Elasticsearch alias type to reference multi fields

Question

I'm using Elasticsearch alias fields to rename some fields in my mapping without needing to reindex everything. Works great. Now I want to rename some multi fields as well, like this:

"message":{
  "type":"text",
  "fields":{
    "raw":{
      "type":"keyword"
    }
  }
}

That's an analyzed field named message and a keyword version named message.raw. I can make an alias for message like this:

"title":{
  "type":"alias",
  "path":"message"
}

But I cannot seem to figure out how to alias the message.raw field. I tried different things.

Suspected that this would work out of the box by just using title.raw and hoping that Elasticsearch would convert it to message.raw. Didn't work.
Specified raw as a field in title:

"title":{
    "type":"alias",
    "path":"message",
    "fields":{
        "raw":{
            "type":"alias",
            "path":"message.raw"
        }
    }
}

This generates the following error when updating the mapping: Mapping definition for [title] has unsupported parameters: [fields : {raw={type=alias, path=message.raw}}]

Specified title.raw as a new field:

"title":{
    "type":"alias",
    "path":"message"
},
"title.raw":{
    "type":"alias",
    "path":"message.raw"
}

This results in an error: Cannot merge a field alias mapping [title] with a mapping that is not for a field alias.

Is this supported somehow?

Val Val · Accepted Answer · 2019-08-16T07:14:47

Referencing multi-fields from an alias isn't supported. From the documentation: aliases cannot be used as the target of copy_to or in multi-fields.

You can create an alias for your multi-field without the dot. What you need to do is simply to name the title.raw field differently, e.g. title_raw:

"title":{
    "type":"alias",
    "path":"message"
},
"title_raw":{                    <--- change the name here
    "type":"alias",
    "path":"message.raw"
}

Then you can query message.raw the same way as title_raw.

Elasticsearch alias type to reference multi fields

1 Answers