Elastic - JSON Array nested in Array - arrays

Question

I have to index a json to Elastic which look like the below format. My problem is that the key "variable" is array that contains json objects (I thought about "nested" datatype of Elastic) but some of those objects it's possible to contain nested json arrays inside them. (see variable CUSTOMERS).
POST /example_data/data {
"process_name": "TEST_PROCESS",
"process_version ": 0,
"process_id": "1111",
"activity_id": "111",
"name": "update_data",
"username": "testUser",
"datetime": "2018-01-01 10:00:00",
"variables": [{
"name": "ΒΑΝΚ",
"data_type": "STRING",
"value": "EUROBANK"
},{
"name": "CITY",
"data_type": "STRING",
"value": "LONDON"
}, {
"name": "CUSTOMERS",
"data_type": "ENTITY",
"value": [{
"variables": [{
"name": "CUSTOMER_NAME",
"data_type": "STRING",
"value": "JOHN"
}, {
"name": " CUSTOMER_CITY",
"data_type": "STRING",
"value": "LONDON"
}
]
}
]
}, {
"name": "CUSTOMERS",
"data_type": "ENTITY",
"value": [{
"variables": [{
"name": "CUSTOMER_NAME",
"data_type": "STRING",
"value": "ΑΘΗΝΑ"
}, {
"name": " CUSTOMER_CITY ",
"data_type": "STRING",
"value": "LIVERPOOL"
}, {
"name": " CUSTOMER_NUMBER",
"data_type": "STRING",
"value": "1234567890"
}
]
}
]
}
] }
When I'm trying to index it I get the following error
{ "error": {
"root_cause": [
{
"type": "illegal_argument_exception",
"reason": "Can't merge a non object mapping [variables.value] with an object mapping [variables.value]"
}
],
"type": "illegal_argument_exception",
"reason": "Can't merge a non object mapping [variables.value] with an object mapping [variables.value]" }, "status": 400 }
Mapping
{ "example_data": {
"mappings": {
"data": {
"properties": {
"activity_id": {
"type": "text"
},
"name": {
"type": "text"
},
"process_name": {
"type": "text"
},
"process_version": {
"type": "integer"
}
"process_id": {
"type": "text"
},
"datetime": {
"type": "date",
"format": "yyyy-MM-dd HH:mm:ss"
},
"username": {
"type": "text",
"analyzer": "greek"
},
"variables": {
"type": "nested",
"properties": {
"data_type": {
"type": "text",
"fields": {
"keyword": {
"type": "keyword",
"ignore_above": 256
}
}
},
"name": {
"type": "text",
"fields": {
"keyword": {
"type": "keyword",
"ignore_above": 256
}
}
},
"value": {
"type": "text",
"fields": {
"keyword": {
"type": "keyword",
"ignore_above": 256
}
}
}
}
}
}
}
}}}
When I remove the variable CUSTOMERS that contains the array, then It works properly because there are only json objects.
Is there a way to handle that? Thanks in advance