How to Clear the Cache In Solr?

To clear the cache in Solr, you can use the Core Admin API or the Solr Admin Console. First, identify the specific cache that you want to clear, whether it's the query result cache, filter cache, document cache, or any other cache.

If you choose to use the Core Admin API, you can send a POST request to the appropriate URL with the action "cache" and the name of the cache that you want to clear.

If you prefer to use the Solr Admin Console, you can navigate to the Core Admin page, select the core that you want to clear the cache for, and then click on the "Clear Cache" button.

After successfully clearing the cache, you should see improvements in the performance of your Solr instance as it will need to fetch fresh data instead of relying on cached information.

How to check the current cache size in Solr?

To check the current cache size in Solr, you can access the Solr Admin UI and navigate to the "Core Admin" page for the specific Solr core you want to check.

1. Go to the Solr Admin UI by visiting http://localhost:8983/solr (or the appropriate URL where your Solr instance is running).
2. Click on the core name for which you want to check the cache size.
3. Navigate to the "Core Admin" page for that core.
4. Look for the "Cache" section on the Core Admin page. This section should display information about the various caches used by the core, including their current size.

Alternatively, you can also use Solr's REST API to check the current cache size. You can make a GET request to the following endpoint:

http://localhost:8983/solr/{core_name}/config/params

This will return a JSON response containing information about the cache configuration for the specified core, including the current cache size. You can look for the "filterCache" and/or "queryResultCache" sections in the response to find the current cache size.

How to clear the filter cache in Solr?

To clear the filter cache in Solr, you can follow these steps:

1. Access the Solr Admin UI by navigating to http://localhost:8983/solr (or your Solr URL if different).
2. Go to the Core Selector and select the core where you want to clear the filter cache.
3. Click on the "Query" option in the left-hand menu.
4. In the "Query Parameters" section, locate the "filterCache" parameter.
5. Click on the "Clear" button next to the "filterCache" parameter.
6. Confirm the action when prompted.

After following these steps, the filter cache for the selected Solr core should be cleared. This will result in a clean slate for filter cache usage, and Solr will start building up the cache again as queries are executed.

What is the difference between clearing the document cache and the update cache in Solr?

Clearing the document cache in Solr removes all cached documents from memory, which can improve query performance by freeing up memory and speeding up the retrieval of data from disk. On the other hand, updating the cache in Solr involves refreshing the cache with the latest information and documents from the index, which can improve query performance by ensuring that the cache is up to date with the most recent data. In summary, clearing the document cache removes all cached documents from memory, while updating the cache refreshes the cache with the latest information from the index.