Painless script to add new fields into _source object when querying into elasticsearch v6.0.1 - elasticsearch

Question

I have an index with the field mapping with one property (id: integer).
When I am querying into that index, I am able to get the correct response. Now, I want to add one extra fields into _source object at the query time using painless scripting.
The elasticsearch version is 6.0.1.
I have already tried adding script as a field in the query block. But it throws an error:
{
"error": {
"root_cause": [
{
"type": "parsing_exception",
"reason": "[term] malformed query, expected [END_OBJECT] but found [FIELD_NAME]",
"line": 7,
"col": 7
}
],
"type": "parsing_exception",
"reason": "[term] malformed query, expected [END_OBJECT] but found [FIELD_NAME]",
"line": 7,
"col": 7
},
"status": 400
}
GET 20190719_candidate/candidate/_search
{
"min_score": 0.001,
"query": {
"term": {
"id": 1234
},
"script": {
"script": {
"inline": "doc['field_1'] = 'field_1_value'"
}
}
},
"from": 0,
"size": 20
}
The expected result for _source object is:
{
"id": "1234567",
"field_1": "field_1_value"
}

Answer 1

You are missing the structure:
GET 20190719_candidate/candidate/_search
{
"min_score": 0.001,
"query": {
"term": {
"id": 1234
},
"script_fields": {
"test1":{
"script": {
"lang": "painless",
"source": "'field_1_value'"
}
}
}
},
"from": 0,
"size": 20
}
Take a look in this example:
GET /_search
{
"query" : {
"match_all": {}
},
"script_fields" : {
"test1" : {
"script" : {
"lang": "painless",
"source": "doc['price'].value * 2"
}
},
"test2" : {
"script" : {
"lang": "painless",
"source": "doc['price'].value * params.factor",
"params" : {
"factor" : 2.0
}
}
}
}
}
source: https://www.elastic.co/guide/en/elasticsearch/reference/current/search-request-body.html#request-body-search-script-fields

Answer 2

"root_cause": [
{
"type": "parsing_exception",
"reason": "[term] malformed query, expected [END_OBJECT] but found [FIELD_NAME]",
"line": 7,
"col": 7
}
],
the error says that you have a malformed query, you have missed a closing bracket in line 7 to close the "query" attribute.
you query should be like:
GET 20190719_candidate/candidate/_search
{
"min_score": 0.001,
"query": {
"term": {
"id": 1234
}},
"script": {
"lang": "painless",
"inline": "doc['field_1'] = 'field_1_value'"
},
"from": 0,
"size": 20
}