Mapper Parsing Exception for field with date data that I want to index as a string

I think this might be the same issue as of https://github.com/elastic/elasticsearch/pull/22174

I tested it with 5.3 and master and it looks like it's fixed.

As a workaround you can add the explicit date format to the dynamic mapping for the date field:

                "date_fields": {
                    "mapping": {
                        "type": "date",
                        "format": "yyyy/MM/dd",
                        "doc_values": true
                    },
                    "match": "*",
                    "match_mapping_type": "date"
                }