BSON

BSON /ˈbiːsɒn/ is a computer data interchange format used mainly as a data storage and network transfer format in the MongoDB database. It is a binary form for representing simple data structures and associative arrays (called objects or documents in MongoDB). The name "BSON" is based on the term JSON and stands for "Binary JSON".^[2]

Data types and syntax

BSON documents (objects) consist of an ordered list of elements. Each element consists of a field name, a type, and a value. Field names are strings. Types include:

• string
• integer (32- or 64-bit)
• double (64-bit IEEE 754 floating point number)
• date (integer number of milliseconds since the Unix epoch)
• byte array (binary data)
• boolean (true and false)
• null
• BSON object
• BSON array

BSON types are nominally a superset of JSON types (JSON does not have a date or a byte array type, for example^[3]), with one exception of not having a universal "number" type as JSON does.

Efficiency

Compared to JSON, BSON is designed to be efficient both in storage space and scan-speed. Large elements in a BSON document are prefixed with a length field to facilitate scanning. In some cases, BSON will use more space than JSON due to the length prefixes and explicit array indices.^[2]

Example

A document such as hello="world" will be stored as:

Bson:
  \x16\x00\x00\x00                   // total document size
  \x02                               // 0x02 = type String
  hello\x00                          // field name
  \x06\x00\x00\x00world\x00          // field value
  \x00                               // 0x00 = type EOO ('end of object')

See also

• JSON
• Smile (binary JSON)
• UBJSON
• Protocol Buffers
• Action Message Format
• Apache Thrift
• MessagePack
• Document-oriented database
  • MongoDB
• Abstract Syntax Notation One (ASN.1)
• Wireless Binary XML (WBXML)
• Efficient XML Interchange
• Sereal

References

External links

• BSON Specification
• BSON documentation on the MongoDB website
• bsondump tool included with MongoDB