Introduction to MongoDB¶
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MongoDB is an open-source document database that provides high performance, high availability, and automatic scaling.
Document Database¶
A record in MongoDB is a document, which is a data structure composed of field and value pairs. MongoDB documents are similar to JSON objects. The values of fields may include other documents, arrays, and arrays of documents.
The advantages of using documents are:
- Documents (i.e. objects) correspond to native data types in many programming languages.
- Embedded documents and arrays reduce need for expensive joins.
- Dynamic schema supports fluent polymorphism.
Key Features¶
High Performance¶
MongoDB provides high performance data persistence. In particular,
- 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.
Rich Query Language¶
MongoDB supports a rich query language to support read and write operations as well as:
High Availability¶
MongoDB’s replication facility, called replica set, provides:
- automatic failover and
- data redundancy.
A replica set is a group of MongoDB servers that maintain the same data set, providing redundancy and increasing data availability.
Horizontal Scalability¶
MongoDB provides horizontal scalability as part of its core functionality:
- Sharding distributes data across a cluster of machines.
- Tag aware sharding allows for directing data to specific shards, such as to take into consideration geographic distribution of the shards.
Support for Multiple Storage Engines¶
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.