Joining multiple document within same index with joining the key

Elastic Stack Elasticsearch
1

Just have an question on query to join multiple document together.
For example , i have the following 6 document into same index:

{
"_id" : 1,
"studentId" : "a11",
"class" : "1A",
"classNumber" : 11
},
{
"_id" : 2,
"studentId" : "a11",
"hobby" :"swimming"
},
{
"_id" : 3,
"studentId" : "a11",
"Country" : "USA"
},
{
"_id" : 4,
"studentId" : "b22",
"class" : "1B",
"classNumber" : 50
},
{
"_id" : 5,
"studentId" : "b22",
"hobby" :"cooking"
},
{
"_id" : 6,
"studentId" : "c33",
"Country" : "USA"
}

May i know if i may use DSL query to join the document together based on a key (e.g. "studentId") and become like this?

{
"_id" : 1,
"studentId" : "a11",
"class" : "1A",
"classNumber" : 11
"hobby" :"swimming"
"Country" : "USA"
},
{
"_id" : 4,
"studentId" : "b22",
"class" : "1B",
"classNumber" : 50
"hobby" :"cooking"
},
{
"_id" : 6,
"studentId" : "c33",
"Country" : "USA"
}

Or i need to create a new index? Any other suggestion are welcome.

2

Elasticsearch does not support joins so I would recommend indexed by the data as you want to retrieve and query it.

3

what you mean is prepare the data first (deformalized it first) and put in index?

4

Yes.

5

But sometime we cannot deformalize it from the beginning . (e.g. they are insert in different timestamp by restful API). So in this case we need to and another layer to join it first before put in index? No other choice?

6

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