Follow-up from "Add partial index to improve mirrors update"

The following discussion from !57353 (merged) should be addressed:

• @ahegyi started a discussion: (+1 comment)

  One thing. We need to verify if the following index is needed or not:

      "index_mirror_data_on_next_execution_and_retry_count" btree (next_execution_timestamp, retry_count)

  We can do it as a follow up.

"w"e can periodically look up the index stats on PRD to see if this index is used at all.