查询优化器

此处使用了AVOIDINDEX指令，指示查询优化器不要使用函数索引。

Here , use the AVOID_INDEX directive to tell the query optimizer not to use your functional index .

针对DBMS查询优化器如何生成成本最小的查询计划问题，给出关系代数表达式的优化规则。

Aiming at how the DBMS query optimizer to generate the smallest cost query plan , optimization rules of the relational algebra expression are given .

OSCAR查询优化器的设计与实现

Design and Implementation of OSCAR Query Optimizer

本文之后主要讨论了OSCAR数据库系统查询优化器的设计和实现。

Then , this paper mainly discuss the design and implementation of OSCAR query optimization .

利用MSSqlServer2000查询优化器等工具优化SQL语句的执行性能。文中还提到优化SQL语句执行的其它技巧。

Optimize the execution performance of SQL statements by utilizing the tools like Query Optimizer of MS SQL Server 2000 . Other skills for SQL statements execution optimization are also touched upon .

另一个用途是当DB2查询优化器确定只需检查分区的一个子集来回答特定查询时，基于分区消除以提高性能。

Another purpose is to improve performance based on partition elimination when the DB2 query optimizer determines that only a subset of the partitions need to be examined to answer as particular query .

迁移到DB29的另一个好处是，混合型存储引擎和查询优化器“理解”XML，可以把涉及XML的查询映射为关系语法。

Another benefit of the move to DB29 is the hybrid storage engine and a query optimizer that " understands " XML ( mapping to relational algebra for queries involving XML ) .

如果视图可以在内部使用索引，那么可以创建一个索引规范，存储在联邦服务器上的DB2数据库系统编目中，供查询优化器使用。

If the view can use an index internally , you can create an index specification that is stored in the DB2 database system catalog on the federated server , and used by the query optimizer .

注意：查询优化器只有在表统计信息保持最新的情况下使用R-Tree索引。

Note : the query optimizer will not use the R-Tree index unless the statistics on the table are up to date .

而且，solidDB查询优化器通过以一种新的方式估计执行成本，判别内存中的表的不同性质。

Further , the solidDB query optimizer recognizes the different nature of the in-memory tables by estimating execution costs in a new way .

不管哪种模式（3NF或Star），Teradata查询优化器依赖于统计信息帮助确定最佳数据访问路径。

Regardless of schema ( 3NF or Star ), the Teradata query optimizer relies on statistics to help it determine the best way to access data .

它们仅针对字符串列进行收集，查询优化器用它们来提高“columnLIKE'%abc'”和“columnLIKE'%abc%'”类型谓词的选择性估计。

They are collected for string columns only , and they are used by the query optimizer to improve the selectivity estimates for predicates of the type " column LIKE ' % abc ' " and " column LIKE ' % abc % ' " .

理解在计划创建期间DB2fori5/OS查询优化器使用的优化目标的另一种方法是使用VisualExplain工具，该工具是iSeriesNavigator的一部分。

Another way to understand the optimization goal used by the DB2 for i5 / OS query optimizer during plan creation , is to utilize the Visual Explain tool that is part of the iSeries Navigator .

查询优化器使用数据库中的SYSSTAT目录视图来检索数据库对象的统计信息，并确定访问数据库的最佳方法。

The query optimizer uses the SYSSTAT catalog views in the database to retrieve the statistical information of the database objects and determine the best way to access the data .

这专题要求改做「近似」星型图为星型图及使用C-Store查询优化器，设计一种有效评价查询的方案。

In this project , you would devise a scheme to efficiently evaluate queries over schemas that are " near " star schemas by transforming them to star schemas and using the C-Store query optimizer .

文章详细论述了Cbase查询优化器中重写模块的设计思想与实现技术，并讨论了基于执行引擎特点引入的一组基于等价谓词的简单语句的重写规则。

In this paper , the authors first discuss the methods of realizing a query rewrite module on the basis of rewrite technology and then put forward a set of simple rewrite rules based on equivalence predicate .

最后，设计了由计划空间、方法空间和代价估计三个模块构成的星形查询优化器。

Finally , a star query optimizer has been designed .

查询优化器不会自动重新计算表的配置文件。

The query optimizer does not recalculate the profile for tables automatically .

一个并行查询优化器的设计与实现

Design and Realization of a Parallel Query Optimizer

当今通用的商业数据库的查询优化器多为基于代价的优化器。

Most of the query optimizer of current commercial DBMS is the cost-based optimizer .

选择性估计是设计空间数据库查询优化器的基础。

Selectivity Estimation is the base of the device of spatial database query optimizer .

准确的索引信息和统计信息是查询优化器中基于成本的决策的基础。

Accurate index information and statistics are fundamental to cost-based decisions in the query optimizer .

这些视图包括一些包含对查询优化器有用的统计信息的列。

These views include columns containing statistical information that is useful to the query optimizer .

查询优化器是数据库系统最重要的组件之一。

The query optimizer is one of the most important components of a database system .

如果没有设计良好的查询优化器，即使是小型的数据库也会表现出非常明显的性能低下。

Without a favourable query optimizer , even if a minitype database behaves remarkable low performance .

清楚所有适用的远程索引有助于联邦查询优化器生成更好的执行计划。

Awareness of all applicable remote indexes can help the federated query optimizer generate better execution plans .

查询优化器的面向对象框架

Object-Oriented Framework for Query Optimizer

表明不存在可能对查询优化器有用的列统计。

Indicates that column statistics which would have been useful to the query optimizer are not present .

DB2UDB中包含了一个功能强大基于成本的查询优化器，用于确定访问数据的最佳策略。

DB2 UDB comes with a powerful cost-based query optimizer that determines the best strategy to access data .

查询优化器必须分析可能的计划并选择一个预计成本最低的计划。

The query optimizer must analyze the possible plans and choose the one with the lowest estimated cost .