Elasticsearch Clear Cache

Elasticsearch is a powerful search and analytics engine that is based on the Lucene library. It uses a distributed, scalable, and fault-tolerant architecture to provide high performance and reliability. As part of its functionality, Elasticsearch caches frequently accessed data to improve search and retrieval speeds. However, over time, the cache can consume a significant amount of memory, which can affect performance. Therefore, clearing the cache periodically is essential to maintain optimal performance.

In this guide, we'll look at how to clear cache in Elasticsearch.

Types of caches in Elasticsearch

Elasticsearch has several types of caches that it uses to store data:

• Field data cache: This cache stores the field data used in aggregations, sorting, and scripting.

• Filter cache: This cache stores the results of filter queries.

• Query cache: This cache stores the results of query requests.

• Request cache: This cache stores the results of search requests.

Clearing the cache in Elasticsearch

To clear the cache in Elasticsearch, you can use the Clear Cache API. There are different ways to use this API depending on the type of cache you want to clear.

Clearing the field data cache

To clear the field data cache, you can use the following command:

POST /<index>/_cache/clear?fielddata=true

Replace <index> with the name of the index for which you want to clear the cache. This command will clear the field data cache for all fields in the index.

Clearing the filter cache

To clear the filter cache, you can use the following command:

POST /_cache/clear?filter=true

This command will clear the filter cache for all indices.

Clearing the query cache

To clear the query cache, you can use the following command:

POST /_cache/clear?query=true

This command will clear the query cache for all indices.

Clearing the request cache

To clear the request cache, you can use the following command:

POST /_cache/clear?request=true

This command will clear the request cache for all indices.

Clearing multiple caches

To clear multiple caches at once, you can use the following command:

POST /_cache/clear?fielddata=true&filter=true&query=true&request=true

This command will clear all caches for all indices.

Conclusion

Regularly clearing the cache in Elasticsearch is important to maintain optimal performance. In this guide, we've looked at the different types of caches in Elasticsearch and how to clear them using the Clear Cache API. Use these commands to keep your Elasticsearch cluster running efficiently.