We’re overhauling Dgraph’s docs to make them clearer and more approachable. If you notice any issues during this transition or have suggestions, please let us know.

A @lang directive must be specified in the schema to query or mutate predicates with language tags.

Dgraph supports UTF-8 strings.

In a query, for a string valued edge edge, the syntax

edge@lang1:...:langN

specifies the preference order for returned languages, with the following rules.

  • At most one result is returned (except in the case where the language list is set to *).
  • The preference list is considered left to right: if a value in given language isn’t found, the next language from the list is considered.
  • If there are no values in any of the specified languages, no value is returned.
  • A final . means that a value without a specified language is returned or if there is no value without language, a value in ”some” language is returned.
  • Setting the language list value to * returns all the values for that predicate along with their language. Values without a language tag are also returned.

For example:

  • name => Look for an untagged string; return nothing if no untagged value exits.
  • name@. => Look for an untagged string, then any language.
  • name@en => Look for en tagged string; return nothing if no en tagged string exists.
  • name@en:. => Look for en, then untagged, then any language.
  • name@en:pl => Look for en, then pl, otherwise nothing.
  • name@en:pl:. => Look for en, then pl, then untagged, then any language.
  • name@* => Look for all the values of this predicate and return them along with their language. For example, if there are two values with languages en and hi, this query returns two keys named “name@en” and “name@hi”.

In functions, language lists (including the @* notation) aren’t allowed. Untagged predicates, Single language tags, and . notation work as described above.

In full-text search functions (alloftext, anyoftext), when no language is specified (untagged or @.), the default (English) full-text tokenizer is used. This does not mean that the value with the en tag will be searched when querying the untagged value, but that untagged values will be treated as English text. If you don’t want that to be the case, use the appropriate tag for the desired language, both for mutating and querying the value.

Query Example: some of Bollywood director and actor Farhan Akhtar’s movies have a name stored in Russian as well as Hindi and English, others do not.

query {
  q(func: allofterms(name@en, "Farhan Akhtar")) {
    name@hi
    name@en

    director.film {
      name@ru:hi:en
      name@en
      name@hi
      name@ru
    }
  }
}