doesnt_work.sh

curl -XPOST "http://localhost:9200/test/_search?pretty" -d '{
    "filter" : {
        "missing" : {
            "field" : "b"
        }
    }
}'

insert.sh

curl -XPUT http://localhost:9200/test/test/1 -d '{
    "a" : "A1",
    "b" : {
        "b_a" : "b_a 1"
    }
}'

curl -XPUT http://localhost:9200/test/test/2 -d '{
    "abc" : "abc 1"
}'

curl -XPUT http://localhost:9200/test/test/3 -d '{
    "a" : "A3",
    "b" : {
        "b_b" : "b_b 1"
    }
}'

works.sh

curl -XPOST "http://localhost:9200/test/_search?pretty" -d '{
    "filter" : {
        "missing" : {
            "field" : "a"
        }
    }
}'