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 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 system and method for a computer system having a plurality of DBMS providing a coordinating and assisting function. If a DBMS performs a coordinating function, it is referred to as a coordinating DBMS. If a DBMS performs an assisting function, it is referred to as an assisting DBMS. Each coordinating DBMS receives a query from a user application, decomposes the query into multiple parallel tasks, and allocates the parallel tasks to all of the DBMSs in the system. Each assisting DBMS receives one or more parallel tasks from a coordinating DBMS, executes the parallel tasks and returns the results to the coordinating DBMS. The coordinating DBMSs and assisting DBMSs access one or more storage devices. Furthermore, the present invention comprises a system and method for dynamically disabling a parallel mode on the coordinating DBMSs and the assisting DBMSs.
摘要:
A method, apparatus, and article of manufacture for an index screening system. A query is executed to access data stored on a data storage device connected to a computer. In particular, while accessing one or more indexes to retrieve row identifiers, index matching predicates in the query are applied to select row identifiers and index screening predicates in the query are applied to eliminate one or more selected row identifiers.
摘要:
The system, method, and program of this invention collects multi-column statistics, by a database management system, to reflect a relationship among multiple columns of a table in a relational database. These statistics are stored in the system catalog, and are used during query optimization to obtain an estimate of the number of qualifying rows when a query has predicates on multiple columns of a table.A multi-column linear quantile statistic is collected by dividing the data of multiple columns into sub-ranges where each sub-range has approximately an even distribution of data, and determining a frequency and cardinality of each sub-range. A multi-column polygonal quantile statistic is collected by dividing the data of multiple columns into sub-spaces where each sub-space contains approximately the same number of tuples, and determining a frequency and cardinality of each sub-space.The system catalog is accessed for the stored multi-column linear quantile statistic for a query having a single range predicate and at least one equal predicate to determine the selectivity value for the predicates of the query. The system catalog is accessed for the stored multi-column polygonal quantile statistic for a query having more than one range predicate. These statistics are used in various ways to determine the selectivity value for the predicates of the query.
摘要:
The system, method, and program of this invention collects multi-column statistics, by a database management system, to reflect a relationship among multiple columns of a table in a relational database. These statistics are stored in the system catalog, and are used during query optimization to obtain an estimate of the number of qualifying rows when a query has predicates on multiple columns of a table. A multi-column linear quantile statistic is collected by dividing the data of multiple columns into sub-ranges where each sub-range has approximately an even distribution of data, and determining a frequency and cardinality of each sub-range. A multi-column polygonal quantile statistic is collected by dividing the data of multiple columns into sub-spaces where each sub-space contains approximately the same number of tuples, and determining a frequency and cardinality of each sub-space. The system catalog is accessed for the stored multi-column linear quantile statistic for a query having a single range predicate and at least one equal predicate to determine the selectivity value for the predicates of the query. The system catalog is accessed for the stored multi-column polygonal quantile statistic for a query having more than one range predicate. These statistics are used in various ways to determine the selectivity value for the predicates of the query.
摘要:
A method, apparatus, and article of manufacture for a computer-implemented apportioning system. Work is distributed to processors in a multi-processor system. Initially, during bind-time, a scaling factor is determined for each processor. The scaling factor represents relative processing power in relation to each other processor. Then, portions of a total amount of work are distributed to each processor based on the determined scaling factor of that processor and a determined amount of work for an average processor.
摘要:
A method, apparatus, and article of manufacture for a computer implemented query compiler. A query is executed in a computer, the query being performed by the computer to retrieve data from a database stored on a data storage device connected to the computer. The query is received containing at least one variable. At execution time, a value is determined for each variable in the query. A filter factor is estimated using the determined value for each variable. Then, an access path is determined for the query using the estimated filter factor.
摘要:
A method, apparatus, and article of manufacture for a computer implemented query compiler. A query is executed in a computer, the query being performed by the computer to retrieve data from a database stored on a data storage device connected to the computer. The query is received containing at least one variable. At execution time, a value is determined for each variable in the query. A filter factor is estimated using the determined value for each variable. Then, an access path is determined for the query using the estimated filter factor.
摘要:
A relational data base management system includes a query processor that permits consideration of alternative user-specified access paths, which the processor will validate and incorporate into the query execution plan it otherwise generates. The optimizer of the query processor retrieves user-specified data that defines an access path for a query during bind operations. Any access path parameters that are invalid are replaced with processor-selected values.