Скачать или смотреть Achieving Terms Aggregation on Nested Fields in Elasticsearch with Java SDK

Learn how to perform `terms aggregation` on nested fields in Elasticsearch using the latest Java SDK. We'll explore the solution to common pitfalls and provide guidance for effective usage.
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Achieving Terms Aggregation on Nested Fields in Elasticsearch with Java SDK

Elasticsearch is a powerful search engine that allows for complex queries, including aggregations on nested fields. However, developers often encounter challenges when dealing with nested fields, especially when using the Java SDK. In this guide, we'll address how to successfully execute a terms aggregation on a nested field using the Elasticsearch Java client library.

Understanding the Problem

Suppose you have an index mapping like this:

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In many cases, a common requirement is to aggregate data based on one of the nested fields, such as the sld field. However, users have reported that when they attempt to do this employing the co.elastic.clients:elasticsearch-java library, they find that the nested aggregation API is incomplete. Here's a snippet demonstrating the initial attempt:

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This code is not yielding the desired terms aggregation results.

The Solution

The issue arises from the version of the Java client library used. In this case, the 7.16.2 version does not support the retrieval of sub-aggregations effectively. To resolve the problem, upgrading your Java SDK to 7.17.18 or higher is crucial. This version introduces an aggregations method for the NestedAggregate class, allowing you to access sub-aggregations like so:

Step-by-Step Aggregation Execution

Define Sub-Aggregation for sld Field:
Create a terms aggregation for your nested field, specifying the domain.sld.

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Define Nested Aggregation:
Set up the nested aggregation and attach the previously defined sub-aggregation.

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Execute the Search Query:
Now, run the search query, ensuring that you include the nested aggregation.

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Access the Results:
After executing the query, you need to extract the results:

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Conclusion

By upgrading your Java SDK to version 7.17.18 or newer, you can effectively deal with nested aggregations in Elasticsearch. This enables you to perform terms aggregation on nested fields seamlessly. If you follow the steps outlined above, you'll be able to access your data as needed and utilize the power of Elasticsearch for complex queries.

Keep exploring, and remember that staying updated with the latest library versions can sometimes unlock new features that resolve existing issues.