Painless Convert "-" to ""

Painless convert_-_to_empty_String.json

# test the pipeline using the simulate API
POST _ingest/pipeline/_simulate
{
  "docs": [
    {
      "_index": "index",
      "_source": {
        "leave_as_abc": "abc",
        "change_to_empty1": "-",
        "more_tests": {
          "leave_as_def": "def",
          "leave_as_date": "2016-11-16T23:00:00.000Z",
          "leave_as_true": true
        },
        "nested_tests": {
          "level2": {
            "level3": {
              "level4": {
                "level5": {
                  "change_to_empty2": "-"
                }
              }
            }
          }
        }
      }
    }
  ],
  "pipeline": {
    "description": "recurse over properties map and convert - to empty string",
    "processors": [
      {
        "script": {
          "source": """
void traverse(Map o) {
  for (String childKey : o.keySet()) {
    if (!childKey.substring(0,1).equals("_")) {
      def child = o.get(childKey);
      if (child instanceof Map) {
        traverse(child);
      } else if (child instanceof String) {
        if (child.equals("-"))
          o[childKey] = "";
      }
    }
  }
}
  
traverse(ctx)
"""
        }
      }
    ]
  }
}