优化器何时可以选择星型连接计划。
介绍星型连接计划的解释输出。
星型连接计划利用下推散列连接技术。
星型连接也支持雪花模式。
星型连接计划的性能优势。
促进或阻止星型连接优化。
本文还介绍了星型连接在解释输出中是如何表示的。
It also shows how star join is represented in explain output.
网络系统采用以太组网方案，为星型连接拓扑结构设计。
The computer network subsystem is designed ethernet which is star connection structure.
如果查询中使用星型连接指令，指令会将会话环境设置覆盖。
If star join directives are used in a query, directives override session environment setting.
模式不需要明确指定一列是主键或唯一键来产生星型连接计划。
The schema does not need to specify explicitly that a column is a primary or unique key to produce a star join plan.
所有新的星型连接指令都是查询层次的指令，会影响查询的执行。
All the new star join directives are query level directives that affect the execution of a query.
当使用“强制”选项时，当前会话的所有查询只要可能就使用星型连接计划。
When the "forced" option is used, star join plans will be favored whenever possible for all queries in current session.
FACT (table)—FACT指令指定在星型连接优化中使用的事实表。
Fact (table) - The fact directive specifies a fact table to be used during star join optimization.
在设计的双层光互连网络中，上层网络是星型连接，依靠数字路由结点进行通信。
A two-layer parallel optical interconnection network has been designed. The top layer was a star network, which was made up of digital routing nod, node computer and optical network interface CARDS.
STAR_JOIN—STAR_JOIN指令指示优化器尽可能地选择星型连接计划。
STAR_JOIN - the STAR_JOIN directive instructs the optimizer to favor a star join plan whenever possible.
只有查询中包含满足以下要求的星型或雪花模式的表时，优化器才可以选择星型连接计划。
The optimizer can choose a star join plan only if a query involves tables from a star or snowflake schema that meets the following requirements.
我们使用前面的同一个示例查询来说明如何解释星型连接计划的SETEXPLAIN输出。
To show how to interpret SET EXPLAIN output for star join plans, we use the same example query as before.
一个星型连接查询通常包含一个事实表和几个维度表，事实表和每个维度表之间都有连接谓词。
A star join query typically involves a fact table and several dimension tables, with join predicates between the fact table and each dimension table.
星型连接计划中，数据库服务器在维度表中构建散列表的同时从维度表中下推键来过滤事实表。
In a star join plan, the database server pushes down keys from a dimension table to filter the fact table at the same time as it builds the hash table on the dimension table.
新的优化器指令和会话环境控制因为影响优化器对星型连接优化的考虑，所以文中也包含了它们的介绍。
New optimizer directives and session environment controls are also introduced for influencing optimizer consideration of star join optimization.
不选用双绞线，是极端过错的。485总线一定要是手牵手式的总线结构，坚决根绝星型连接和分叉连接。
Do not use twisted pair, is extremely wrong. 485 bus must be hand in hand type bus structure, resolutely eradicate star connection and branch connection.
利用下推连接技术的星型连接计划使得散列连接更加有效的主要原因是，在初期减少了事实表(探测表)的行数。
A star join plan utilizing push-down hash join technology makes hash joins more effective primarily due to reduction of fact table (probe table) rows early on.
为了实现星型连接查询的最佳执行计划，优化器在适当的时候会考虑星型连接优化，并根据成本因素来决定星型连接计划。
The optimizer considers star join optimization when appropriate and decides on star join plan based on cost considerations in order to come up with best execution plan for a star join query.
也引入了新的SETOPTIMIZATIONENVIRONMENT选项，用于影响优化器对星型连接计划的考虑。
New SET OPTIMIZATION ENVIRONMENT options are also introduced for influencing optimizer consideration of star join plans.
在您看到星型连接优化的优点后，本文通过带有注释的解释输出准确地告诉您星型连接计划的信息是如何出现在解释文件中的。
After you see the advantages of star join optimization, this article provides annotated explain output to show you precisely how star join plan information appears in explain file.
SETOPTIMIZATION ENVIRONMENT star_join语句可用来启用、禁用或强制星型连接计划用于当前会话的所有查询。
The SET OPTIMIZATION ENVIRONMENT STAR_JOIN statement can be used to enable, disable, or force star join plans for all queries in the current session.
SETOPTIMIZATIONENVIRONMENTFACT语句针对当前会话的所有查询，用于指定一个在星型连接优化中可被视为事实表的表清单。
The SET OPTIMIZATION ENVIRONMENT FACT statement can be used to specify a list of tables that can be considered as fact tables during star join optimization for all queries in the current session.
系统的布局采用星型拓扑模式，一个监控计算机可以连接多台数据分站，一个分站可以连接多种类型的传感器。
System adopts starriness patter, and a computer can connect some subsystems of signal acquisition, and a subsystem of signal acquisition can connect different type sensors.
PACS服务器采用星型拓扑结构与各设备连接，图像浏览终端通过交换机采用总线结构与PACS服务器连接。
Image display workstations have been connected to the PACS server by a bus topology through switch equipments.
PACS服务器采用星型拓扑结构与各设备连接，图像浏览终端通过交换机采用总线结构与PACS服务器连接。
Image display workstations have been connected to the PACS server by a bus topology through switch equipments.
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