How to find out stale alert rules

Prometheus server
1

Hi everyone ! I have some questions about alert rules.

  1. Are there any metrics about the total count of alert rules exposed by prometheus itself ?

  2. How can I find out the stale or useless alert rules and then delete them to reduce the computation activity of prometheus ? In our use case, the alert rules which have been always evaluated as “nodata” are considered as useless.

Thanks !