If the SQL server 2008 r2 is not connected to the SharePoint 2013 farm , it will not affect the sharepoint 2013 farm when you uninstall the SQL server 2008 r2 from the SharePoint server.
You could uninstall the SQL server 2008 r2 from the SharePoint server as usual.
Then you could follow the steps in the articles below to uninstall SQL server 2008 r2.
Reset the entire search index? No. Reindex a specific site via the button in site settings? Shouldn't cause any issues.
Also, check the site setting: "allow this site to appear in search results". And, it wouldn't hurt to verify with IT that the account that is used for the crawl has access to the site.
You can go to site settings->Site collection features->deactivate "Limited-access user permission lockdown mode" feature.
Of course, for other pages, the users need permission to access. If the user wants to access the relevant page, I suggest you give relevant permission to a user account and login with this account.
Please do the following steps as below to troubleshoot this issue:
Restart the "SharePoint Server Search 15" service.
Make sure there is enough memory and disk space.
Reconfiguring Content Processing Component, follow the steps as below:
SharePoint 2013 : How to repair a ...