Re: how to shrink pg_attribute table in some database

Can't, it generates huge IO spikes.

But....

Few hours ago i manually started vacuum verbose on pg_attribute, now its
finished and i have some outputs:

INFO: "pg_attribute": found 554728466 removable, 212058 nonremovable row
versions in 44550921 out of 49326696 pages DETAIL: 178215 dead row versions
cannot be removed yet. There were 53479 unused item pointers. 0 pages are
entirely empty. CPU 1097.53s/1949.50u sec elapsed 6337.86 sec. Query
returned successfully with no result in 01:47:3626 hours.

what do you think?

select count(*) on pg_attribute returns:
158340 rows

So as i understand vacuum full will create new pg_attribute and will wrote
those amount of "valid" rows, but still it will scan 300GB old table?
So estimate will be even ~same compering with regular vacuum?

2018-03-26 17:17 GMT+03:00 hubert depesz lubaczewski <depesz(at)depesz(dot)com>:

> On Mon, Mar 26, 2018 at 05:15:14PM +0300, Artem Tomyuk wrote:
> > For now pg_attribute bloated to 300GB in size, and we have only 260GB's
> of
> > free space on disk.
> > In normal situation pg_attribute takes 50mb in size for our DB...
> > Can we assume that if we will run vacuum full on pg_attribute it will
> take
> > additional 50MB on disk?
>
> You can estimate by doing:
>
> create table z as select * from pg_Attribute;
>
> and then checking size of z.
>
> bloat there suggests that you have huge churn in tables - like: create
> table, drop table, lots of times.
>
> Best regards,
>
> depesz
>
>