http://192.168.32.81:9200/library/books/8/                              GET{    "_index": "library",    "_type": "books",    "_id": "8",    "_version": 1,    "found": true,    "_source": {        "titile": "Elasticsearch: The Defintive Guide",        "name": {            "first": "Zachary",            "last": "Tong"        },        "publish_date": "2016-07-29",        "price": "90.01"    }}此时版本为  "_version": 1,http://192.168.32.81:9200/library/books/8/_update                               POST{  "doc":{      "price":"11.13"} }{    "_index": "library",    "_type": "books",    "_id": "8",    "_version": 2,    "found": true,    "_source": {        "titile": "Elasticsearch: The Defintive Guide",        "name": {            "first": "Zachary",            "last": "Tong"        },        "publish_date": "2016-07-29",        "price": "11.13"    }}此时版本变为2