elasticsearch查询时不区分大小写

"settings": {
    "analysis": {
      "normalizer": {
        "my_normalizer": {
          "type": "custom",
          "filter": ["lowercase", "asciifolding"]
        }
      }
    }
  },

   "mappings": {
    "type": {
      "properties": {
        "foo": {
          "type": "keyword",
          "normalizer": "my_normalizer"
        }
      }
    }
  }