Introduction
MongoDB is a popular NoSQL database that uses a document-oriented data model. Unlike traditional relational databases, MongoDB does not use tables, rows, or columns to store data. Instead, it uses collections of documents, which are similar to JSON objects.
MongoDB was developed by MongoDB Inc. and released in 2009. It is written in C++ and is available under the Apache License 2.0.
Document-oriented data model
In MongoDB, data is stored in collections, which are similar to tables in relational databases. However, unlike tables, collections do not enforce a fixed schema. Each document in a collection can have its own set of fields and data types, making MongoDB highly flexible.
Documents in MongoDB are stored in BSON format, which is a binary representation of JSON. BSON allows for efficient storage and retrieval of data, and also supports additional data types such as binary data and date/time values.
Query language
MongoDB provides a rich query language for searching and manipulating data. The query language is based on JavaScript syntax and allows for complex queries to be constructed using a combination of operators and functions.
MongoDB queries can be executed using the find()
method, which returns a cursor to the matching documents. Cursors allow for efficient processing of large result sets, as they only load a subset of the results into memory at a time.
Indexing
MongoDB supports indexing of collections to improve query performance. Indexes can be created on individual fields, as well as on combinations of fields. Indexes can also be created as unique or sparse, depending on the requirements of the application.
MongoDB uses a B-tree index structure to efficiently retrieve matching documents. B-tree indexes allow for efficient range queries, as well as equality and inequality queries.
Scaling
MongoDB is designed to scale horizontally, meaning that it can be distributed across multiple servers to handle large amounts of data and traffic. MongoDB provides several options for scaling, including sharding and replica sets.
Sharding involves partitioning a collection across multiple servers, or shards. Each shard holds a subset of the data, allowing for efficient distribution and parallel processing of queries. MongoDB provides automatic balancing of data across shards, as well as support for sharding key selection and routing.
Replica sets involve maintaining multiple copies of the data on different servers, or nodes. Each replica set consists of a primary node and one or more secondary nodes. The primary node handles all write operations, while the secondary nodes maintain a copy of the data and handle read operations. MongoDB provides automatic failover and promotion of secondary nodes to primary, as well as support for read preference selection.
Conclusion
MongoDB is a popular NoSQL database that provides a document-oriented data model, rich query language, indexing, and scaling options. Its flexible schema and powerful query language make it a popular choice for a wide range of applications, including web, mobile, and IoT.
While MongoDB has some trade-offs compared to traditional relational databases, such as less strict data consistency and less mature tooling around schema migrations, its many benefits make it an attractive choice for modern applications that require flexibility, scalability, and agility.
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