Explanation of what this does please

[malhal]

Sorry I couldn't understand what is going on with this example from the read-me. So there are 10k records. Are they all downloaded then filtered on the client? Or are they filtered on the server and only the current page is sent? If this is true does the client ever remove records not matching the filter from memory? Or does it keep them in case they another filter matches them again? Any additional information would be appreciated thanks.