Whole attachment in _source when searching attachments

Elastic Stack Elasticsearch
1

I am basically indexing pdfs.

Then I am searching them and I am using the highlight field to preview the search results.

The problem is, that for each search query, I am getting the whole attachment back in the _source field.
Is there a way to disable this?

My search query:

POST /documents/document/_search
{
  "query": {
    "multi_match": {
      "query": "Fault",
      "fields": ["author^2","tags","doc.content"]
    }},
    "highlight" : {
        "fields" : {
            "*" : {}
        } 
    }
  }

And my schema:

POST /documents
{
  "mappings": {
    "document": {
      "properties": {
        "doc": {
          "type": "attachment",
          "fields": {
            "content": {
              "type": "string",
              "term_vector": "with_positions_offsets",
              "store": true
            }
          }
        },
        "author": {
          "type": "string"
        },
        "pub_date": {
          "type": "date"
        },
        "tags": {
          "type": "string"
        }
      }
    }
  }
}
2

You can use source filtering: https://www.elastic.co/guide/en/elasticsearch/reference/2.3/search-request-source-filtering.html