How to return hit term in ES ？ - elasticsearch

Question

I try to return only the terms that were successfully hit instead of the document itself, but I don’t know how to achieve the desired effect。
"es_episode" : {
"aliases" : { },
"mappings" : {
"properties" : {
"endTime" : {
"type" : "long"
},
"episodeId" : {
"type" : "long"
},
"startTime" : {
"type" : "long"
},
"studentIds" : {
"type" : "long"
}
}
}
This is an example:
{
"episodeId":124,
"startTime":10,
"endTime":20,
"studentIds":[200,300]
}
My query:
GET /es_episode/_search
{
"_source": ["studentIds"],
"query": {
"terms": {
"studentIds": [300,400]
}
}
}
The result is
"hits" : {
"total" : {
"value" : 1,
"relation" : "eq"
},
"max_score" : 1.0,
"hits" : [
{
"_index" : "es_episode",
"_type" : "episode",
"_id" : "2",
"_score" : 1.0,
"_source" : {
"studentIds" : [
200,
300
]
}
}
]
}
But in fact I only want to know which term hits. For example, the result I want should be studentIds=[300] instead of all studentIds=[200,300] of the returned document. It seems that some additional operations are required, but I don’t know
how.
I try to achieve my goal with the following query
GET /es_episode/_search
{
"_source": ["studentIds"],
"query": {
"terms": {
"studentIds": [300,400]
}
},
"aggs": {
"student_id": {
"terms": {
"field": "studentIds",
"size": 10
},
"aggs": {
"id": {
"terms": {
"field": "episodeId"
}
},
"id_select":{
"bucket_selector": {
"buckets_path": {
"key" : "_key"
},
"script": "params.key==300 || params.key==400"
}
}
}
}
}
}
the result for this is
"aggregations" : {
"student_id" : {
"doc_count_error_upper_bound" : 0,
"sum_other_doc_count" : 0,
"buckets" : [
{
"key" : 300,
"doc_count" : 1,
"id" : {
"doc_count_error_upper_bound" : 0,
"sum_other_doc_count" : 0,
"buckets" : [
{
"key" : 124,
"doc_count" : 1
}
]
}
}
]
}
}
It seems that I successfully filtered out the terms I don’t want, but this doesn’t look pretty, and I need to set my parameters repeatedly in the script