Re: Why doesn't autovacuum/analyze run in due time after calling pg_stat_reset?

On 8/21/23 00:15, Adrian Klaver wrote:
> On 8/20/23 12:10, Rihad wrote:
>> On 8/20/23 20:22, Adrian Klaver wrote:
>>> On 8/18/23 22:35, Rihad wrote:
>>>> On 8/17/23 13:01, rihad wrote:
>>>>>
>>>>> Hi, all. After calling pg_stat_reset all statistics used by
>>>>> autovacuum got zeroed, and started accumulating from scratch. Some
>>>>> tables get acted upon properly, some don't.
>>>>>
>>>>>
>>>> Self-replying: yup, it seems there's an arbitrary limit of 100K of
>>>> n_live_tup after which autovac/analyze kicks in, or it seems so.
>>>
>>> To know rather then guess read:
>>>
>>> https://www.postgresql.org/docs/current/routine-vacuuming.html#AUTOVACUUM
>>>
>>
>>
>> Sure, I read it before asking.
>>
>> Taking the first table in the list as an example:
>>
>>
>>          relname          | n_live_tup | n_dead_tup |   left   |
>> n_mod_since_analyze |  left
>> --------------------------+------------+------------+----------+---------------------+--------
>>
>> fooooooooooo             |      32781 |     240663 |  -234057 |
>>               513265 | -509937
>>
>>
>> n_dead_tup (not the actual value, but some time after calling
>> pg_stat_reset) is much larger than 20% of n_live_tup 32781, and
>> n_mod_since_analyze is much larger than 10% of it.
>>
>> Yet it is kept unvacuumed and unanalyzed for a long time.
>>
>> autovacuum_(vacuum|analyze)_threshold is 50.
>>
>> What am I missing?
>
> Hard to say without seeing the actual settings in postgresql.conf that
> match:
>
> https://www.postgresql.org/docs/current/runtime-config-autovacuum.html#GUC-AUTOVACUUM-VACUUM-SCALE-FACTOR
>
>
>
> Most importantly:
>
> autovacuum
>
> and
>
> track_counts
>
> https://www.postgresql.org/docs/current/runtime-config-statistics.html#GUC-TRACK-COUNTS
>
>

They are both on and set as per default. Autovac/analyze continue
running on some tables after pg_stat_reset. Just not on all of them,
even thought they should judging by live/dead tuples calculation.

foo=> show track_counts;
track_counts
--------------
on
(1 row)

foo=> show autovacuum;
autovacuum
------------
on
(1 row)

>>
>>
>>>
>>>>
>>>> There are still many tables waiting for their turn, which is long due.
>>>>
>>>> Although there are some tables having only 60-70 (not 60-70K)
>>>> n_live_tup that have had autovacuum run on them. Weird.
>>>>
>>>>
>>>>
>>>
>>>
>>
>