Re: db size difference on primary and standby

On Thu, 2023-11-16 at 14:49 +0800, Eric Wong wrote:
> We discovered a disk usage difference between our primary and standby node.
>
> After much investigation, the disk usage difference is caused by some
> extra files within the database directory 16432.  The extra files are
> only found on the standby node, not present on the primary.
>
> In the data directory ("15/data/base/16432"), the extra files do not
> seem to belong to any table. Normally, the files correspond to the
> column "relfilenode" in the "pg_class" system table; however, when we
> compare the entries in that column with the file names, around 600 of
> the files do not have a corresponding entry in the "pg_class" table.
> The same applies to the files in the "san" tablespace
> ("pg_tblspc/san/PG_15_202209061/16432").
>
> Has anyone seen this behavior before?  Also, we also want to know if
> it is safe to remove all those extra files that do not have an entry
> in the "pg_class" table?

If the files only exist on the standby, you can safely remove them.
Be careful, however: if you make a mistake, you'll corrupt your database.

Orphaned files like that can be left behind after a database crash.
Did you experience crashes on the standby?

Yours,
Laurenz Albe