Right way access parent field in Elasticsearch nested aggs script - elasticsearch

Question

Elasticsearch Version: 5.6.3
I have a mapping like this:
PUT /my_stock
{
"mappings": {
"stock": {
"properties": {
"industry": {
"type": "nested",
"properties": {
"name": {
"type": "keyword"
},
"rate": {
"type": "double"
}
}
},
"changeRatio": {
"type": "double"
}
}
}
}
}
Datas:
POST /_bulk
{"index":{"_index":"my_stock","_type":"stock","_id":null}}
{"industry":[{"name":"Technology","rate":0.6},{"name":"Health", "rate":0.2}],"changeRatio":0.1}
{"index":{"_index":"my_stock","_type":"stock","_id":null}}
{"industry":[{"name":"Health", "rate":0.3},{"name":"Education", "rate":0.2}],"changeRatio":0.2}
{"index":{"_index":"my_stock","_type":"stock","_id":null}}
{"industry":[{"name":"Health","rate":0.5},{"name":"Education","rate":0.2}],"changeRatio":-0.3}
{"index":{"_index":"my_stock","_type":"stock","_id":null}}
{"industry":[{"name":"Technology","rate":0.3},{"name":"Education","rate":0.3}],"changeRatio":0.4}
{"index":{"_index":"my_stock","_type":"stock","_id":null}}
{"industry":[{"name":"Education","rate":0.3},{"name":"Technology","rate":0.1}],"changeRatio":-0.5}
I then want to build a aggs query like this:
GET my_stock/stock/_search
{
"size": 0,
"aggs": {
"industry": {
"nested": {
"path": "industry"
},
"aggs": {
"groups": {
"terms": {
"field": "industry.name",
"order": {
"rate": "desc"
}
},
"aggs": {
"rate": {
"sum": {
"script": {
"source": "doc['changeRatio'].value * doc['industry.rate'].value"
}
}
}
}
}
}
}
}
}
but "doc['changeRatio'].value" can't get right value, it's always return 0
another query like this:
GET my_stock/stock/_search
{
"size": 0,
"aggs": {
"industry": {
"nested": {
"path": "industry"
},
"aggs": {
"groups": {
"terms": {
"field": "industry.name",
"order":{
"reverse>rate":"desc"
}
},
"aggs": {
"reverse": {
"reverse_nested": {},
"aggs": {
"rate": {
"sum": {
"script": {
"source": "doc['changeRatio'].value * doc['industry.rate'].value"
}
}
}
}
}
}
}
}
}
}
}
"doc['changeRatio'].value" is right, but "doc['industry.rate'].value" get 0
Refer to this question: Elasticsearch 5.4: Use normal and nested fields in same Painless script query?
1. { params['_source']['changeRatio'] } or { params['_source']['industry.rate'] } not work in this version
2. "copy to" stored as a multivalue field, also not working
How can i make a correct script get "changeRatio * industry.rate"?