|
|
@@ -1,61 +1,43 @@
|
|
|
[[relations]]
|
|
|
-== Handling Relationships
|
|
|
+== 关联关系处理
|
|
|
|
|
|
-In the real world, relationships((("relationships"))) matter: blog posts have comments, bank
|
|
|
-accounts have transactions, customers have bank accounts, orders have order
|
|
|
-lines, and directories have files and subdirectories.
|
|
|
+现实世界有很多重要的关联关系((("relationships")))：博客帖子有一些评论，银行账户有多次交易记录，客户有多个银行账户，订单有多个订单明细，文件目录有多个文件和子目录。
|
|
|
|
|
|
-Relational databases are specifically designed--and this will not come as a
|
|
|
-surprise to you--to manage((("relational databases", "managing relationships"))) relationships:
|
|
|
+关系型数据库被明确设计--毫不意外--用来进行关联关系管理((("relational databases", "managing relationships")))：
|
|
|
|
|
|
-* Each entity (or _row_, in the relational world) can be uniquely identified
|
|
|
- by a _primary key_.((("primary key")))
|
|
|
+* 每个实体（或 _行_ ，在关系世界中）可以被 _主键_ 唯一标识。((("primary key")))
|
|
|
|
|
|
-* Entities are _normalized_. The data for a unique entity is stored only
|
|
|
- once, and related entities store just its primary key. Changing the data of
|
|
|
- an entity has to happen in only one place.((("joins", "in relational databases")))
|
|
|
+* 实体 _规范化_ （范式）。唯一实体的数据只存储一次，而相关实体只存储它的主键。只能在一个具体位置修改这个实体的数据。((("joins", "in relational databases")))
|
|
|
|
|
|
-* Entities can be joined at query time, allowing for cross-entity search.
|
|
|
+* 实体可以进行关联查询，可以跨实体搜索。
|
|
|
|
|
|
-* Changes to a single entity are _atomic_, _consistent_, _isolated_, and
|
|
|
- _durable_. (See http://en.wikipedia.org/wiki/ACID_transactions[_ACID Transactions_]
|
|
|
- for more on this subject.)
|
|
|
+* 单个实体的变化是 _原子的_ ， _一致的_ ， _隔离的_ ， 和
|
|
|
+ _持久的_ 。 （可以在 http://en.wikipedia.org/wiki/ACID_transactions[_ACID Transactions_]
|
|
|
+ 中查看更多细节。）
|
|
|
|
|
|
-* Most relational databases support ACID transactions across multiple
|
|
|
- entities.
|
|
|
+* 大多数关系数据库支持跨多个实体的 ACID 事务。
|
|
|
|
|
|
-But relational ((("ACID transactions")))databases do have their limitations, besides their poor support
|
|
|
-for full-text search. Joining entities at query time is expensive--the more
|
|
|
-joins that are required, the more expensive the query. Performing joins
|
|
|
-between entities that live on different hardware is so expensive that it is
|
|
|
-just not practical. This places a limit on the amount of data that can be
|
|
|
-stored on a single server.
|
|
|
+但是关系型数据库((("ACID transactions")))有其局限性，包括对全文检索有限的支持能力。
|
|
|
+实体关联查询时间消耗是很昂贵的，关联的越多，消耗就越昂贵。特别是跨服务器进行实体关联时成本极其昂贵，基本不可用。
|
|
|
+但单个的服务器上又存在数据量的限制。
|
|
|
|
|
|
-Elasticsearch, like((("NoSQL databases"))) most NoSQL databases, treats the world as though it were
|
|
|
-flat. An index is a flat collection of independent documents.((("indices"))) A single
|
|
|
-document should contain all of the information that is required to decide
|
|
|
-whether it matches a search request.
|
|
|
+Elasticsearch ，和大多数 NoSQL 数据库类似，是扁平化的。索引是独立文档的集合体。
|
|
|
+((("indices"))) 文档是否匹配搜索请求取决于它是否包含所有的所需信息。
|
|
|
|
|
|
-While changing the data of a single document in Elasticsearch is
|
|
|
-http://en.wikipedia.org/wiki/ACID_transactions[ACIDic], transactions
|
|
|
-involving multiple documents are not. There is no way to roll back the index
|
|
|
-to its previous state if part of a transaction fails.
|
|
|
+Elasticsearch 中单个文档的数据变更是 http://en.wikipedia.org/wiki/ACID_transactions[ACIDic] 的，
|
|
|
+而涉及多个文档的事务则不是。当一个事务部分失败时，无法回滚索引数据到前一个状态。
|
|
|
|
|
|
-This FlatWorld has its advantages:
|
|
|
+扁平化有以下优势：
|
|
|
|
|
|
-* Indexing is fast and lock-free.
|
|
|
-* Searching is fast and lock-free.
|
|
|
-* Massive amounts of data can be spread across multiple nodes, because each
|
|
|
- document is independent of the others.
|
|
|
+* 索引过程是快速和无锁的。
|
|
|
+* 搜索过程是快速和无锁的。
|
|
|
+* 因为每个文档相互都是独立的，大规模数据可以在多个节点上进行分布。
|
|
|
|
|
|
-But relationships matter. Somehow, we need to bridge the gap between
|
|
|
-FlatWorld and the real world.((("relationships", "techniques for managing relational data in Elasticsearch"))) Four common techniques are used to manage
|
|
|
-relational data in Elasticsearch:
|
|
|
+但关联关系仍然非常重要。某些时候，我们需要缩小扁平化和现实世界关系模型的差异。((("relationships", "techniques for managing relational data in Elasticsearch")))以下四种常用的方法，用来在 Elasticsearch 中进行关系型数据的管理：
|
|
|
|
|
|
* <<application-joins,Application-side joins>>
|
|
|
* <<denormalization,Data denormalization>>
|
|
|
* <<nested-objects,Nested objects>>
|
|
|
* <<parent-child,Parent/child relationships>>
|
|
|
|
|
|
-Often the final solution will require a mixture of a few of these techniques.
|
|
|
-
|
|
|
+通常都需要结合其中的某几个方法来得到最终的解决方案。
|
luotitan