Is there a way to compare string alphabetically in painless - elasticsearch

Question

I would like to execute this kind of operation in painless :
if (_value >= 'c)' {
return _value
} else {
return '__BAD__'
}
value is a string and I would like this following behaviour :
if value is foo I want to replace it with __BAD__ if the value is bar, I want to keep bar. only values alphabetically after 'c' should be set to __BAD__.
I got this exception :
"lang": "painless",
"caused_by": {
"type": "class_cast_exception",
"reason": "Cannot apply [>] operation to types [java.lang.String] and [java.lang.String]."
}
Is there a way to perform string alphabetical comparaison between string in painless ?
My documents are looking :
{
"id": "doca",
"categoryId": "aaa",
"parentNames": "a$aa$aaa"
},
{
"id": "docb",
"categoryId": "bbb",
"parentNames": "a$aa$bbb"
},
{
"id": "docz",
"categoryId": "zzz",
"parentNames": "a$aa$zzz"
}
and my query is like :
{
"query": {
"bool": {
"filter": []
}
},
"size": 0,
"aggs": {
"catNames": {
"terms": {
"size": 10000,
"order": {
"_key": "asc"
},
"script": {
"source": "if(doc['parentNames'].value < 'a$aa$ccc') {return doc['parentNames'].value} return '__BAD__'",
"lang": "painless"
}
},
"aggs": {
"sort": {
"bucket_sort": {
"size": 2
}
},
"catId": {
"terms": {
"field": "categoryId",
"size": 1
}
}
}
}
}
}
I am expecting the result :
{
"took": 29,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"skipped": 0,
"failed": 0
},
"hits": {
"total": 3,
"max_score": 0,
"hits": []
},
"aggregations": {
"catNames": {
"doc_count_error_upper_bound": 0,
"sum_other_doc_count": 0,
"buckets": [
{
"key": "__BAD__",
"doc_count": 1,
"catId": {
"buckets": [
{
"key": "aaa",
"doc_count": 1
}
]
}
},
{
"key": "a$aa$bbb",
"doc_count": 1,
"catId": {
"buckets": [
{
"key": "bbb",
"doc_count": 1
}
]
}
},
{
"key": "a$aa$zzz",
"doc_count": 1,
"catId": {
"buckets": [
{
"key": "zzz",
"doc_count": 1
}
]
}
}
]
}
}
}

Answer 1

In fact, I can use the compareTo function of java.lang.String.
if (_value.compareTo('c') > 0) {
return _value
} else {
return '__BAD__'
}
My query is becoming :
{
"query": {
"bool": {
"filter": []
}
},
"size": 0,
"aggs": {
"catNames": {
"terms": {
"size": 10000,
"order": {
"_key": "asc"
},
"script": {
"source": "if(doc['parentNames'].value.compareTo('a$aa$ccc')) {return doc['parentNames'].value} return '__BAD__'",
"lang": "painless"
}
},
"aggs": {
"sort": {
"bucket_sort": {
"size": 2
}
},
"catId": {
"terms": {
"field": "categoryId",
"size": 1
}
}
}
}
}
}