Nested compound predicate filters

Open Source Elasticsearch and Kibana
1

Given the document:

{
    "id": 1,
    "school_cd": 18713,
    "assignments": [
        {
            "doc_id": 1,
            "doc_type_id": 11,
            "doc_status": "ASSIGNED"
        },
        {
            "doc_id": 2,
            "doc_type_id": 11,
            "doc_status": "PROCESSED"
        },
        {
            "doc_id": 3,
            "doc_type_id": 19,
            "doc_status": "PROCESSED"
        },
        {
            "doc_id": 4,
            "doc_type_id": 19,
            "doc_status": "ASSIGNED"
        },
        {
            "doc_id": 5,
            "doc_type_id": 19,
            "doc_status": "ASSIGNED"
        }        
    ]
}

I have a query where I want to return a document if the count of the nested assignments elements meets a certain threshold. There are two conditions:

  1. The assignments.doc_type_id == 19, and
  2. The assignments.doc_status == ‘PROCESSED’

I’ve tried the following script, with no luck:

{
    "query": {
        "script": {
            "script": {
                "source": "def count = 0; for (item in doc['assignments']) {if (item.doc_type_id == 11 && item.doc_status.keyword == 'PROCESSED') {count +=1;}} return count <= 2;",
                "lang": "painless"
            },
            "boost": 1.0
        }
    }
}

Which returns an error:

"reason": {
                    "type": "script_exception",
                    "reason": "runtime error",
                    "script_stack": [
                        "org.opensearch.search.lookup.LeafDocLookup.get(LeafDocLookup.java:104)",
                        "org.opensearch.search.lookup.LeafDocLookup.get(LeafDocLookup.java:53)",
                        "for (item in doc['assignments']) {",
                        "                 ^---- HERE"
                    ],
                    "script": "def count = 0; for (item in doc['assignments']) {if (item.doc_type_id == 11 && item.doc_status.keyword == 'PROCESSED') {count +=1;}} return count <= 2;",
                    "lang": "painless",
                    "position": {
                        "offset": 32,
                        "start": 15,
                        "end": 49
                    },
                    "caused_by": {
                        "type": "illegal_argument_exception",
                        "reason": "No field found for [assignments] in mapping with types []"
                    }

Is there another approach to this?