Is it possible to extract the stored value of a keyword field when _source is disabled in Elasticsea-CodePudding

I have the following index:

    {
      "articles_2022" : {
        "mappings" : {
          "_source" : {
            "enabled" : false
          },
          "properties" : {
            "content" : {
              "type" : "text",
              "norms" : false
            },
            "date" : {
              "type" : "date"
            },
            "feed_canonical" : {
              "type" : "boolean"
            },
            "feed_id" : {
              "type" : "integer"
            },
            "feed_subscribers" : {
              "type" : "integer"
            },
            "language" : {
              "type" : "keyword",
              "doc_values" : false
            },
            "title" : {
              "type" : "text",
              "norms" : false
            },
            "url" : {
              "type" : "keyword",
              "doc_values" : false
            }
          }
        }
      }
    }

I have a very specific one-time need and I want to extract the stored values from the url field for all documents. Is this possible with Elasticsearch 7? Thanks!

CodePudding user response：

Since in your index mapping, you have defined url field as of keyword type and have "doc_values": false. Therefore you cannot perform terms aggregation on this.

As far as I can understand your question, you only need to get the value of the of the url field in several documents. For that you can use exists query

Adding a working example

Index Mapping:

PUT idx1
{
  "mappings": {
    "properties": {
      "url": {
        "type": "keyword",
        "doc_values": false
      }
    }
  }
}

Index Data:

POST idx1/_doc/1
{
  "url":"www.google.com"
}

POST idx1/_doc/2
{
  "url":"www.youtube.com"
}

Search Query:

POST idx1/_search
{
  "_source": [
    "url"
  ],
  "query": {
    "exists": {
      "field": "url"
    }
  }
}

Search Response:

"hits" : [
      {
        "_index" : "idx1",
        "_type" : "_doc",
        "_id" : "1",
        "_score" : 1.0,
        "_source" : {
          "url" : "www.google.com"
        }
      },
      {
        "_index" : "idx1",
        "_type" : "_doc",
        "_id" : "2",
        "_score" : 1.0,
        "_source" : {
          "url" : "www.youtube.com"
        }
      }
    ]

CodePudding user response：

As your

"_source" : { "enabled" : false }

You can add mapping "store:true" for the field that you want to extract value of.

PUT indexExample2
{
  "mappings": {
    "_source": {
      "enabled": false
    }, 
    "properties": {
      "url": {
        "type": "keyword",
        "doc_values": false,
        "store": true
      }
    }
  }
}

Now once you index data, @ESCoder Thanks for example.

POST indexExample2/_doc/1
{
  "url":"www.google.com"
}

POST indexExample2/_doc/2
{
  "url":"www.youtube.com"
}

You can extract only the stored field in your search queries, even if _source is disabled.

POST indexExample2/_search
{
  "query": {
    "exists": {
      "field": "url"
    }
  },
  "stored_fields": ["url"]
}

This will o/p as:

"hits" : [
  {
    "_index" : "indexExample2",
    "_type" : "_doc",
    "_id" : "1",
    "_score" : 1.0,
    "fields" : {
      "url" : [
        "www.google.com"
      ]
    }
  },
  {
    "_index" : "indexExample2",
    "_type" : "_doc",
    "_id" : "2",
    "_score" : 1.0,
    "fields" : {
      "url" : [
        "www.youtube.com"
      ]
    }
  }
]