Обсуждение: DB size value different than "/data" dir size

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DB size value different than "/data" dir size

От
"Ghiurea, Isabella"
Дата:

Hi List,

I am running   PGSQL version 12.3   cfg   master-slave  with  streaming replication and I am facing a issue in the present active Pg db. 

The database size reported from  the following : pg_size_pretty() or pg_database_size() or sum all of db  objects is  grater than the  sum size of  all directories/files reported  under /var/lib/pgsql/data1/tbl_space_name/PG_12,,,xxx/ .  ( db data tablespace)


[ Mention in standby PG db the size matches the /data  sum file size and also  matches with the size reported in Pg active for  pg_size_pretty() or pg_database_size ]


What can be the issue?

thank you !

Isabella

Re: DB size value different than "/data" dir size

От
Ron Johnson
Дата:
On Fri, Aug 8, 2025 at 7:17 PM Ghiurea, Isabella <Isabella.Ghiurea@nrc-cnrc.gc.ca> wrote:

Hi List,

I am running   PGSQL version 12.3 


Ignoring the fact that PG 12 is nine months EOL, 12.3 is missing a _lot_ of bug fixes.  You should be on 12.22.
 

 cfg   master-slave  with  streaming replication and I am facing a issue in the present active Pg db. 

The database size reported from  the following : pg_size_pretty() or pg_database_size() or sum all of db  objects is  grater than the  sum size of  all directories/files reported  under /var/lib/pgsql/data1/tbl_space_name/PG_12,,,xxx/ .  ( db data tablespace)


[ Mention in standby PG db the size matches the /data  sum file size and also  matches with the size reported in Pg active for  pg_size_pretty() or pg_database_size ]


What can be the issue?


What's in $PGDATA?

--
Death to <Redacted>, and butter sauce.
Don't boil me, I'm still alive.
<Redacted> lobster!

Re: DB size value different than "/data" dir size

От
Laurenz Albe
Дата:
On Fri, 2025-08-08 at 23:17 +0000, Ghiurea, Isabella wrote:
> I am running   PGSQL version 12.3   cfg   master-slave  with  streaming replication
> and I am facing a issue in the present active Pg db. 
> The database size reported from  the following : pg_size_pretty() or pg_database_size()
> or sum all of db  objects is  grater than the  sum size of  all directories/files
> reported  under /var/lib/pgsql/data1/tbl_space_name/PG_12,,,xxx/ .  ( db data tablespace)

Perhaps some part of the data is in a different tablespace, maybe pg_default.

Yours,
Laurenz Albe



Re: Re: DB size value different than "/data" dir size

От
"Ghiurea, Isabella"
Дата:

I believe this is related to VACUUM FULL behavior in a streaming replication cfg ,   for the standby server the space is not been reclaimed , But the sieze of db reported with pg_pretty_db_size is identical on both db size but is  not the actual sum of /var/lib/pgsql/data1 files +dir size on the active PG were vacuum full reclaim the space.                                                                                                                                                                Is this a normal behavior  in PG with reporting incorrect db size if vacuum full has not reclaim the OS disk space on both server?


From: Laurenz Albe <laurenz.albe@cybertec.at>
Sent: Sunday, August 10, 2025 12:27:31 PM
To: Ghiurea, Isabella; pgsql-admin@postgresql.org
Subject: EXT: Re: DB size value different than "/data" dir size
 
***Attention*** This email originated from outside of the NRC. ***Attention*** Ce courriel provient de l'extérieur du CNRC.
On Fri, 2025-08-08 at 23:17 +0000, Ghiurea, Isabella wrote:
> I am running   PGSQL version 12.3   cfg   master-slave  with  streaming replication
> and I am facing a issue in the present active Pg db. 
> The database size reported from  the following : pg_size_pretty() or pg_database_size()
> or sum all of db  objects is  grater than the  sum size of  all directories/files
> reported  under /var/lib/pgsql/data1/tbl_space_name/PG_12,,,xxx/ .  ( db data tablespace)

Perhaps some part of the data is in a different tablespace, maybe pg_default.

Yours,
Laurenz Albe

Re: Re: DB size value different than "/data" dir size

От
Laurenz Albe
Дата:
On Mon, 2025-08-11 at 14:13 +0000, Ghiurea, Isabella wrote:
> I believe this is related to VACUUM FULL behavior in a streaming replication cfg ,
> for the standby server the space is not been reclaimed , But the sieze of db reported
> with pg_pretty_db_size is identical on both db size but is  not the actual sum of
> /var/lib/pgsql/data1 files +dir size on the active PG were vacuum full reclaim the space.
>
> Is this a normal behavior  in PG with reporting incorrect db size if vacuum full has
> not reclaim the OS disk space on both server?

VACUUM (FULL) will also reclaim the size on the standby.
There can be some delay in the case of a replication conflict.

Yours,
Laurenz Albe