Query on array

[Segfault]

Hello world,

I'm trying to query with a filter to restrict array size. (Only get the results that have more than 1 object inside the transactions array)
I can't manage to get it working. I hope some people here have some ideas to help me.

My mapping is the following:

{
	"properties": {
		"userId": {"type": "keyword"},
		"shopId": {"type": "keyword"},
		"transactions": {
			"type": "nested",
			"properties": {
				"date": {"type": "text"},
				"commissionStatus": {"type": "text"},
				"commissionAmount": {"type": "float"},
				"commissionAmountTicker": {"type": "text"},
				"saleAmount": {"type": "float"},
				"saleCurrencyTicker": {"type": "text"},
				"id": {"type": "text"},
				"type": {"type": "text"},
				"network": {"type": "text"}
			}
		}
	}
}

I'm trying to do the following query:

{
	"query": {
		"bool": {
		  "must": [{
		    "match": {"shopId":"5109468509503488"}
		  }],
		  "filter": [{
	        "range" : {
	            "@timestamp" : {
	                "gte":  "now-7d/d",
	                "lte": "now/d"
	            }
	        }
		  },
		  {
		  	"script": {
	        	"script": {
	        		"source": "doc['transactions'].length >= 1",
	        		"lang": "painless"
	        	}
	        }
		  }]
		}
	},
	"size": 1
}

But I get an error:

"failed_shards": [
{
"shard": 0,
"index": "transactions",
"node": "TpzdGPfjTjejIAnk4mSgEg",
"reason": {
"type": "script_exception",
"reason": "runtime error",
"script_stack": [
"org.elasticsearch.search.lookup.LeafDocLookup.get(LeafDocLookup.java:94)",
"org.elasticsearch.search.lookup.LeafDocLookup.get(LeafDocLookup.java:41)",
"doc['transactions'].length >= 1",
" ^---- HERE"
],
"script": "doc['transactions'].length >= 1",
"lang": "painless",
"caused_by": {
"type": "illegal_argument_exception",
"reason": "No field found for [transactions] in mapping with types "
}
}
}
]

Thank you for your help.