"exists" query on geo_point property with doc_values=false incorrectly matches documents with a null value

[yrodiere]

Elasticsearch version (bin/elasticsearch --version): docker.elastic.co/elasticsearch/elasticsearch-oss:7.10.0

Plugins installed: []

JVM version (java -version): N/A (using container)

OS version (uname -a if on a Unix-like system): N/A (using container)

Description of the problem including expected versus actual behavior:

The exists query does not behave properly for geo_point properties when doc_values are set to false.

It will match all documents that have a value set for this property, even if that value is null.

I would expect documents whose value is null not to be matched by the exists query.

This is inconsistent in multiple ways:

• ES 7.10 considers null as non-existing for geo_point properties with doc_values set to true (the default).
• ES 7.10 considers null as non-existing for other property types.
• Previous versions of Elasticsearch consider null as non-existing for geo_point properties. I tested 7.9.2 with the reproducer below in order to confirm this.

Steps to reproduce:

docker run -it --rm=true --name elasticsearch_test -p 9200:9200 -p 9300:9300 -e "discovery.type=single-node" docker.elastic.co/elasticsearch/elasticsearch-oss:7.10.0
curl -X PUT "localhost:9200/test-geopoint?pretty" -H 'Content-Type: application/json' -d'                                                             
{
  "mappings": {
    "properties": {
      "geopoint": {
        "type": "geo_point", "doc_values": false
      }
    }
  }
}
'
curl -X PUT "localhost:9200/test-geopoint/_doc/existing" -H 'Content-Type: application/json' -d'{"geopoint":{"lat": 42.0, "lon": 43.0}}'
curl -X PUT "localhost:9200/test-geopoint/_doc/empty" -H 'Content-Type: application/json' -d'{}'
curl -X PUT "localhost:9200/test-geopoint/_doc/null" -H 'Content-Type: application/json' -d'{"geopoint":null}'
curl -X POST "localhost:9200/test-geopoint/_search/?pretty" -H 'Content-Type: application/json' -d'{ "query": { "exists": { "field": "geopoint" } } }'

The search query returns the document that has a null value for its geo_point property:

{
  "took" : 50,
  "timed_out" : false,
  "_shards" : {
    "total" : 1,
    "successful" : 1,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "total" : {
      "value" : 2,
      "relation" : "eq"
    },
    "max_score" : 1.0,
    "hits" : [
      {
        "_index" : "test-geopoint",
        "_type" : "_doc",
        "_id" : "existing",
        "_score" : 1.0,
        "_source" : {
          "geopoint" : {
            "lat" : 42.0,
            "lon" : 43.0
          }
        }
      },
      {
        "_index" : "test-geopoint",
        "_type" : "_doc",
        "_id" : "null",
        "_score" : 1.0,
        "_source" : {
          "geopoint" : null
        }
      }
    ]
  }
}

[elasticmachine]

Pinging @elastic/es-search (Team:Search)

[elasticmachine]

Pinging @elastic/es-analytics-geo (Team:Analytics)