How can I sort Elasticsearch result based on nested field with keyword datatype?

Question

This is a snippet of my mapping:

    "products": {
    "properties": {
        "availability_date": {
            "type": "date"
        },
        "banner": {
            "properties": {
                "id": {
                    "type": "long"
                },
                "copyright": {
                    "type": "keyword"
                },
                "url": {
                    "type": "keyword"
                }
            }
        },
        "categories": {
            "type": "nested",
            "properties": {
                "id": {
                    "type": "long"
                },
                "category_type": {
                    "type": "keyword"
                },
                "name": {
                    "type": "text"
                }
            }
        }
    }

I want to sort my search result based on "categories.name"

I try to hit it with:

"sort":[
  {
     "categories.name":{
        "order":"asc",
        "nested_path":"categories"
     }
  }
],

But that does not work and return a message:

"Fielddata is disabled on text fields by default. Set fielddata=true on [categories.name] in order to load fielddata in memory by uninverting the inverted index. Note that this can however use significant memory. Alternatively use a keyword field instead."

So then I change the mapping to:

"products": {
"properties": {
    "availability_date": {
        "type": "date"
    },
    "banner": {
        "properties": {
            "id": {
                "type": "long"
            },
            "copyright": {
                "type": "keyword"
            },
            "url": {
                "type": "keyword"
            }
        }
    },
    "categories": {
        "type": "nested",
        "properties": {
            "id": {
                "type": "long"
            },
            "category_type": {
                "type": "keyword"
            },
            "name": {
                "type": "text",
                "fields": {
                    "keyword": {
                        "type": "keyword",
                        "normalizer": "sort_normalizer"
                    }
                }
            }
        }
    }
}

How do I do the sorting now? I tried this:

"sort":[
  {
     "categories.name.keyword":{
        "order":"asc",
        "nested_path":"categories.name"
     }
  }
],

That does not work with reason:

"[nested] failed to find nested object under path [categories.name]"

Some other map work but giving me unsorted result

Answer 1

You should use

 "sort":[
      {
         "categories.name.keyword":{
            "order":"asc",
            "nested_path":"categories"
         }
      }
    ],

since the nested field is still categories and not categories.name