How to Clear the Cache In Solr?

To clear the cache in Solr, you can use the following steps:

1. Stop the Solr server to ensure no changes are being made to the cache while it is being cleared.
2. Delete the contents of the cache directory in the Solr instance.
3. Restart the Solr server to reload the data and recreate the cache.
4. You can also configure the cache size or TTL (time to live) settings in the Solr configuration file to manage cache behavior effectively.

What is the difference between query cache and filter cache in Solr?

Query cache and filter cache are both used in Solr to improve search performance by caching results of frequently executed queries or filters. However, there are some key differences between the two:

1. Query cache: The query cache stores the entire result set of a query, including the ranking of documents. When a query is executed, Solr checks the query cache to see if the exact same query has been executed before with the same parameters. If so, it returns the cached result instead of re-executing the query. This can significantly improve performance for repeated queries with the same parameters.
2. Filter cache: The filter cache stores the results of filters applied to queries, such as range queries or term queries. When a filter is applied to a query, Solr caches the result of that filter for future queries. This can improve performance for queries that include the same filter multiple times.

In summary, the main difference between query cache and filter cache is the type of data that is cached - query cache stores entire result sets of queries, while filter cache stores results of filters applied to queries. Both types of caches can be useful in improving search performance, but their usage depends on the specific requirements of the application.

What is cache warming in Solr?

Cache warming in Solr is the process of pre-loading and populating the caches in a Solr instance with frequently accessed data before the system is put into production. This helps to improve the overall performance of the Solr server by reducing the latency of search queries. Cache warming can be done by running specific queries or performing bulk operations to preload the caches with relevant data, ensuring that the system is primed and ready to serve search requests efficiently.

How to refresh cache in Solr?

To refresh the cache in Solr, you can use the following steps:

1. Open the Solr admin console in your browser.
2. Navigate to the Core Admin section.
3. Find the core for which you want to refresh the cache and click on it.
4. In the Core admin, find the "Query" tab and click on it.
5. In the Query tab, you will see an option for "Query Settings".
6. Under the Query Settings, you will find an option called "Clear Query Cache". Click on this option to refresh the cache in Solr for that core.

Alternatively, you can also use the Solr API to clear the cache. You can send a POST request to the following endpoint to clear the cache for a specific core:

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http://localhost:8983/solr/<core_name>/update?commit=true

Replace <core_name> with the name of the core for which you want to clear the cache.

By following these steps, you can refresh the cache in Solr and ensure that your queries are up to date with the latest data.

What are the different types of cache in Solr?

1. Document Cache: Stores parsed documents in memory, reducing the need to re-parse the same document multiple times during query processing.
2. Field Value Cache: Stores field values of documents in memory, allowing for faster access to frequently accessed field values during query processing.
3. Query Result Cache: Stores the results of frequently executed queries in memory, allowing for faster retrieval of results without executing the query again.
4. Filter Cache: Stores the results of filters applied to queries in memory, allowing for faster filtering of documents during query processing.
5. Filter Query Cache: Stores the results of filter queries in memory, allowing for faster access to precomputed filter query results during query processing.
6. Query Cache: Stores the results of frequently executed queries in memory, allowing for faster retrieval of results without executing the query again.
7. Update Handler Cache: Stores information related to document updates in memory, allowing for faster access to recent updates during indexing operations.

How to check cache hit ratio in Solr?

To check the cache hit ratio in Solr, you can use the Solr admin UI or run a query using the Solr API. Here's how you can do it:

1. Using Solr Admin UI:

• Open your web browser and navigate to the Solr admin UI.
• Click on the "Core Selector" dropdown menu and select the core you want to check the cache hit ratio for.
• Click on the "Core" tab in the left-hand menu.
• In the "Statistics" section, you will find information about cache hit ratio.

1. Using Solr API:

• Open a web browser and navigate to the following URL: http://:8983/solr//select?q=:&stats=true
• Replace "" with the hostname or IP address of your Solr server and "" with the name of the core you want to check.
• This query will return statistics including cache hit ratio. Look for the "stats" section in the response JSON to find the cache hit ratio.

By using either of these methods, you can easily check the cache hit ratio in Solr.