Composite aggregation buckets not filtered as per the regexp query

Elastic Stack Elasticsearch
1

Hi there,
I have an aggregation query to get documents filtered by terms of a multi value filed and regexp matching. The buckets returned don't match the results returned as per regexp match criteria.

Note: Elasticsearch version 7.17

Below is sample code:

  1. Mapping
PUT /sales_index
{
  "settings": {
    "index": {
      "number_of_shards": "8",
      "refresh_interval": "180s"
    }
  },
  "mappings": {
    "dynamic": "false",
    "properties": {
      "id": {
        "type": "keyword"
      },
      "businessName": {
        "type": "keyword"
      },
      "category": {
        "type": "keyword"
      }
    }
  }
}
  1. Ingest data
POST /sales_index/_doc/_bulk
{"index":{"_id":1}}
{"businessName":["Asda","Tesco","Sainsbury"], "category": "store"}
{"index":{"_id":2}}
{"businessName":["Amazon","John Lewis","Asda"], "category": "online"}
{"index":{"_id":3}}
{"businessName":["BNQ","BNM"], "category": "store"}
  1. Query with composite aggregation
{
  "size": 0,
  "query": {
    "bool": {
      "must": [
        {
          "match_all": {
            "boost": 1.0
          }
        },
        {
          "bool": {
            "should": [
              {
                "terms": {
                  "category": [
                    "store",
                    "online"
                  ],
                  "boost": 1.0,
                  "_name": "filter-match-category-"
                }
              }
            ],
            "adjust_pure_negative": true,
            "boost": 1.0
          }
        },
        {
          "bool": {
            "should": [
              {
                "regexp": {
                  "businessName": {
                    "value": "As.*",
                    "flags_value": 255,
                    "case_insensitive": true,
                    "max_determinized_states": 10000,
                    "boost": 1.0
                  }
                }
              }
            ],
            "adjust_pure_negative": true,
            "boost": 1.0
          }
        }
      ],
      "adjust_pure_negative": true,
      "boost": 1.0
    }
  },
  "track_total_hits": -1,
  "aggregations": {
    "composite_facet": {
      "composite": {
        "size": 100,
        "sources": [
          {
            "businessName": {
              "terms": {
                "field": "businessName",
                "order": "asc"
              }
            }
          }
        ]
      }
    }
  }
}
  1. Query results
{
  "took" : 3,
  "timed_out" : false,
  "_shards" : {
    "total" : 8,
    "successful" : 8,
    "skipped" : 0,
    "failed" : 0
  },
  "hits" : {
    "max_score" : null,
    "hits" : [ ]
  },
  "aggregations" : {
    "composite_facet" : {
      "after_key" : {
        "businessName" : "Tesco"
      },
      "buckets" : [
        {
          "key" : {
            "businessName" : "Amazon"
          },
          "doc_count" : 1
        },
        {
          "key" : {
            "businessName" : "Asda"
          },
          "doc_count" : 2
        },
        {
          "key" : {
            "businessName" : "John Lewis"
          },
          "doc_count" : 1
        },
        {
          "key" : {
            "businessName" : "Sainsbury"
          },
          "doc_count" : 1
        },
        {
          "key" : {
            "businessName" : "Tesco"
          },
          "doc_count" : 1
        }
      ]
    }
  }
}
  1. Expected results:
"aggregations": {
    "composite_facet": {
      "buckets": [
        {
          "key": {
            "businessName": "Amazon"
          },
          "doc_count": 1
        },
        {
          "key": {
            "businessName": "Asda"
          },
          "doc_count": 2
        }
      ]
    }
  }

Please suggest how to optimise the query to get the Expected results that match as per regexp query

Thanks
Natraj