How to update index mapping with dynamic as strict in future? - elasticsearch

Question

I am new to elastic search. I have an index named users, which has a lot of fields I know. But a few more fields can be added in the future.
So when defining my mapping, I want to include the fields that I know currently with dynamic "strict", but in the future, if I want to add the new field, how will update the new mapping and if I do it, will I have to reindex everything.
I found in the ES documents that mappings are applied only during index creation time. So I am a little confused here, what's the right way to approach this.

Answer 1

You can always update the mapping in future, even after keeping it strict using the put mapping api. You'll not require existing data to be re-indexed unless you want the newly added field have some value for the older documents which were added before updating the mapping with the new field.
Lets assume you already have an index test with one field say field1 of type keyword. Now in future you have a requirement to add new field say field2 of integer type. You can do so by the put mapping api as below,
PUT test/_mapping
{
"properties": {
"field2": {
"type": "integer"
}
}
}
After executing the above if you check the mapping using
GET test/_mapping
You can see the new field as well in the response,
{
"test" : {
"mappings" : {
"dynamic" : "strict",
"properties" : {
"field1" : {
"type" : "keyword"
},
"field2" : {
"type" : "integer"
}
}
}
}
}

Answer 2

Inner objects inherit the dynamic setting from their parent object or from the mapping type. In the following example, dynamic mapping is disabled at the type level, so no new top-level fields will be added dynamically.
However, the user.social_networks object enables dynamic mapping, so you can add fields to this inner object.
https://www.elastic.co/guide/en/elasticsearch/reference/current/dynamic.html
PUT my-index-000001
{
"mappings": {
"dynamic": false,
"properties": {
"user": {
"properties": {
"name": {
"type": "text"
},
"social_networks": {
"dynamic": true,
"properties": {}
}
}
}
}
}
}