摘要:
Techniques are provided that determine that a query includes at least one subquery that may be correlated or decorrelated. An internal representation of the query that represents the subquery in both correlated and decorrelated form is generated, wherein the internal representation includes at least one virtual table.
摘要:
Techniques are provided that determine that a query includes at least one subquery that may be correlated or decorrelated. An internal representation of the query that represents the subquery in both correlated and decorrelated form is generated, wherein the internal representation includes at least one virtual table.
摘要:
Techniques are provided that determine that a query includes at least one subquery that may be correlated or decorrelated. An internal representation of the query that represents the subquery in both correlated and decorrelated form is generated, wherein the internal representation includes at least one virtual table.
摘要:
A method and system for providing a scalable storage scheme for native hierarchically structured data of relational tables, includes a base table with indicator columns with information pertaining to hierarchically structured data of a document, data tables for storing the hierarchically structured data corresponding to the indicator columns, and node identifier indexes corresponding to the data tables for mapping between the indicator columns and the hierarchically structured data in the data tables. In an embodiment, actual data for each hierarchically structured data (such as XML) column is stored in a separate data table, and each data table has a separate node identifier index. The node identifier index is searched with a key containing the document identifier and a logical node identifier is used, and a record identifier of a record in the data table containing the node assigned the logical node identifier is retrieved.
摘要:
A method, apparatus and article for manufacture for generating static, dynamic and hybrid sparse indices for use with workfiles used by SQL queries in a relational database management system. A workfile and a sparse index structure are temporarily created in the computer during execution of the query by the computer. The workfile stores intermediate relations resulting from execution of a portion of the SQL query, wherein the intermediate relations comprise sorted rows for an inner table referenced in the SQL query. The sparse index structure contains one or more entries indicating at least an approximate location for at least some of the rows in the workfile. As one or more rows from an outer table referenced in the SQL query are retrieved, the entries of the sparse index structure are searched for a closest matching entry for each retrieved row. The sorted workfile is then scanned for a row matching each retrieved row using the closest matching entry from the sparse index structure as a starting position. The sparse index structure is then updated with an entry corresponding to the row from the sorted workfile matching the retrieved row from the outer table.
摘要:
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.
摘要:
A method and apparatus for generating static, dynamic and hybrid sparse indices for use with workfiles used by SQL queries in a relational database management system.
摘要:
A method and system for providing a scalable storage scheme for native hierarchically structured data of relational tables, includes a base table with indicator columns with information pertaining to hierarchically structured data of a document, data tables for storing the hierarchically structured data corresponding to the indicator columns, and node identifier indexes corresponding to the data tables for mapping between the indicator columns and the hierarchically structured data in the data tables. In an embodiment, actual data for each hierarchically structured data (such as XML) column is stored in a separate data table, and each data table has a separate node identifier index. The node identifier index is searched with a key containing the document identifier and a logical node identifier is used, and a record identifier of a record in the data table containing the node assigned the logical node identifier is retrieved.
摘要:
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.
摘要:
Disclosed is a method, system, and program for performing a join operation on a multi-column table and at least two satellite tables having a join condition. Each satellite table is comprised of multiple rows and at least one join column. The multi-column table is comprised of multiple rows and at least one column corresponding to the join column in each satellite table. A join operation is performed on the rows of the satellite tables to generate concatenated rows of the satellite tables. One of the concatenated rows is joined to the multi-column table and a returned entry from the multi-column table is received. A determination is then made as to whether the returned entry matches the search criteria. If so, a determination is made as to whether one of the satellite tables has duplicates of values in the join column of the returned matching entry or the multi-column table has duplicate entries in the join columns. Returned matching entries are generated for each duplicate value in the satellite tables and duplicate entry in the multi-column table.