When creating an index, what is the point of '_doc' when defining the mapping of the index?

Question

As I understand, when creating an index, you can define the fields that the documents will have in that index by defining a mapping

PUT person
{
  "mappings": {
    "properties": {
      "firstName":{"type":"text"},
      "secondName":{"type":"text"},
      "age":{"type":"integer"}
    }
  }
}

But I also find a that queries are sometimes written like this, with a _doc inside the mapping

PUT person
{
  "mappings": {
    "_doc":{
      "properties": {
        "firstName":{"type":"text"},
        "secondName":{"type":"text"},
        "age":{"type":"integer"}
      }
    }
  }
}

What does putting _doc do?

Does this answer your question? [what does \_doc represents in elasticsearch?](https://stackoverflow.com/questions/35747862/what-does-doc-represents-in-elasticsearch) — zsltg, Mar 28 '20 at 23:43
^ The above comment is a duplicate of this question. For which elasticsearch version you're talking about? — Harshit, Mar 29 '20 at 07:17

score 0 · Accepted Answer · answered Mar 29 '20 at 11:02

_doc in the second mapping is loosely related to how mappings used to be defined before 7.0.

Instead of _doc it'd include the type of your document. With that being said, the 2nd mapping would work prior to 7.0 w/o a problem, and >=7.0 if you specified include_type_name, i.e. PUT person?include_type_name=true.

More info here: https://www.elastic.co/blog/moving-from-types-to-typeless-apis-in-elasticsearch-7-0

The idea of all of this is that one index should only include one type of document, thereby rendering the type first redundant and later deprecated.

When creating an index, what is the point of '_doc' when defining the mapping of the index?

1 Answers1