事實上，_source 字段就是1個貯存字段。
在 Elasticsearch 中，單獨設置貯存字段不是1個好做法。完全的文檔已被保存在 _source 字段中。
通常最好的辦法會是使用 _source 參數來過濾你需要的字段。

_source禁用，如何搜索到字段值？

必須設置所有字段：store：true
如果mapping中，對某個type，設置了 “_source”: {“enabled”: false}，那末查詢結果中就沒有_source字段只能查到文檔id。

如果mapping中，field設置了store為true，例如 “age”:{“type”:”integer”,”store”:true}，那末就能夠在查詢時通過指定fields獲得到指定的field的數據。

store默許false。

fielddata_fields 和 fields區分？
fielddata_fields同時還返回_source, fields不返回_source。

• field data fields(fielddata_fields) can work on fields that are not stored(from _source),will cause the terms for that field to be loaded to memory (cached),
• fields parameter（fields） is about fields that are explicitly marked as stored in the mapping, which is off by default and generally not recommended.

https://www.elastic.co/guide/en/elasticsearch/reference/2.1/search-request-fielddata-fields.html
https://www.elastic.co/guide/en/elasticsearch/reference/2.1/search-request-fields.html

REST:
https://www.elastic.co/guide/en/elasticsearch/reference/2.1/search-request-fields.html

{
    "fields" : ["user", "postDate"],
    "query" : {
        "term" : { "user" : "kimchy" }
    }
}

Java API

SearchRequestBuilder類
方法：addFields(String... fields)
或：addField(String field) 

建索引時，指定_souce存儲的字段？

默許存儲所有字段

PUT logs
{
  "mappings": {
    "event": {
      "_source": {
        "includes": [
          "*.count",
          "meta.*"
        ],
        "excludes": [
          "meta.description",
          "meta.other.*"
        ]
      }
    }
  }
}

控制從_source返回部份字段

GET /_search
{
    "query":   { "match_all": {}},
    "_source": [ "title", "created" ]
}
//支持通配符
{
    "_source": "obj.*",
    "query" : {
        "term" : { "user" : "kimchy" }
    }
}

{
    "_source": [ "obj1.*", "obj2.*" ],
    "query" : {
        "term" : { "user" : "kimchy" }
    }
}

{
    "_source": {
        "include": [ "obj1.*", "obj2.*" ],
        "exclude": [ "*.description" ]
    },
    "query" : {
        "term" : { "user" : "kimchy" }
    }
}