Best way to check if a field exist in an Elasticsearch document

The exists filter has been replaced by exists query from ES 2.1, though the working of it is the same. Also, the missing filter is removed and missing query deprecated.

To get all docs which have a particular field,

"bool": {
    "must": {
        "exists": {
            "field": "my_field"
        }
    }
}

and to get all docs which does NOT have a particular field, use it with must_not like this

"bool": {
    "must_not": {
        "exists": {
            "field": "my_field"
        }
    }
}

Elastic docs: https://www.elastic.co/guide/en/elasticsearch/reference/2.3/query-dsl-missing-query.html

You can use the exists filter combined with a bool/must filter like this:

{
  "query": {
    "filtered": {
      "filter": {
        "bool": {
          "must": [
            {
              "exists": {
                "field": "price"
              }
            },
            ...     <-- your other constraints, if any
          ]
        }
      }
    }
  }
}

DEPRECATED (since ES5) You can also use the missing filter combined with a bool/must_not filter:

{
  "query": {
    "filtered": {
      "filter": {
        "bool": {
          "must_not": [
            {
              "missing": {
                "field": "price"
              }
            }
          ]
        }
      }
    }
  }
}