Attribute Names

Users can pick attribute names for document attributes as desired, provided the following attribute naming constraints are not violated:

  • Attribute names starting with an underscore are considered to be system attributes for ArangoDB’s internal use. Such attribute names are already used by ArangoDB for special purposes:
    • _id is used to contain a document’s handle
    • _key is used to contain a document’s user-defined key
    • _rev is used to contain the document’s revision number
    • In edge collections, the
      • _from
      • _to

      attributes are used to reference other documents.

    More system attributes may be added in the future without further notice so end users should try to avoid using their own attribute names starting with underscores.

  • Theoretically, attribute names can include punctuation and special characters as desired, provided the name is a valid UTF-8 string. For maximum portability, special characters should be avoided though. For example, attribute names may contain the dot symbol, but the dot has a special meaning in JavaScript and also in AQL, so when using such attribute names in one of these languages, the attribute name needs to be quoted by the end user. Overall it might be better to use attribute names which don’t require any quoting/escaping in all languages used. This includes languages used by the client (e.g. Ruby, PHP) if the attributes are mapped to object members there.
  • Attribute names starting with an at-mark (@) will need to be enclosed in backticks when used in an AQL query to tell them apart from bind variables. Therefore we do not encourage the use of attributes starting with at-marks, though they will work when used properly.
  • ArangoDB does not enforce a length limit for attribute names. However, long attribute names may use more memory in result sets etc. Therefore the use of long attribute names is discouraged.
  • Attribute names are case-sensitive.
  • Attributes with empty names (an empty string) are disallowed.