BSON: Difference between revisions

BSON
Filename extension	.bson
Internet media type	none
Type of format	Data interchange
Extended from	JSON
Standard	no RFC yet
Website	bsonspec.org

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Revision as of 14:42, 22 June 2017

BSON /ˈbiːsən/ 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, associative arrays (called objects or documents in MongoDB), and various data types of specific interest to 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)
decimal128 (128-bit IEEE 754 floating point number), suitable as a carrier for arbitrary precision numerics
date (integer number of milliseconds since the Unix epoch)
byte array (binary data)
boolean (true and false)
null
BSON object
BSON array
JavaScript code
MD5 binary data
Regular expression

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 (size of value, value, null terminator)
  \x00                           // 0x00 = type EOO ('end of object')

References

External links

[mime-1] MIME Media Types - The Internet Assigned Numbers Authority

[bsonspec-2] BSON Specification

[json-3] JSON Specification

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[2]

[3]

@@ Line 17: / Line 17: @@
 * integer (32- or 64-bit)
 * double (64-bit [[IEEE 754]] floating point number)
+* decimal128 (128-bit [[IEEE 754]] floating point number), suitable as a carrier for arbitrary precision numerics
 * date (integer number of milliseconds since the [[Unix epoch]])
 * byte array (binary data)