Re: Tracking last scan time

On Tue, Aug 23, 2022 at 10:55:09AM +0100, Dave Page wrote:
> Often it is beneficial to review one's schema with a view to removing indexes
> (and sometimes tables) that are no longer required. It's very difficult to
> understand when that is the case by looking at the number of scans of a
> relation as, for example, an index may be used infrequently but may be critical
> in those times when it is used.
> 
> The attached patch against HEAD adds optional tracking of the last scan time
> for relations. It updates pg_stat_*_tables with new last_seq_scan and
> last_idx_scan columns, and pg_stat_*_indexes with a last_idx_scan column to
> help with this.

Would it be simpler to allow the sequential and index scan columns to be
cleared so you can look later to see if it is non-zero?  Should we allow
arbitrary clearing of stat columns?

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Indecision is a decision.  Inaction is an action.  Mark Batterson