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.
查询优化器将尝试减少发送到数据源的消息的数量。
The query optimizer will try to reduce the number of messages sent to the data source.
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.
按照查询优化器建议的键创建逻辑文件能够执行得更快。
Can perform faster with the creation of a keyed logical file containing the keys suggested by 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.
查询优化器根据从每个表检索的行数估计查询成本。
The query optimizer bases query-cost estimates on the number of rows to be retrieved from each table.
通常，查询优化器选择将在最短时间内返回整个结果集的计划。
In general, the query optimizer selects a plan that will return the entire result set in the shortest amount of time.
有了这个特性，查询优化器可以在决定访问计划时立即考虑索引。
With this feature, the query optimizer can immediately consider the index when determining an access plan.
如果网络较慢，查询优化器还尝试减少发送到数据源的消息数量。
The query optimizer also tries to reduce the number of messages sent to the data source if the network is slow.
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.
下推的决定是包装器在计划阶段与查询优化器一起做出的。
The push-down decision is made by the wrapper during the planning phase, while working with the query optimizer.
查询优化器的一项新特性支持一种新的索引扫描，即索引自连接路径。
A new feature of the query optimizer supports a new type of index scan, called an index self-join path.
在为查询生成计划的过程中，查询优化器与非关系包装器通信。
During plan generation for the query, the query optimizer communicates with the non-relational wrapper.
此类操作(由恰当的关系理论作为支持)是数据库查询优化器的核心所在。
Manipulations like this (backed by the proper relational theory) are at the heart of database query optimizers. The resulting tree is shown in Figure 2.
如果有了准确的统计信息，那么查询优化器一般能够得出正确的选择性估计。
Given accurate statistics, the query optimizer generally comes up with correct selectivity estimates.
一个条目被添加到系统编目中，以向查询优化器表明存在那样的一个远程索引。
An entry is added to the system catalog to indicate to the query optimizer that such a remote index exists.
并行查询优化器的目标是缩减庞大的计划搜索空间，获得优化的查询规划。
The key problem is how to prune the big search space in order to get an optimized query plan for query parallel optimization.
SQL解释工具提供查询优化器为 SQL语句所选择的访问计划的有关详细信息。
The SQL explain facility provides detailed information about the access plan that the query optimizer chooses for an SQL statement.
VisualExplain还包括关于查询优化器所考虑和选择的数据库对象的信息。
Visual Explain also includes information on the database objects considered and chosen by the query optimizer.
查询功能是产品的一个便捷特性，但它不受高端数据库中所有高级查询优化器的支持。
The query functionality is a valid convenience feature of the product, but it is not backed by all the sophisticated query optimizers found in top-end databases.
DB 2 UDb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.
这使得查询优化器可以更有效地分析复杂的查询，因为现在统计信息近似地反映实际成本。
This allows the query optimizer to do a better job of analyzing the complex query, as the statistics can now closely reflect the actual cost.
为特定类型的复杂数据调整万能服务器的查询优化器，能大大提高这些数据类型的查询速度。
Tuning the Universal Server's query optimizer for particular types of complex data can vastly improve querying speed on those data types.
第4步：我们需要对查询进行explain(解释)，以查看DB 2查询优化器所选择的访问计划。
STEP d: We need to explain the queries to view the access plans chosen by the DB2 query optimizer.
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.
在select语句中使用视图，可以限制表的连接顺序，同时也限制查询优化器在考虑访问计划时的选择。
Using views in a SELECT statement can restrict the join order of the tables and limit the query optimizer's choices when considering access plans.
当设置了该选项时，查询优化器选择按照PDA的指示将大部分工作下推到数据源的查询执行计划。
When this option is set, the query optimizer chooses the query execution plan that pushes the most work down to the data source as indicated by the PDA component.
注意：当索引表达式被用于关系表达式，或作为某个操作符类函数的参数时，查询优化器将考虑使用函数索引。
Note: the query optimizer considers using a functional index when the index expression is used in a relational expression or as an argument to one of the operator class functions.
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.
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.
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