熊猫的非唯一索引对性能有什么影响?。
What is the performance impact of non-unique indexes in pandas?
表的主键和所有惟一索引都必须是相关分区键的超集。
The primary key and any unique index of the table must be a superset of the associated partitioning key.
索引idx6还是与查询6中的谓词相匹配的惟一索引。
Index idx6 is also the only index that matches the predicate in query 6.
显然这并不像使用一个单一索引的有序列表那样简单，但是它可以做到。
Obviously, this is not as trivial as using a single index's ordered list, but it can be done.
定义惟一索引的索引规范还将关于索引列惟一性的信息传递给联邦系统。
An index specification that defines a unique index also conveys information about the uniqueness of the index columns to the federated system.
然而，DB 2复制要求使用一个主键或惟一索引来区分一个表中的记录。
However, DB2 replication requires a key or index to uniquely identify rows in a table.
换句话说，作为分区键一部分的所有列都必须出现在主键或惟一索引定义中。
In other words, all columns that are part of the partitioning key must be present in the primary key or unique index definition.
因为其是一个唯一索引扫描，所以在访问路径图中不显示FETCH或表节点。
There is no FETCH or table node shown in the access path graph because it is an index-only scan.
原表需要一个主键或则唯一索引，因为删除的触发器需要，否则数据不会被复制。
The new table 'test'. '_online_table_new' does not have a PRIMARY KEY or a unique index which is required for the DELETE trigger.
ccd表中必须有惟一性约束——可以通过主键或者源表或ccd表上的惟一索引实现。
Uniqueness in the CCD table must be enforced — either by a primary key or unique index on the source table or CCD table.
此外，在DB 2中创建复制之前，您会希望保证每一个数据库表都具有一个主键或惟一索引。
Also, before setting up replication in DB2, you will want to ensure that every database table has a primary key or unique index.
如果一个以上的资料列中的某单一资料行为NULL，您将无法建立该单一资料行的唯一索引。
You cannot create a unique index on a single column if that column contains NULL in more than one row.
与RDBMS索引相似，可以使用多个属性创建复合索引，也可创建唯一索引，确保不存在重复的值。
Like RDBMS indexes, you can create compound indexes using multiple attributes, and unique indexes, which ensure that duplicate values are not allowed.
同样地，如果一个以上的资料列中的一组资料行全为NULL的话，您将无法在该组资料行上建立唯一索引。
Similarly, you cannot create a unique index on multiple columns if the combination of columns contains NULL in more than one row.
从性能的角度来看，这被认为是一个非常有效的联接操作，因为通过贯穿唯一索引的唯一访问扫描内部表的成本是最优的。
From the performance perspective, this is considered a very efficient join operation, because the cost for scanning the inner table is optimal via unique access through a unique index.
通常情况下，在基础索引提供好处(如唯一索引访问、避免排序或一些类似的好处)时，可通过优化器选择非匹配索引扫描。
Typically, a non-matching index scan is chosen by the optimizer when the underlying index provides benefits such as index-only access, avoids sort, or some similar benefit.
大多数关键字都有一个索引，显示词汇项及其相关术语是如何组织的。
Most keywords have an index that shows how lexical items and their related terms are organized.
这个脚本将会提示您要么删除现存的索引，要么创建一个新的索引。
This script will prompt you to either delete the existing index or create a new index.
谷歌的搜索引擎在全球如此流行，以至于搜索变成了谷歌，而谷歌也变成了一个动词。
Google's search engine is so widespread across the world that search became Google, and google became a verb.
她查了一下索引，之后翻到关于早期加州中国移民的那一页。
She checked the index and turned over to a page about early Chinese immigrants in California.
关于这本书，搜索引擎只是给了我一些简短的介绍，而没有给出全部内容。
The search engine just gave me some brief introduction rather than the whole content of the book.
这意味着，当你搜索“美洲虎”，搜索引擎会知道你要找一辆车还是一只大猫。
What this means is that the search engine will know whether you are looking for a car or a big cat when you search for "jaguar".
1996年，佩奇在斯坦福大学发起了一个学术项目，该项目最终成为了谷歌的搜索引擎。
It was Page who, at Stanford in 1996, initiated the academic project that eventually became Google's search engine.
格兰德的思维方式就像互联网搜索引擎一样，能生成用户正在搜索的物体的数十张图像。
Grand's mind works like the Internet search engine which produces dozens of images of an object a user is searching for.
如果该字符完成了一个单词，编辑程序决定是否将该词添加到索引中。
If the character completes a word, the editor determines whether that word should be added to the index.
谷歌正在开发微博客搜索引擎这一说法的证据并不确凿。
This is not proof-positive that Google is developing a microblogging search engine.
解码器必须创建一个认知空间，在该认知空间中可以通过索引来实现专门的元素和术语。
The decoder has to create a cognitive space in which the deictic elements and terms can be realized indexically.
这个参数决定了一个索引块中的最大的文档数。
This parameter determines the maximum number of documents per segment index.
如果动作是一个索引，那么它常常采用对应字段的数据类型。
If this is an index, it usually takes on the data type of the corresponding field.
通过将第一个索引与图4中所建议的索引进行比较，我们认识到，它是已有索引中某一个索引的子集。
By comparing the first index to the recommended ones in Figure 4, we realize that it is a subset of one of the existing indexes.
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