| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | "Greg Rychlewski (LCL)" <Greg(dot)Rychlewski(at)loblaw(dot)ca> |
| Cc: | "David G(dot) Johnston" <david(dot)g(dot)johnston(at)gmail(dot)com>, Stephen Froehlich <s(dot)froehlich(at)cablelabs(dot)com>, "pgsql-novice(at)postgresql(dot)org" <pgsql-novice(at)postgresql(dot)org> |
| Subject: | Re: [EXT] Re: Does cancelling autovacuum make you lose all the work it did? |
| Date: | 2020-06-13 03:18:28 |
| Message-ID: | 798972.1592018308@sss.pgh.pa.us |
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| Lists: | pgsql-novice |
"Greg Rychlewski (LCL)" <Greg(dot)Rychlewski(at)loblaw(dot)ca> writes:
> Thanks for your reply. Regarding it being blocked, I don't think it is but I could be wrong. Both wait_event and wait_event_type are null. One thing I noticed though is that n_dead_tup in pg_stat_all_tables either stays the same or goes up. Should this be going down during the autovacuum?
No ... ongoing transactions could be creating new dead rows. IIRC,
a vacuum won't report its removal of dead rows to the stats collector
till the very end, so what I'd expect is a big drop when it finishes.
(I am not sure offhand what happens to those stats if you cancel the
vacuum partway through --- it might report nothing, causing the
stats to be way off until the next successful vacuum.)
regards, tom lane
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