7.1. General information about MongoDB

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MongoDB is a document—oriented database management system that does not require a description of the table schema.

Basic concepts

Database. Shared storage that contains collections of documents. An important feature is that the database does not physically exist until there is any data in it.

Collection. A set of documents, analogous to a table in MySQL. Unlike a table, one collection can contain documents with different structures, sizes, values, and relationships.

Document. A BSON file with data in the form of keys and their values, analogous to a row in a MySQL table. Unlike a string, a document can store information with a complex structure and is more flexible.

Field. One record in a document is a key that corresponds to a certain set of data, analogous to a column in a MySQL table.

_id. An identifier required for each document, similar to the primary key in a MySQL table. Helps to access data and serves to distinguish records from each other. Created automatically if not explicitly set when creating a new document.

Versions

Available versions of MongoDB:

  • 4.2
  • 4.4
  • 5.0
  • 6.0

Version selectable only at the stage order and does not change thereafter.

Plans

Available rates vary:

  • The number of processor cores available.
  • The amount of RAM.
  • The amount of disk space.

In the process of using MongoDB tariff can be changed.

Databases

Can create any quantity databases, as many as the disk space of the selected tariff allows.

To view a list of databases and their size, click «Databases» in the instance string. In the same place it is possible to delete the databases created by users.

Standard databases that always exist:

  • admin
  • local
  • config

User databases appear only after any data is written to them.

Members

To view a list of users and their roles, create new users, change settings, and delete, click «Members» in the instance string.

Roles

Notes:

  • You can specify multiple roles for a single user for different databases.
  • For roles that end in AnyDatabase, the database will always be admin.
  • Role root is not provided.
  • Detailed role descriptions are available at official documentation.

The role of the user determines what actions in which databases he can perform:

  • read - reading from a specific database.
  • readWrite - reading and changing a specific database.
  • dbAdmin - administrative tasks in a particular database (for example, associated with the schema, indexing and collecting statistics).
  • readAnyDatabase - reading from all databases.
  • readWriteAnyDatabase - reading and changing all databases.
  • dbAdminAnyDatabase — administrative tasks in all databases.
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