Elasticsearch highlighting: "multi-match" query on custom "_all"-fields created with "copy_to"

Question

(Elasticsearch 5.2.2)

I'm having some trouble getting highlighting to work correctly. My mapping has 2 custom created _all-fields myall1 and myall2 that are created via copy_to:

"mytype": {
  "_all": {
    "enabled": false
  },
  "properties": {
    "myall": {
        "type": "text",
        "analyzer": "standard",
        "store": true
    },
    "myall2": {
        "type": "text",
        "analyzer": "standard",
        "store": true
    },
    "field1": {
        "type": "text",
        "copy_to": "myall1",
        "analyzer": "keyword"
    },
    "field2": {
        "type": "text",
        "copy_to": "myall2",
        "analyzer": "keyword"
    }
}

A document would look like this:

{
  "field1": "example text",
  "field2": "another text"
}

Now I'm running a multi_match-query that boosts myall1 by 3:

POST /myindex/mytype/_search
{
  "query": {
    "bool": {
      "must": {
        "multi_match": {
          "fields": ["myall1^3", "myall2"],
          "type": "cross_fields",
          "query": "example text",
          "operator": "and"
        }
      }
    }
  }
}

This works quite well. The problem is that I cannot highlight the original source-fields in the result. I'm adding the following to the query the same way it is done in the ES-docs "_all example":

  ,
  "highlight": {
    "pre_tags": ["<span class='highlight'>"],
    "post_tags": ["</span>"],
    "fields": {
      "*": {"require_field_match": false}
    }
  }

This gives me only the highlighting in "myall1" and "myall2", NOT in the original fields "field1" and "field2".

If I do something similar by using the _all-field, everything works as expected. The main difference is: I'm using multi_match while the examples use query_string. Playing with "store":true and "analyzer":"standard" didn't help.

As my actual document uses nested-objects that must be searchable, I might not be able to do a completely different query-approach.

Is this by design or am I missing something? Using the "_all"-field instead would not allow me to boost results the way I'm trying to implement it.

Tobias81 Tobias81 · Accepted Answer · 2017-07-03T16:46:27

Fixed it. Seems that highlighting of the original fields requires them to use the same analyzer as the "copy-to" target field does. Otherwise they simply won't show up.

I was using "analyzer":"keyword" before as I did not plan to do actual queries on those fields. Now everything works as expected.

Elasticsearch highlighting: "multi-match" query on custom "_all"-fields created with "copy_to"

1 Answers