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    • 3. 发明授权
    • Redundant join elimination and sub-query elimination using subsumption
    • 使用包含冗余加入消除和子查询消除
    • US07587383B2
    • 2009-09-08
    • US10377896
    • 2003-02-27
    • Fred KooTing Y. Leung
    • Fred KooTing Y. Leung
    • G06F7/00G06F17/30
    • G06F17/30454G06F17/30451Y10S707/99932Y10S707/99933Y10S707/99934
    • A method, computer readable medium, and system for optimizing a query in a relational database processing system is disclosed. The present invention relates to a query rewrite optimization method for eliminating a redundant join and equivalent subquery in an SQL query before generation and selection of the optimal query execution plan. The method of the present invention includes evaluating the query to identify a join predicate joining a sub-expression of the query to itself, and determining whether a row set producible from a first set of references of the query to the sub-expression is subsumed by a row set producible from a second set of references of the query to the sub-expression. Based on such evaluation and determination, the query may be reformed to eliminate the join predicate and the second quantifier. A further determination of the removability of the second quantifier may be required such as by evaluating a cardinality constraint when query output cardinality is material.
    • 公开了一种在关系数据库处理系统中优化查询的方法,计算机可读介质和系统。 本发明涉及在生成和选择最优查询执行计划之前消除SQL查询中的冗余连接和等效子查询的查询重写优化方法。 本发明的方法包括评估查询以识别将查询的子表达式连接到其自身的连接谓词,以及确定从第一组查询引用到子表达式的行集合是否被 一组可从查询的第二组引用生成的子集。 基于这样的评估和确定,可以改进查询以消除连接谓词和第二定量。 可能需要进一步确定第二量词的可移除性,例如当查询输出基数是重要的时通过评估基数约束。
    • 6. 发明授权
    • Efficient implementation of an index structure for multi-column bi-directional searches
    • 高效实施多列双向搜索的索引结构
    • US06965894B2
    • 2005-11-15
    • US10104684
    • 2002-03-22
    • Ting Y. LeungKar Ming TangThanh Tan Pham
    • Ting Y. LeungKar Ming TangThanh Tan Pham
    • G06F17/30
    • G06F17/30327Y10S707/99933
    • An index structure for use by a database management system comprises a variant of a Patricia tree, wherein each node stores a column value that identifies a specified column of the constructed n-column search key that is used to determine a next path taken through the tree, a null value N that specifies whether a null value or an actual data value of the specified column of the constructed n-column search key is used to determine the next path taken through the tree, and a position value that specifies a portion of the specified column from the constructed n-column search key to be used to determine the next path taken through the tree when the actual data value of the specified column of the constructed n-column search key is used to determine the next path taken through the tree.
    • 由数据库管理系统使用的索引结构包括Patricia树的变体,其中每个节点存储列值,该列标识用于确定通过该树取得的下一路径的构造的n列搜索关键字的指定列 指定空值N,其指定构造的n列搜索关键字的指定列的空值或实际数据值是否用于确定通过树取得的下一个路径,以及位置值,其指定 指定的列从构造的n列搜索关键字用于确定通过树获取的下一个路径,当构造的n列搜索关键字的指定列的实际数据值用于确定通过树获取的下一个路径 。
    • 8. 发明授权
    • Optimization of SQL queries using early-out join transformations of
column-bound relational tables
    • 使用列关联表的早期连接变换优化SQL查询
    • US5548758A
    • 1996-08-20
    • US463968
    • 1995-06-05
    • Mir H. PiraheshTing Y. LeungGuy M. LohmanEugene J. ShekitaDavid E. Simmen
    • Mir H. PiraheshTing Y. LeungGuy M. LohmanEugene J. ShekitaDavid E. Simmen
    • G06F17/30
    • G06F17/30454Y10S707/99932Y10S707/99935
    • A method and apparatus for optimizing SQL queries in a relational database management system uses early-out join transformations. An early-out join comprises a many-to-one existential join, wherein the join scans an inner table for a match for each row of the outer table and terminates the scan for each row of the outer table when a single match is found in the inner table. To transform a many-to-many join to an early-out join, the query must include a requirement for distinctiveness, either explicitly or implicitly, in one or more result columns for the join operation. Distinctiveness can be specified using the DISTINCT keyword in the SELECT clause or can be implied from the predicates present in the query. The early-out join transformation also requires that no columns of the inner table be referenced after the join, or if an inner table column is referenced after the join, that each referenced column be "bound". A referenced column can be bound in one of three ways: (1) an inner table column can be bound to a constant through an equality predicate, (2) an inner table column can be bound to an outer table column, or (3) an inner table column can be bound to a correlated value, wherein the correlated value originates outside the query block. In all three cases, an inner table column can be bound through the transitivity of equality predicates.
    • 用于优化关系数据库管理系统中的SQL查询的方法和装置使用早期连接变换。 早期连接包括多对一存在连接,其中,连接扫描内部表以获取外部表的每一行的匹配,并且当找到单个匹配时终止外部表的每一行的扫描 内表。 要将多对多连接转换为早期连接,查询必须在连接操作的一个或多个结果列中明确或隐式地包含独特性的要求。 可以使用SELECT子句中的DISTINCT关键字指定不同之处,也可以从查询中存在的谓词中暗示。 早期连接转换还要求在连接之后不引用内部列的列,或者如果在连接之后引用了内部列列,则每个引用的列都将被“绑定”。 引用的列可以通过三种方式之一来绑定:(1)内表列可以通过相等谓词绑定到常量,(2)内表列可绑定到外表列,或(3) 可以将内表列绑定到相关值,其中相关值起始于查询块之外。 在所有三种情况下,内表列可以通过相等谓词的传递性来约束。
    • 10. 发明授权
    • Optimization of SQL queries using early-out join transformations
    • 使用Early-out连接变换优化SQL查询
    • US5548754A
    • 1996-08-20
    • US385177
    • 1995-02-07
    • Mir H. PiraheshTing Y. LeungGuy M. LohmanEugene J. ShekitaDavid E. Simmen
    • Mir H. PiraheshTing Y. LeungGuy M. LohmanEugene J. ShekitaDavid E. Simmen
    • G06F17/30
    • G06F17/30454Y10S707/99932Y10S707/99935
    • A method and apparatus for optimizing SQL queries in a relational database management system uses early-out join transformations. An early-out join comprises a many-to-one existential join, wherein the join scans an inner table for a match for each row of the outer table and terminates the scan for each row of the outer table when a single match is found in the inner table. To transform a many-to-many join to an early-out join, the query must include a requirement for distinctiveness, either explicitly or implicitly, in one or more result columns for the join operation. Distinctiveness can be specified using the DISTINCT keyword in the SELECT clause or can be implied from the predicates present in the query. The early-out join transformation also requires that no columns of the inner table be referenced after the join, or if an inner table column is referenced after the join, that each referenced column be "bound". A referenced column can be bound in one of three ways: (1) an inner table column can be bound to a constant through an equality predicate, (2) an inner table column can be bound to an outer table column, or (3) an inner table column can be bound to a correlated value, wherein the correlated value originates outside the query block. In all three cases, an inner table column can be bound through the transitivity of equality predicates.
    • 用于优化关系数据库管理系统中的SQL查询的方法和装置使用早期连接变换。 早期连接包括多对一存在连接,其中,连接扫描内部表以获取外部表的每一行的匹配,并且当找到单个匹配时终止外部表的每一行的扫描 内表。 要将多对多连接转换为早期连接,查询必须在连接操作的一个或多个结果列中明确或隐式地包含独特性的要求。 可以使用SELECT子句中的DISTINCT关键字指定不同之处,也可以从查询中存在的谓词中暗示。 早期连接转换还要求在连接之后不引用内部列的列,或者如果在连接之后引用了内部列列,则每个引用的列都将被“绑定”。 引用的列可以通过三种方式之一来绑定:(1)内表列可以通过相等谓词绑定到常量,(2)内表列可绑定到外表列,或(3) 可以将内表列绑定到相关值,其中相关值起始于查询块之外。 在所有三种情况下,内表列可以通过相等谓词的传递性来约束。