公开(公告)号：WO9832064A2

公开(公告)日：1998-07-23

申请号：PCT/US9723087

申请日：1997-12-15

Applicant: TANDEM COMPUTERS INC

Inventor： CELIS PEDRO ,  VAISHNAV JAY ,  ZELLER HANSJORG

IPC: G06F17/30 ,  G06F

CPC classification number: G06F17/30463 ,  Y10S707/99932 ,  Y10S707/99933 ,  Y10S707/99934 ,  Y10S707/99935 ,  Y10S707/99936

Abstract: A system and method for optimizing a database query with improved performance enhancements is herein disclosed. The database query consists of one or more logical expressions. Through the repeated application of one or more rules, the logical expressions are transformed into physical expressions and in some cases, execution plans that implement the database query. Each expression has associated with it a set of group attributes that specifies its characteristic inputs and outputs and a cost that estimates the computational expense for executing the expression. The group attributes are used to categorize similar expressions into groups that are stored in a search data structure. They are also used to track duplicate expressions. The cost associated with an expression is used to guide the search process to consider those expressions that will produce low cost plans. The cost is estimated in accordance with a six-fold criteria with each criterion weighted to account for the context of the expression and the application's particular computing environment. The query optimizer is rule-based including transformation and implementation rules that are used to perform transformations on the logical expressions in a subproblem in order to produce a plan. A OnceGuidance guidance method is used to select a set of rules in certain cases that prevent the regeneration of an existing expression.

Abstract translation: 本文公开了一种用于优化具有改进的性能增强的数据库查询的系统和方法。 数据库查询由一个或多个逻辑表达式组成。 通过重复应用一个或多个规则，将逻辑表达式转换为物理表达式，在某些情况下，将实现数据库查询的执行计划。 每个表达式与它相关联一组指定其特征输入和输出的组属性，以及估计执行表达式的计算费用的成本。 组属性用于将类似的表达式分组到存储在搜索数据结构中的组。 它们也用于跟踪重复表达式。 与表达式相关联的成本用于指导搜索过程来考虑将生成低成本计划的表达式。 成本按照六项标准进行估算，每个标准加权以表示表达式和应用程序特定计算环境的上下文。 查询优化器是基于规则的，包括用于对子问题中的逻辑表达式执行转换以生成计划的转换和实现规则。 在一些阻止再现现有表达式的情况下，使用OnceGuidance指导方法来选择一组规则。

公开(公告)号：CA2178263A1

公开(公告)日：1996-12-08

申请号：CA2178263

申请日：1996-06-05

Applicant: TANDEM COMPUTERS INC

Inventor： ZELLER HANSJORG ,  CELIS PEDRO

IPC: G06F17/30

Abstract: A method for subquery elimination for a relational model database based on the SQL language running a database management system (DBMS) under the Tandem NonStop (tm) operating kernel. A series of seven transformation rules are applied to eliminate nested queries in the SQL language. The method and teachings of the present invention generalizes to all types of nested subqueries in SQL, allowing for more efficient computations, allocation and maintenance of system resources.

公开(公告)号：CA2167793A1

公开(公告)日：1996-07-24

申请号：CA2167793

申请日：1996-01-22

Applicant: TANDEM COMPUTERS INC

Inventor： MADRID LOUISE M ,  MEIER RICHARD A ,  PUTZOLU FRANCO ,  SHARMA SUNIL ,  O'SHEA THOMAS J ,  TROISI JAMES H ,  ZELLER HANSJORG ,  GILBERT GARY M

IPC: G06F12/00 ,  G06F17/30 ,  G06F9/45

Abstract: An SQL program executor and an SQL compiler both include options for avoiding recompilations of execution plans whenever the runtime object and the compile time object referenced by an execution plan meet predefined schema similarity criteria. Thus, recompilation is sometimes avoided even though the compile time object has been altered or the run time object is not the same object as the compile time object. To enable late binding, schema information is stored in each execution plan for each object to be accessed by the execution plan. The stored schema information is a subset of the full object schema, and includes information about all the aspects of the objects to be accessed which must remain unchanged in order for the execution plan to be operable. While executing a compiled program, the SQL executor avoids recompilations of execution plans whenever the runtime object and the compile time object referenced by an execution plan meet predefined schema similarity criteria. When a recompilation of an SQL program is required, only the execution plans which do not meet the schema similarity criteria are recompiled if the compiled program has been assigned appropriate runtime parameters. The late binding features of the SQL executor also enable a compiled program to access objects distinct from the objects referenced by the program at compile time. Similarly, the SQL compiler includes the ability to recompile only those execution plans which do not meet the schema similarity criteria and thus are inoperable.