How to define dynamically / override the _default_ mapping in elasticsearch?

Question

Use case :

The index/indices will be built dynamically from a template, so that it will pick some custom settings (number of shards/replicas/ etc).

Generate dynamically the types and their mappings, enabling for them all the timestamp & ttl fields. Also define the same parent type for all types, except the parent type itself (I know its name).

{
   "template": "*",

   "settings": {
      ...................
   },

   "mappings": {

      "_default_": {
         "_parent": {
            "type": "ParentType"
         },
         "_timestamp": {
            "enabled": true,
            "store": true
         },
         "_ttl": {
            "enabled": true
         }
      }

   }
}

How could I disable the _parent field for the ParentType type itself ?

Jargote · Accepted Answer · 2016-09-05 17:27:50Z

1

After a little big of digging on the docs, I found out that you can override __default__ mappings using this work around.

{
   "mappings": {
      "_default_": {
         "_parent": {
             "type": "my_parent_type" # 1
         }
      },
      "my_parent_type": {
          "_parent": {
              "type": "_dummy" # 2
          }
      }
   }
}

1) This mapping configuration will be inherited by all your types including my_parent_typetype. Step 2 explains how to override your parent type _parent meta-field.

2) I found here https://www.elastic.co/guide/en/elasticsearch/reference/current/default-mapping.html that you can override any of the mappings from __default__ when you provide a specific mapping for the type in question.

In this case we are assigning the _parent mapping of my_parent_type to a _dummy parent type that does not have to exists in your index.

Note: ElasticSearch 2.x documentation states:

The _parent.type setting can only point to a type that doesn’t exist yet. This means that a type cannot become a parent type after it is has been created.

For this reason, you have to make sure you index first, a document that is not my_parent_type type, otherwise you'll get an at indexing time.

I hope this helps.

answered Sep 5, 2016 at 17:27

Jargote

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1 Comment

duc Over a year ago

But when index parent document you still require ?parent=, if not you will get error. Right now I am using a dummy value nil for _parent field, I don't know if it bad for performent or not.And sometime misleading too . Is there a way remove it ?

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