An Elasticsearch gist for the thread "exist filter also matching on nested fields": https://groups.google.com/forum/#!topic/elasticsearch/8R9XgVkCZIU

Elasticsearch: exist filter also matching on nested fields

# Remove old data
curl -XDELETE "http://localhost:9200/nestedfiltertest?pretty"
 
# Create index with nested type mapping
curl -XPUT "http://localhost:9200/nestedfiltertest/?pretty" -d '
{
   "mappings": {
      "doc": {
         "properties": {
            "nested": {
               "type": "nested",
               "properties": {
                  "group_id": {
                     "type": "string"
                  }
               }
            }
         }
      }
   }
}'

# Index some data
curl -XPUT "http://localhost:9200/nestedfiltertest/doc/1?pretty" -d '
{
   "group_id": "xxx"
}'

curl -XPUT "http://localhost:9200/nestedfiltertest/doc/2?pretty" -d '
{
   "nested": {
      "group_id": "xxx"
   }
}'

curl -XPUT "http://localhost:9200/nestedfiltertest/doc/3?pretty" -d '
{
   "abc": "yyy"
}'

curl -XPOST 'http://localhost:9200/nestedfiltertest/_flush?pretty'

echo "### Test query: ###"
curl -XPOST "http://localhost:9200/nestedfiltertest/_search?pretty" -d '
{
   "query": {
      "filtered": {
         "query": {
            "match_all": {}
         },
         "filter": {
            "exists": {
               "field": "group_id"
            }
         }
      }
   }
}'