- MongoDB is developed by MongoDB Inc., It is a free and open-source cross-platform document-oriented database program, Classified as a NoSQL database program.
- MongoDB uses JSON-like documents with dynamic schemas which helps in creating records without first defining the structure, such as the fields or the types of their values.
- Instead of storing data in tables made of individual rows as a Relational Database does, MongoDB stores the data in collections made out of individual documents in a binary representation called BSON or Binary JSON.
- Related information is stored together for fast query access through the MongoDB query language.
Advantages of MongoDB over RDBMS
a.)Schema less :MongoDB is a document database in which one collection holds different documents. Number of fields, content and size of the document can differ from one document to another.
b.)Structure of a single object is clear.
c.)No complex joins.
d.)Deep query-ability. MongoDB supports dynamic queries on documents using a document-based query language that’s nearly as powerful as SQL.
f.) MongoDB is easy to scale.
g.)Conversion/mapping of application objects to database objects not needed.
h.)Uses internal memory for storing the (windowed) working set, enabling faster access of data.
Ad hoc queries
Fields in a MongoDB document can be indexed with primary and secondary indices.
MongoDB provides high availability with replica sets.A replica set consists of two or more copies of the data. Each replica set member may act in the role of primary or secondary replica at any time. All writes and reads are done on the primary replica by default. Secondary replicas maintain a copy of the data of the primary using built-in replication. When a primary replica fails, the replica set automatically conducts an election process to determine which secondary should become the primary. Secondaries can optionally serve read operations, but that data is only eventually consistent by default.
MongoDB scales horizontally using sharding. The user chooses a shard key, which determines how the data in a collection will be distributed. The data is split into ranges based on the shard key and distributed across multiple shards. Alternatively, the shard key can be hashed to map to a shard – enabling an even data distribution.
MongoDB can run over multiple servers, balancing the load or duplicating data to keep the system up and running in case of hardware failure.
MongoDB can be used as a file system with load balancing and data replication features over multiple machines for storing files.This function, called grid file system, is included with MongoDB drivers. MongoDB exposes functions for file manipulation and content to developers. GridFS divides a file into parts, or chunks, and stores each of those chunks as a separate document.
MapReduce can be used for batch processing of data and aggregation operations.The aggregation framework enables users to obtain the kind of results for which the SQL GROUP BY clause is used. Aggregation operators can be strung together to form a pipeline – analogous to Unix pipes. The aggregation framework includes the $lookup operator which can join documents from multiple documents, as well as statistical operators such as standard deviation.
MongoDB supports fixed-size collections called capped collections. This type of collection maintains insertion order and, once the specified size has been reached, behaves like a circular queue.