Elasticsearch Elasticsearch Not Null Query

By Opster Team

Updated: Jan 28, 2024

| 2 min read

Elasticsearch Not Null Query: Working with Missing and Existing Fields

When working with Elasticsearch, you may encounter situations where you need to filter documents based on the presence or absence of a specific field. This article will guide you through the process of creating not null queries in Elasticsearch, which will help you find documents with existing or missing fields.

Using the Exists Query

The exists query in Elasticsearch is used to filter documents that have a non-null value for a specified field. This query is useful when you want to retrieve documents where a particular field is not null.

Here’s an example of an exists query:

GET /_search
{
  "query": {
    "exists": {
      "field": "user"
    }
  }
}

In this example, the query will return all documents where the “user” field is not null.

Some of the reasons a field would be considered non-existent are if the indexed value is null or [], if the mapping of the field is set to “index”: false or simply because for some of the documents the field was not provided at index time.

Using the Bool Query with a Must Not clause to find documents with non-existent fields

The bool query allows you to combine multiple queries using logical operators like must, should, and must_not. To find documents where a specific field is null, you can use the must_not operator in combination with the exists query.

Here’s an example of a bool query with must_not:

GET /_search
{
  "query": {
    "bool": {
      "must_not": {
        "exists": {
          "field": "user"
        }
      }
    }
  }
}

In this example, the query will return all documents where the “user” field is null.

Combining Exists and Must Not Queries

You can also combine exists and must_not queries within a single bool query to filter documents based on multiple fields. For example, you might want to find documents where one field is not null and another field is null.

Here’s an example of combining exists and must_not queries:

GET /_search
{
  "query": {
    "bool": {
      "must": {
        "exists": {
          "field": "user"
        }
      },
      "must_not": {
        "exists": {
          "field": "email"
        }
      }
    }
  }
}

In this example, the query will return all documents where the “user” field is not null, and the “email” field is null.

Using Script Query for Complex Conditions

In some cases, you might need to check for more complex conditions, such as whether a field is not null and has a specific value. In these situations, you can use the script query to write custom logic using Painless, Elasticsearch’s scripting language.

Here’s an example of a script query:

GET /_search
{
  "query": {
    "bool": {
      "must": {
        "script": {
          "script": {
            "source": "doc['user'].size() > 0 && doc['user'].value == 'john'"
          }
        }
      }
    }
  }
}

In this example, the query will return all documents where the “user” field is not null and has the value “john”.

Conclusion

Elasticsearch provides various query types, such as exists, bool, and script queries, to help you filter documents based on the presence or absence of specific fields. By combining these queries, you can create powerful search conditions that meet your application’s requirements. Remember to consider the performance implications of using complex queries, and optimize your queries as needed to ensure efficient search operations.

Learn more about the exists query and bool query in these guides.