Sorting by a nested field in elasticsearch - elasticsearch

Question

If I had a data structure that looked like this
[{"_id" 1
"scores" [{"student_id": 1, "score": 100"}, {"student_id": 2, "score": 80"}
]},
{"_id" 2
"scores" [{"student_id": 1, "score": 20"}, {"student_id": 2, "score": 90"}
]}]
Would it be possible to sort this dataset by student_1's score or by student_2's score?
For example if I sorted descending by student 1's score, I would get document 1,2, but if I sorted descending by student 2's score, I would get 2,1.
I could re-arrange the data, but I don't want to use another index because there's a bunch of metadata not included above for brevity. Thanks!

Answer 1

Yes, it is possible. You must use "nested" field type for your scores, that way you can keep the relation between each student_id and its score.
You can read an article I wrote about that subject:
https://opster.com/guides/elasticsearch/data-architecture/elasticsearch-nested-field-object-field/
Now the example:
Mappings
PUT test_students
{
"mappings": {
"properties": {
"scores": {
"type": "nested",
"properties": {
"student_id": {
"type": "keyword"
},
"score": {
"type": "long"
}
}
}
}
}
}
Documents
PUT test_students/_doc/1
{
"scores": [{"student_id": 1, "score": 100}, {"student_id": 2, "score": 80}]
}
PUT test_students/_doc/2
{
"scores": [{"student_id": 1, "score": 20}, {"student_id": 2, "score": 90}]
}
Query
POST test_students/_search
{
"sort" : [
{
"scores.score" : {
"mode" : "max",
"order" : "desc",
"nested": {
"path": "scores",
"filter": {
"term" : { "scores.student_id" : "2" }
}
}
}
}
]
}