Re: [PROPOSAL] VACUUM Progress Checker.

On Wed, Sep 23, 2015 at 12:24 AM, Syed, Rahila <Rahila(dot)Syed(at)nttdata(dot)com> wrote:
> Hello,
>
> Please find attached patch with bugs reported by Thom and Sawada-san solved.
>
>>* The progress of vacuum by autovacuum seems not to be displayed.
> The progress is stored in shared variables during autovacuum. I guess the reason they are not visible is that the entries are deleted as soon as the process exits.
> But the progress can be viewed while autovacuum worker is running.
>

Thank you for updating the patch.

I tested the latest version patch.
The followings are my review comments and questions.

* pg_stat_vacuum_progress should have the oid of relation being vacuumed.

When we run "VACUUM;", the all tables of current database will be vacuumed.
So pg_stat_vacuum_progress should have these oid in order to show
which table is vacuumed now.

* progress_message variable in PgBackendStatus is not used at all.
IIRC, progress_message variable is set the description of processing.

* The progress of VACUUM FULL seems wrong.
When I run VACUUM FULL for a table, I got following progress.

postgres(1)=# select * from pg_stat_vacuum_progress ;
-[ RECORD 1 ]-------+------
pid | 19190
total_pages | 1
scanned_pages | 1
total_heap_pages | 1
scanned_heap_pages | 1
total_index_pages |
scanned_index_pages |
percent_complete | 100

The table being vacuumed is 400MB, so it's not 1 page table.

* The vacuum by autovacuum is not displayed.
I tested about this by the executing the following queries in a row,
but the vacuum by autovacuum is not displayed,

postgres(1)=# select datname, pid, backend_start, query, state from
pg_stat_activity ;
datname | pid | backend_start |
query | state
----------+-------+-------------------------------+--------------------------------------------------------------------------+--------
postgres | 20123 | 2015-09-24 17:44:26.467021+09 | autovacuum: VACUUM
ANALYZE public.hoge | active
postgres | 19779 | 2015-09-24 17:42:31.57918+09 | select datname,
pid, backend_start, query, state from pg_stat_activity ; | active
(3 rows)

postgres(1)=# selecT * from pg_stat_vacuum_progress ;
pid | total_pages | scanned_pages | total_heap_pages |
scanned_heap_pages | total_index_pages | scanned_index_pages |
percent_complete
-----+-------------+---------------+------------------+--------------------+-------------------+---------------------+------------------
(0 rows)

postgres(1)=# select datname, pid, backend_start, query, state from
pg_stat_activity ;
datname | pid | backend_start |
query | state
----------+-------+-------------------------------+--------------------------------------------------------------------------+--------
postgres | 20123 | 2015-09-24 17:44:26.467021+09 | autovacuum: VACUUM
ANALYZE public.hoge | active
postgres | 19779 | 2015-09-24 17:42:31.57918+09 | select datname,
pid, backend_start, query, state from pg_stat_activity ; | active
(3 rows)

The vacuuming for hoge table took about 2min, but the progress of
vacuum is never displayed.
Could you check this on your environment?

Regards,

--
Masahiko Sawada