Aggregation on lowercase keycord

OpenSearch
1

Hi,

i have the field “currency” with the following mapping configuration:

  "currency" : {
    "type" : "keyword",
    "normalizer": "lowercase"
  },

I need to aggregate the currency value, but case sensitive.

When i use the following query, the aggregation is case INsensitive:

GET index/_search
{
  "aggs": {
    "date": {
      "date_histogram": {
        "field": "created_at",
        "interval": "day"
      },
      "aggs": {
        "string": {
          "terms": {
	    "size": 5000,
	    "script": {
	      "source": "(doc['currency'].size() == 0 ? '' : doc['currency'].value)",
	      "lang": "painless"
	    }
          }
        }
      }
    }
  }
}

Using params._source['currency'] instead of doc['currency'].value, the query is VERY SLOW.

What’s the best way to solve this issue?