摘要:
A system and method including a computer shape definition language are disclosed for defining shapes and mining time sequences that resemble the shapes. The system and method include provisions for establishing a user-defined alphabet that in turn establishes a set of elemental shapes. The system also includes simple yet powerful operators for combining the elemental shapes to define a desired time sequence shape. Moreover, intervals of actual time sequences are mapped into corresponding transition sequences using the alphabet, and the transition sequences are stored in a hierarchical index structure for easily accessing the transition sequences. The index structure is entered with the desired time sequence shape, and the index structure is traversed to identify maximal actual transition sequences which conform to the desired time sequence shape, within user-definable blurry criteria.
摘要:
A system and method including a computer shape definition language are disclosed for defining shapes and mining time sequences that resemble the shapes. The system and method include provisions for establishing a user-defined alphabet that in turn establishes a set of elemental shapes. The system also includes simple yet powerful operators for combining the elemental shapes to define a desired time sequence shape. Moreover, intervals of actual time sequences are mapped into corresponding transition sequences using the alphabet, and the transition sequences are stored in a hierarchical index structure for easily accessing the transition sequences. The index structure is entered with the desired time sequence shape, and the index structure is traversed to identify maximal actual transition sequences which conform to the desired time sequence shape, within user-definable blurry criteria.
摘要:
A system and method including a computer shape definition language are disclosed for defining shapes and mining time sequences that resemble the shapes. The system and method include provisions for establishing a user-defined alphabet that in turn establishes a set of elemental shapes. The system also includes simple yet powerful operators for combining the elemental shapes to define a desired time sequence shape. Moreover, intervals of actual time sequences are mapped into corresponding transition sequences using the alphabet, and the transition sequences are stored in a hierarchical index structure for easily accessing the transition sequences. The index structure is entered with the desired time sequence shape, and the index structure is traversed to identify maximal actual transition sequences which conform to the desired time sequence shape, within user-definable blurry criteria.
摘要:
Techniques are provided for performing a parallel aggregation operation on data that resides in a container, such as a relational table. During generation of the execution plan for the operation, it is determined whether partition-wise aggregation should be performed, based on the grouping keys involved in the aggregation and the partition keys used to partition the container. If partition-wise aggregation is to be performed, then the assignments given to the slave processes that are assigned to scan a container are made on a partition-wise basis. The scan slaves themselves may perform full or partial aggregation (depending on whether they are the only scan slaves assigned to the partition). If the scan slaves perform no aggregation, or only partial aggregation, then the scan slaves redistribute the data items to aggregation slaves that are local to the scan slaves.
摘要:
Techniques for sharing cursors are provided. When a new query is issued, a database server determines whether the new query is semantically equivalent to a previous query. If so, then database server computes statistics associated with the new query. Based on the statistics, the database server determines whether compiling the new query would produce an execution plan that satisfies certain criteria. If so, then the cursor is used to execute the new query. In another approach, one cursor sharing technique (CST) is used to determine which cursor to use to execute a first set of semantically-equivalent queries. Statistics are gathered during execution of the first set of queries. The database server determines, based on the statistics, when to switch from using the first CST to a different CST. The different CST is used to determine which cursor to use to execute a second set of queries that are semantically-equivalent to the first set.
摘要:
Under a type of query transformation referred to herein as join factorization, the branches of an UNION/UNION ALL query that join a common table are combined to reduce accesses to the common table. The transformation can be expressed as (T1 join T2) union all (T1 join T3)=T1 join (T2 union all T3), where T1, T2 and T3 are three tables. A given query may be rewritten in many alternate ways using join factorization. Evaluating each alternative can be expensive. Therefore, the alternatives are generated and evaluated in a way that minimizes the cost of evaluating the alternatives.
摘要翻译:在这里称为连接因式分解的一种类型的查询变换中,加入公共表的UNION / UNION ALL查询的分支被组合以减少对公共表的访问。 转换可以表示为(T1连接T2)联合全部(T1连接T3)= T1连接(T2联合全T3),其中T1,T2和T3是三个表。 给定的查询可以使用连接因式分解以许多替代方式重写。 评估每个替代品可能是昂贵的。 因此,以最小化评估替代品的成本的方式生成和评估替代方案。
摘要:
A method for receiving a database query language statement and statistics information about the statement at an optimizer, and identifying an inaccurate statistic for the statement, is disclosed.
摘要:
A method of gathering performance information about a workload, and automatically identifying a set of high-load database query language statements from the workload based on the performance information, is disclosed.
摘要:
The present invention is directed to a method and mechanism for partitioning using information not directly located in the object being partitioned. According to an embodiment of the invention, foreign key-primary key relationships are utilized to create join conditions between multiple database tables to implement partitioning of a database object. Also, disclosed are methods and mechanisms to perform partition pruning.
摘要:
Approaches, techniques, and mechanisms are disclosed for maintaining a set of baseline query plans for a database command. Except in rare circumstances, a database server may only execute a command according to a baseline plan, even if the database server predicts that a different plan has a lower cost. The set of baseline plans are plans that, for one reason or another, have been determined to provide acceptable actual performance in at least one execution context. When the database server receives a request to execute a particular command, the database server, if possible, always executes the command according to the lowest predicted cost baseline plan. The database server may evolve the plan baseline to include additional plans by generating and testing new plans in response to new requests to execute the database command, or as part of a query optimization or tuning process.