How to create unique constraint in Elasticsearch database?

Question

I am using elasticsearch as a document database and each record I create has a guid id that the system uses for the record id. Business people want to offer a feature to let

Answer 1

So far as to ES 7.5, there is no such extra "constraint" to ensure uniqueness using a custom field in the mapping.

But you still can walk around it via your own application UUID, which could be used directly explicitly as the _id (which is unique implictly) to achieve your goals.

PUT /_doc/
{
  "a_field": "a_value"
}