MongoDB简介¶
MongoDB is an open-source document database that provides high performance, high availability, and automatic scaling.
文档数据库¶
MongoDB中的一条记录就是一个文档，是一个数据结构，由字段和值对组成。MongoDB文档与JSON对象类似。字段的值有可能包括其它文档、数组以及文档数组。
使用文档的优势在于：
- Documents (i.e. objects) correspond to native data types in many programming languages.
嵌入文档及数组减少了昂贵的joins操作的需求。
动态的设计模式支持流畅的多态。
主要特征¶
高性能¶
MongoDB提供高性能的数据持久化。特别是，
- Support for embedded data models reduces I/O activity on database system.
- Indexes support faster queries and can include keys from embedded documents and arrays.
丰富的查询语言¶
MongoDB supports a rich query language to support read and write operations (CRUD) as well as:
- Data Aggregation
:query:` 文本检索 <$text>` 以及 :doc:` 地理空间查询 </tutorial/geospatial-tutorial>` 。
高可用性¶
MongoDB的复制设施，也叫作 :ref:` 复制集 <replication-introduction>` 提供了：
自动的 故障恢复以及
数据冗余。
A replica set is a group of MongoDB servers that maintain the same data set, providing redundancy and increasing data availability.
水平扩展能力¶
MongoDB provides horizontal scalability as part of its core functionality:
- Sharding distributes data across a cluster of machines.
Tag aware 分片运行直接将数据引导到特定的分片，例如，考虑分片的地理分布等，
多个存储引擎的支持¶
MongoDB supports multiple storage engines, such as:
In addition, MongoDB provides pluggable storage engine API that allows third parties to develop storage engines for MongoDB.