How to modify the content of the field in source?

Elastic Stack Elasticsearch
1

I want to process the query return value of the document in the source code and implement the following operations:

index:

{ "id": 1001,
"title":"abcd"
}

return:

{
"id": 1001,
"title": "bcde"
}

That is, replace the field, and the length of the string before and after the replacement is the same.

How to achieve this goal？

2

Welcome!

May be runtime fields could help. From the doc (emphasis is mine):

A runtime field is a field that is evaluated at query time. Runtime fields enable you to:

  • Add fields to existing documents without reindexing your data
  • Start working with your data without understanding how it’s structured
  • Override the value returned from an indexed field at query time
  • Define fields for a specific use without modifying the underlying schema