Exact Filter on array field in elasticsearch

sense.json

DELETE /blog
PUT /blog
{
  "settings":{
    "analysis":{
      "analyzer":{
        "mykeyword":{
          "type":"custom",
          "tokenizer":"keyword"
        }
      }
    }
  },
  "mappings": {
    "articles":{
      "properties": {
        "tags":{
          "type": "string"
          , "index": "not_analyzed"
        },
        "tagz":{
          "type": "string"
          , "analyzer": "mykeyword"
        }
      }
    }
  }
}
GET /blog/articles/_mapping
PUT /blog/articles/1
{
  "tags":["UPPER","lower"],
  "tagz":["UPPER","lower"]
}
PUT /blog/articles/2
{
  "tags":["UPPER"],
  "tagz":["UPPER"]
}
PUT /blog/articles/3
{
  "tags":["lower"],
  "tagz":["lower"]
}

GET /blog/articles/_search

GET /blog/articles/_search
{
  "query": {"filtered": {
    "query": {"match_all": {}},
    "filter": {
      "bool": {"must": [
        {"term": {
          "tags": "UPPER"
        }}
      ]}
    }
  }}
}
GET /blog/articles/_search
{
  "query": {"filtered": {
    "query": {"match_all": {}},
    "filter": {
      "bool": {"must": [
        {"term": {
          "tagz": "UPPER"
        }}
      ]}
    }
  }}
}
GET /blog/articles/_search
{
  "query": {"filtered": {
    "query": {"match_all": {}},
    "filter": {
      "bool": {"must": [
        {"term": {
          "tagz": "upper"
        }}
      ]}
    }
  }}
}