From Elasticsearch's website:

The _source field contains the original JSON document body that was passed at index time. The _source field itself is not indexed (and thus is not searchable), but it is stored so that it can be returned when executing fetch requests, like get or search

Disabling the source will prevent Elasticsearch from displaying it in the resultset. However, filtering, querying and aggregations will not be affected.

So these two queries will not generate any results in terms of the actual body:

GET mq-body-local/body/_search

GET mq-body-local/body/1

However, you could run this aggregation that will include some of the source, for example:

POST mq-body-local/body/_search

{

  "aggs": {

    "test": {

      "terms": {

        "field": "body"

      }

    }

  }

}

Will produce this result set (I've created some test records):

"aggregations": {

    "test": {

      "doc_count_error_upper_bound": 0,

      "sum_other_doc_count": 0,

      "buckets": [

        {

          "key": "my body",

          "doc_count": 1

        },

        {

          "key": "my body2",

          "doc_count": 1

        }

      ]

    }

  }