MUST_NOT query not working

[rajneesh (Rajneesh Bhardwaj)]

Hi,
I have a query in which i want add a must_not clause to discard all records that have blank data for a particular field. I tried so many ways to do it but none worked. when i issue the same query with few other fields then it works fine.

query:
{
"size": 20,
"_source": [
"registrationType1"
],
"query": {
"bool": {
"must_not": [
{
"term": {
"registrationType1": ""
}
}
]
}
}
}

the results below still contains registrationType1 with empty values

results return:
{

• "took": 3,
• "timed_out": false,
• "_shards": {
  • "total": 5,
  • "successful": 5,
  • "skipped": 0,
  • "failed": 0},
• "hits": {
  • "total": 100689,
  • "max_score": 1,
  • "hits": [
    • {
      • "_index": "oh_animal",
      • "_type": "animals",
      • "_id": "3908021",
      • "_score": 1,
      • "_source": { }}
        , * {
      • "_index": "oh_animal",
      • "_type": "animals",
      • "_id": "3837315",
      • "_score": 1,
      • "_source": {
        • "registrationType1": ""}}
          , * {
      • "_index": "oh_animal",
      • "_type": "animals",
      • "_id": "3842002",
      • "_score": 1,
      • "_source": {
        • "registrationType1": "A&R"}}
          , * {
      • "_index": "oh_animal",
      • "_type": "animals",
      • "_id": "3842033",
      • "_score": 1,
      • "_source": {
        • "registrationType1": "AMHA"}}
          , * {
      • "_index": "oh_animal",
      • "_type": "animals",
      • "_id": "3842213",
      • "_score": 1,
      • "_source": {
        • "registrationType1": "AMHA"}}
          , * {
      • "_index": "oh_animal",
      • "_type": "animals",
      • "_id": "3842963",
      • "_score": 1,
      • "_source": {
        • "registrationType1": ""}}
          , * {
      • "_index": "oh_animal",
      • "_type": "animals",
      • "_id": "3869063",
      • "_score": 1,
      • "_source": {
        • "registrationType1": ""}}

am i missing some mapping configuration ?
mappings for the field above

"registrationType1": {
"type": "text",
"fields": {
"keyword": {
"type": "keyword"
}
}
}