Index Nested object 6.2

[Varan]

Hi,

I've read that Elasticsearch's Nested object are usefull but aren't independant from their root index and
reindex the whole document if reindexed (https://www.elastic.co/blog/managing-relations-inside-elasticsearch).

But on the up to date documentation (6.2) it is said that "nested documents are indexed as separate documents" (https://www.elastic.co/guide/en/elasticsearch/reference/current/nested.html).

So I want to be sure, If I use this structure and reindex a Nested object, does it reindex the root index? Does it reindex the other nested object in the root index?

[Christian_Dahlqvist]

Yes, it does reindex the entire nested document, including root and all nested documents.

[Varan]

But let's say that in my Index "Personne" which got numerous field in which there is "name",
I have PUT two entity, Peter (_id : 1) and Alice (_id : 2).
There is also a nested object in Personne to keep their different mail adresses.
I have posted alice1@mail.com and to the _id2 and peter1@mail.com to the _id1.

Now let's say that I change the adress of alice so that she got a second adress as well.

POST Personne/_doc/2/_update
{
    "script" : {
        "lang": "painless",
        "source": "ctx._source.mail = params.mail",
        "params" : {
            "mail" : [
             {
             "mail1" : " alice1@mail.com",
            "mail2" : "alice2@mail.com"
              }
            ]
         }
      }
  }

What would be reindexed? Every field concerning Alice (her name, both of her mails)?
Everything inside Personne (including everything concerning Peter) ?

[Christian_Dahlqvist]

The entire document will be reindexed, the root as well as all nested documents. If I have a root document with a list of 5 nested documents and add another one, all 7 documents will be (re)indexed.

[Varan]

Thanks for your answers and sorry to bother you @Christian_Dahlqvist but I may haven't make myself comprehensible.
I don't mean that the root will be re-indexed as the mapping/schema will be changed.
I mean that if I add a nested object as in I add data (this person will have another mail adress). Will the index of the data of the person be reindexed/updated?

I want to add nested object causing as less operation as possible.

[Christian_Dahlqvist]

Yes, that is what I have tried to explain. Updating a nested document can be expensive.

[Varan]

Thanks for your answer.