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Re: pg_class (system) table increasing size. - Mailing list pgsql-general

From dhaval jaiswal
Subject Re: pg_class (system) table increasing size.
Date
Msg-id MA1PR01MB00390F2F3D0A5473A7049AC0DFB50@MA1PR01MB0039.INDPRD01.PROD.OUTLOOK.COM
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In response to Re: pg_class (system) table increasing size.  (dhaval jaiswal <dhavallj@hotmail.com>)
Responses Re: pg_class (system) table increasing size.
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Adding to above.  Below are the outputs. 


 select count(*) from pg_stat_sys_tables  where n_tup_ins =0 ;
 count 
-------
   326
(1 row)

 select count(*) from pg_stat_sys_tables  where n_tup_upd =0 ;
 count 
-------
   358
(1 row)

 select count(*) from pg_stat_sys_tables  where n_tup_del =0 ;
 count 
-------
   344
(1 row)

 select count(*) from pg_stat_sys_tables  where n_tup_hot_upd =0 ;
 count 
-------
   358
(1 row)

 select count(*) from pg_stat_sys_tables  where n_live_tup =0 ;
 count 
-------
   326
(1 row)

 select count(*) from pg_stat_sys_tables  where n_dead_tup =0 ;
 count 
-------
   346
(1 row)




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From: pgsql-general-owner@postgresql.org <pgsql-general-owner@postgresql.org> on behalf of dhaval jaiswal <dhavallj@hotmail.com>
Sent: Monday, November 21, 2016 11:04 PM
To: Kevin Grittner; Alvaro Herrera
Cc: Adrian Klaver; David G. Johnston; pgsql-general@postgresql.org
Subject: Re: [GENERAL] pg_class (system) table increasing size.
 

I did check and found it was the bloated size of pg_class which was slowing down the performance. 

It got fixed by adding in routine maintenance task. Things are fine now. 


However, I want to know how come pg_class  (system table) get bloated/affected. 

What could be the possible ways, where i can look into. 


Due to business impact auto vacuum is off. 




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From: Kevin Grittner <kgrittn@gmail.com>
Sent: Friday, November 18, 2016 3:49 AM
To: Alvaro Herrera
Cc: dhaval jaiswal; Adrian Klaver; David G. Johnston; pgsql-general@postgresql.org
Subject: Re: [GENERAL] pg_class (system) table increasing size.
 
On Thu, Nov 17, 2016 at 3:16 PM, Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:

> Looks like you lost the stat data awhile ago (probably due to a server
> crash, or pg_stats_reset()) and it never got updated.  I suggest doing
> "ANALZYE pg_class" to create initial stats; that might prompt autovacuum
> to vacuum the table.  If the bloat is excessive, vacuuming might take a
> very long time, in which case perhaps consider VACUUM FULL (but be very
> aware of its consequences first).
>
> I think it's likely that this has happened to other catalogs as well, so
> check the pg_stat_sys_tables view for other entries with all zeroes in
> the n_tup_* columns.

+1

Also, you may want to review your autovacuum settings to make sure
they are aggressive enough.  You didn't describe you machine, your
workload, or your vacuum regimen, but if it's a large machine you
would probably need to raise autovacuum_vacuum_cost limit.  And if
autovacuum somehow got turned *off* you are likely to have all
kinds of problems with bloat, and may need to schedule some down
time to get it cleaned up.

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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