Re: [PROPOSAL] VACUUM Progress Checker.

On Fri, Jan 29, 2016 at 7:02 AM, Rahila Syed <rahilasyed90@gmail.com> wrote:
> Apart from these, as suggested in [1] , finer grained reporting from index
> vacuuming phase can provide better insight. Currently we report number of
> blocks processed once at the end of vacuuming of each index.
> IIUC, what was suggested in [1] was instrumenting lazy_tid_reaped with a
> counter to count number of index tuples processed so far as lazy_tid_reaped
> is called for every index tuple to see if it matches any of the dead tuple
> tids.
>
> So additional parameters for each index can be,
> scanned_index_tuples
> total_index_tuples (from pg_class.reltuples entry)

Let's report blocks, not tuples.  The reason is that
pg_class.reltuples is only an estimate and might be wildly wrong on
occasion, but the length of the relation in blocks can be known with
certainty.

But other than that I agree with this.  Fine-grained is key.  If it's
not fine grained, then people really won't be able to tell what's
going on when VACUUM doesn't finish in a timely fashion.  And the
whole point is we want to be able to know that.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company