How to fetch the data from the nested structured data ? in elastic search

Elastic Stack Elasticsearch
1

{
"group" : "fans",
"user" : [
{
"first" : "John",
"last" : "Smith"
},
{
"first" : "Alice",
"last" : "White"
},
]
}
i need to fetch the user's firstname only

2

You can use the fields parameter to limit the fields in your output. So if e.g. you model the user as nested objects and run a nested_query you can then filter with "fields": ["user.first"] and the output will only contain that field.