What is the best way to disable the default analyzer....

not_analyzed_by_default

{
    "template": "prefix-*",
     "mappings": {
        "_default_": { 
            "_source": { "compress": true },
            "dynamic_templates": [
                {
                    "string_template" : { 
                        "match" : "*",
                        "mapping": { "type": "string", "index": "not_analyzed" },
                        "match_mapping_type" : "string"
                     } 
                 }
             ]
        }
    }
}