table. Minimum and maximum ranges for columns of the generated subquery predicates at a cursor open are determined. The minimum and maximum ranges are merged to determine inclusive ranges that exist in the first table and the second table. The generated subquery predicates are rewritten as derived local subquery predicates with the inclusive ranges. The query with the derived local subquery predicates is executed.

Abstract: A method, system and computer program product are provided. A first index scan of records of a database table is performed. A first index used by the first index scan is specified in a DBMS query statement as being ordered by one or more field values of one or more fields of the first index. A second scan of the database table is performed to determine whether each respective record of the second scan is qualified based on one or more fields of the each respective record of the second scan and a predicate. A lookup data structure is built indicating whether each of the respective records of the second scan is qualified. The lookup data structure is used to determine whether a record of the first index scan is qualified when the lookup data structure becomes available.

Abstract: A method, a computer program product and a system are provided. A case expression is analyzed for redundant expressions, patterns equivalent to a built-in function, and specific functions to form a simplified expression, wherein the case expression is written in a language supported by a database management system. The simplified expression is optimized based on a cost benefit evaluation of no optimization, native code generation, hashing inputs, and a results caching algorithm to form an execution plan. The execution plan is utilized in the database management system for the case expression.

Abstract: Provided are techniques for efficient subquery predicate generation to reduce processing in a multi-table join. It is determined that a query is to be rewritten, wherein the query includes a predicate for a first column of a first table and a second column of a second table. The query is rewritten with generated subquery predicates for the first table that are to be applied to the second table and with generated subquery predicates for the second table that are to be applied to the first table. Minimum and maximum ranges for columns of the generated subquery predicates at a cursor open are determined. The minimum and maximum ranges are merged to determine inclusive ranges that exist in the first table and the second table. The generated subquery predicates are rewritten as derived local subquery predicates with the inclusive ranges. The query with the derived local subquery predicates is executed.

Abstract: Provided are techniques for efficient subquery predicate generation to reduce processing in a multi-table join. It is determined that a query is to be rewritten, wherein the query includes a predicate for a first column of a first table and a second column of a second table. The query is rewritten with generated subquery predicates for the first table that are to be applied to the second table and with generated subquery predicates for the second table that are to be applied to the first table. Minimum and maximum ranges for columns of the generated subquery predicates at a cursor open are determined. The minimum and maximum ranges are merged to determine inclusive ranges that exist in the first table and the second table. The generated subquery predicates are rewritten as derived local subquery predicates with the inclusive ranges. The query with the derived local subquery predicates is executed.

Abstract: Provided are techniques for efficient subquery predicate generation to reduce processing in a multi-table join. It is determined that a query is to be rewritten, wherein the query includes a predicate for a first column of a first table and a second column of a second table. The query is rewritten with generated subquery predicates for the first table that are to be applied to the second table and with generated subquery predicates for the second table that are to be applied to the first table. Minimum and maximum ranges for columns of the generated subquery predicates at a cursor open are determined. The minimum and maximum ranges are merged to determine inclusive ranges that exist in the first table and the second table. The generated subquery predicates are rewritten as derived local subquery predicates with the inclusive ranges. The query with the derived local subquery predicates is executed.

Abstract: Provided are techniques for progressive optimization for implicit CAST predicates. In response to receiving a query with an original predicate comparing a character value of a character data type to a literal value of a numeric data type, a number of iterations is set to a length of the character data type. For each of the number of iterations, prefix predicates are generated based on that iteration and processed to identify a qualified index key in an index. Once the iterations are completed, the character value and the literal value are normalized. The original predicate with the normalized character value and the normalized literal value is applied starting at the qualified index key identified in a last iteration to generate a result set for the query. The result set is returned.

Abstract: Disclosed aspects relate to index maintenance management of a relational database management system having a set of indexes. A subset of the set of indexes, which is indicated as a non-critical index subset, is detected with respect to the set of indexes. Related to maintenance of the subset of the set of indexes, a determination is made to perform an index maintenance impact action. Corresponding to the subset of the set of indexes, the index maintenance impact action is performed.

Abstract: An access plan including multiple indexes is selected for accessing data of a database system. A filtering status of each index within the selected access plan is determined based on information available at execution of the selected access plan. The order of the indexes within the selected access plan is modified based on the filtering status of the indexes, and the selected access plan is executed with the modified order of the indexes. The execution of the selected access plan is interrupted in response to accessing a threshold amount of data and the filtering of the indexes of the selected access plan is estimated. A processing order for the indexes is determined based on the estimated filtering. The execution of the selected access plan resumes based on the determined processing order.

Abstract: A method, system and computer program product are provided. A first index scan of records of a database table is performed. A first index used by the first index scan is specified in a DBMS query statement as being ordered by one or more field values of one or more fields of the first index. A second scan of the database table is performed to determine whether each respective record of the second scan is qualified based on one or more fields of the each respective record of the second scan and a predicate. A lookup data structure is built indicating whether each of the respective records of the second scan is qualified. The lookup data structure is used to determine whether a record of the first index scan is qualified when the lookup data structure becomes available.

Abstract: A method, a computer program product and a system are provided. A case expression is analyzed for redundant expressions, patterns equivalent to a built-in function, and specific functions to form a simplified expression, wherein the case expression is written in a language supported by a database management system. The simplified expression is optimized based on a cost benefit evaluation of no optimization, native code generation, hashing inputs, and a results caching algorithm to form an execution plan. The execution plan is utilized in the database management system for the case expression.

Abstract: A method, a computer program product and a system are provided. A case expression is analyzed for redundant expressions, patterns equivalent to a built-in function, and specific functions to form a simplified expression, wherein the case expression is written in a language supported by a database management system. The simplified expression is optimized based on a cost benefit evaluation of no optimization, native code generation, hashing inputs, and a results caching algorithm to form an execution plan. The execution plan is utilized in the database management system for the case expression.

Abstract: A method, system and computer program product are provided. A first index scan of records of a database table is performed. A first index used by the first index scan is specified in a DBMS query statement as being ordered by one or more field values of one or more fields of the first index. A second scan of the database table is performed to determine whether each respective record of the second scan is qualified based on one or more fields of the each respective record of the second scan and a predicate. A lookup data structure is built indicating whether each of the respective records of the second scan is qualified. The lookup data structure is used to determine whether a record of the first index scan is qualified when the lookup data structure becomes available.

Abstract: Provided are techniques for progressive optimization for implicit CAST predicates. In response to receiving a query with an original predicate comparing a character value of a character data type to a literal value of a numeric data type, a number of iterations is set to a length of the character data type. For each of the number of iterations, prefix predicates are generated based on that iteration and processed to identify a qualified index key in an index. Once the iterations are completed, the character value and the literal value are normalized. The original predicate with the normalized character value and the normalized literal value is applied starting at the qualified index key identified in a last iteration to generate a result set for the query. The result set is returned.

Abstract: A method, system and computer program product are provided. A first index scan of records of a database table is performed. A first index used by the first index scan is specified in a DBMS query statement as being ordered by one or more field values of one or more fields of the first index. A second scan of the database table is performed to determine whether each respective record of the second scan is qualified based on one or more fields of the each respective record of the second scan and a predicate. A lookup data structure is built indicating whether each of the respective records of the second scan is qualified. The lookup data structure is used to determine whether a record of the first index scan is qualified when the lookup data structure becomes available.

Abstract: Provided are techniques for efficient subquery predicate generation to reduce processing in a multi-table join. It is determined that a query is to be rewritten, wherein the query includes a predicate for a first column of a first table and a second column of a second table. The query is rewritten with generated subquery predicates for the first table that are to be applied to the second table and with generated subquery predicates for the second table that are to be applied to the first table. Minimum and maximum ranges for columns of the generated subquery predicates at a cursor open are determined. The minimum and maximum ranges are merged to determine inclusive ranges that exist in the first table and the second table. The generated subquery predicates are rewritten as derived local subquery predicates with the inclusive ranges. The query with the derived local subquery predicates is executed.

Abstract: An access plan including multiple indexes is selected for accessing data of a database system. A filtering status of each index within the selected access plan is determined based on information available at execution of the selected access plan. The order of the indexes within the selected access plan is modified based on the filtering status of the indexes, and the selected access plan is executed with the modified order of the indexes. The execution of the selected access plan is interrupted in response to accessing a threshold amount of data and the filtering of the indexes of the selected access plan is estimated. A processing order for the indexes is determined based on the estimated filtering. The execution of the selected access plan resumes based on the determined processing order.

Abstract: Provided are techniques for efficient subquery predicate generation to reduce processing in a multi-table join. It is determined that a query is to be rewritten, wherein the query includes a predicate for a first column of a first table and a second column of a second table. The query is rewritten with generated subquery predicates for the first table that are to be applied to the second table and with generated subquery predicates for the second table that are to be applied to the first table. Minimum and maximum ranges for columns of the generated subquery predicates at a cursor open are determined. The minimum and maximum ranges are merged to determine inclusive ranges that exist in the first table and the second table. The generated subquery predicates are rewritten as derived local subquery predicates with the inclusive ranges. The query with the derived local subquery predicates is executed.

Abstract: A method, a computer program product and a system are provided. A case expression is analyzed for redundant expressions, patterns equivalent to a built-in function, and specific functions to form a simplified expression, wherein the case expression is written in a language supported by a database management system. The simplified expression is optimized based on a cost benefit evaluation of no optimization, native code generation, hashing inputs, and a results caching algorithm to form an execution plan. The execution plan is utilized in the database management system for the case expression.

Abstract: In an index-only multi-index access in a database, when a query to be executed requires multiple indexes, a query optimizer determines whether columns are needed for a query result, subquery, or inner join result. If not, then the query result is resolved using qualified record identifiers (RIDs) from the multiple indexes without accessing the data pages. When the columns are needed and can be resolved using input values of the query, then the query result is resolved using the qualified RIDs from the multiple indexes and substituting column values with the input values of the query. When the columns are needed and cannot be resolved using the input values of the query, the query optimizer may store one or more index keys with its corresponding qualified RIDs from the multiple indexes and may resolve the query result using the stored index keys without accessing the data pages of the database.