Indexing of empty arrays affecting search results

[michael-jaxsta (Michael Stone)]

Hi all,

We are using Elasticsearch for searching content on our website which is primarily musician names.

The primary search field is "name" but we also have a number of secondary index fields included in the search such as an "aliases" field for matching the musician's stage name rather than their real name. Since a musician can have several aliases, this stored as an array e.g. Sean Combs has aliases Puff Daddy and P. Diddy.

Note that "aliases" is part of the "secondary_index_field" object.

A problem arises if a document is indexed where the "name" fields has a full stop e.g. "Portugal. The Man" and the aliases field is an empty array as per the example below.

{
  "_index": "jaxsta-20211124-231212",
  "_type": "_doc",
  "_id": "d0140c45-3122-4934-9d83-f4429c048069",
  "_version": 2,
  "_score": 0,
  "_source": {
    "jaxsta_uuid": "d0140c45-3122-4934-9d83-f4429c048069",
    "name": "Portugal. The Man",
    "secondary_index_field": {
      "entity_aliases": [],
      "identifiers": [
        "167649475",
        "4kI8Ie27vjvonwaB2ePh8T"
      ]
    }
  }
}

When I use the following search query, the document above is not returned.

GET jaxsta/_search
{
  "size": 2000,
  "query": {
    "function_score": {
      "query": {
        "multi_match": {
          "query": "Portugal. The Man",
          "fields": [
            "name",
            "secondary_index_field.entity_aliases",
            "secondary_index_field.identifiers"
          ],
          "type": "cross_fields"
        }
      }
    }
  }
}

But if I remove "secondary_index_field.entity_aliases" from the fields list, the correct document is returned in the search result.

In terms of mapping, we are using the following for these fields:

"name" : {
  "type" : "text",
  "fields" : {
	"keyword" : {
	  "type" : "keyword",
	  "ignore_above" : 256
	}
  }
},
"secondary_index_field" : {
  "properties" : {
	"entity_aliases" : {
	  "type" : "text",
	  "fields" : {
		"keyword" : {
		  "type" : "keyword",
		  "ignore_above" : 256
		}
	  }
	}
  }
}

Can anyone suggest what we are doing wrong?

Thanks,

Michael Stone