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Re: Support reset of Shared objects statistics in "pg_stat_reset" function - Mailing list pgsql-hackers

From Himanshu Upadhyaya
Subject Re: Support reset of Shared objects statistics in "pg_stat_reset" function
Date
Msg-id CAPF61jCSTC_RLKnG6j-XNOmMcy_g+Z73iDdQAQLS_08RW-h2mg@mail.gmail.com
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In response to Support reset of Shared objects statistics in "pg_stat_reset" function  (Sadhuprasad Patro <b.sadhu@gmail.com>)
Responses Re: Support reset of Shared objects statistics in "pg_stat_reset" function
Re: Support reset of Shared objects statistics in "pg_stat_reset" function
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Hi Sadhu,


> The call to “pg_stat_reset“ does reset all the statistics data for
> tables belonging to the current database but does not take care of
> shared tables e.g pg_attribute.

pg_attribute is not a shared catalog, is the mentioned scenario is also applicable for few others tables?

I have just tried it with-out your patch:

postgres=# SELECT * FROM pg_statio_all_tables  where relid=1249;
 relid | schemaname |   relname    | heap_blks_read | heap_blks_hit | idx_blks_read | idx_blks_hit | toast_blks_read | toast_blks_hit | tidx_blks_read | tidx_blks_hit
-------+------------+--------------+----------------+---------------+---------------+--------------+-----------------+----------------+----------------+---------------
  1249 | pg_catalog | pg_attribute |             29 |           522 |             8 |          673 |                 |                |                |              
(1 row)

postgres=# select pg_stat_reset();
 pg_stat_reset
---------------
 
(1 row)

postgres=# SELECT * FROM pg_statio_all_tables  where relid=1249;
 relid | schemaname |   relname    | heap_blks_read | heap_blks_hit | idx_blks_read | idx_blks_hit | toast_blks_read | toast_blks_hit | tidx_blks_read | tidx_blks_hit
-------+------------+--------------+----------------+---------------+---------------+--------------+-----------------+----------------+----------------+---------------
  1249 | pg_catalog | pg_attribute |              0 |             0 |             0 |            0 |                 |                |                |             


We are able to reset the stats of pg_attibute without your patch.

Thanks,
Himanshu

On Fri, Aug 6, 2021 at 1:56 PM Sadhuprasad Patro <b.sadhu@gmail.com> wrote:
Hi,

The call to “pg_stat_reset“ does reset all the statistics data for
tables belonging to the current database but does not take care of
shared tables e.g pg_attribute. Similarly to reset the statistics at
table level, the call to “pg_stat_reset_single_table_counters“ does
not take care of shared tables.

When we reset all the statistics using the call “pg_stat_reset”, the
postgres process internally makes calls to “
pgstat_recv_resetcounter“, which resets the statistics of all the
tables of the current database. But not resetting the statistics of
shared objects using database ID as 'InvalidOid'.

The same fix is made in the internal function
“pgstat_recv_resetsinglecounter“ to reset the statistics for the
shared table for the call "pg_stat_reset_single_table_counters".

--
thank u
SADHU PRASAD
EnterpriseDB: http://www.enterprisedb.com

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