Hello:
I've upgraded my cluster to 5.0 these days.
And i found the index size is bigger than 1.3.
The following is the index metadata in 5.0:
"_all": {
    "search_analyzer": "default_search",
    "analyzer": "default",
    "enabled": false
    },
    "properties": {
    "heat": {
    "type": "integer"
    },
    "_nid": {
    "type": "keyword",
    "doc_values": false
    },
    "channel": {
    "type": "keyword",
    "doc_values": false
    },
    "_tid": {
    "type": "long"
    },
    "title": {
    "index": false,
    "type": "keyword"
    }
    }
And the metadata in 1.3:
 "_all": {
    "enabled": false
    },
    "properties": {
    "heat": {
    "type": "integer"
    },
    "_nid": {
    "index": "not_analyzed",
    "type": "string"
    },
    "channel": {
    "index": "not_analyzed",
    "type": "string"
    },
    "_tid": {
    "type": "long"
    },
    "title": {
    "index": "no",
    "type": "string"
    }
    }
Thanks