[[query-dsl-fuzzy-query]]
=== Fuzzy Query

The fuzzy query uses similarity based on Levenshtein edit distance for
`string` fields, and a `+/-` margin on numeric and date fields.

==== String fields

The `fuzzy` query generates all possible matching terms that are within  the
maximum edit distance specified in `fuzziness` and then checks the term
dictionary to find out which of those generated terms actually exist in the
index.

Here is a simple example:

[source,js]
--------------------------------------------------
{
    "fuzzy" : { "user" : "ki" }
}
--------------------------------------------------

Or with more advanced settings:

[source,js]
--------------------------------------------------
{
    "fuzzy" : {
        "user" : {
            "value" :         "ki",
            "boost" :         1.0,
            "fuzziness" :     2,
            "prefix_length" : 0,
            "max_expansions": 100
        }
    }
}
--------------------------------------------------

[float]
===== Parameters

[horizontal]
`fuzziness`::

    The maximum edit distance. Defaults to `AUTO`. See <<fuzziness>>.

`prefix_length`::

    The number of initial characters which will not be ``fuzzified''. This
    helps to reduce the number of terms which must be examined. Defaults
    to `0`.

`max_expansions`::

    The maximum number of terms that the `fuzzy` query will expand to.
    Defaults to `0`.


WARNING: this query can be very heavy if `prefix_length` and `max_expansions`
are both set to their defaults of `0`. This could cause every term in the
index to be examined!


[float]
==== Numeric and date fields

Performs a <<query-dsl-range-query>> ``around'' the value using the
`fuzziness` value as a `+/-` range, where:

    -fuzziness <= field value <= +fuzziness

For example:

[source,js]
--------------------------------------------------
{
    "fuzzy" : {
        "price" : {
            "value" : 12,
            "fuzziness" : 2
        }
    }
}
--------------------------------------------------

Will result in a range query between 10 and 14. Date fields support
<<time-units,time values>>, eg:

[source,js]
--------------------------------------------------
{
    "fuzzy" : {
        "created" : {
            "value" : "2010-02-05T12:05:07",
            "fuzziness" : "1d"
        }
    }
}
--------------------------------------------------

See <<fuzziness>> for more details about accepted values.
