Re: Diagnosing a massive toast file

As a follow up, n_dead_tup from pg_stat_sys_tables for this TOAST table is 7447444, live tuples, 623982, and tup_del 20823469. vacuum_count is 0.

Why can't I free those rows up?

On Mon, Aug 5, 2019 at 10:00 AM Wells Oliver <wells.oliver@gmail.com> wrote:

Appreciate it, guys. I understand it being large isn't itself a problem, but relative to history and the lack of real changes, it's just strange and I'd like to better understand what is going on...

I tracked it down to a specific table, and then doing a VACUUM FULL ANALYZE on that table yields: 108765 dead row versions cannot be removed yet.

Which strikes me as odd. Any reading I can do to better understand why so many (relative to the overall table size) dead rows cannot be removed?

On Mon, Aug 5, 2019 at 9:49 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:

Wells Oliver <wells.oliver@gmail.com> writes:
> Yeah, trying to figure out what actual table is clearly in need of a vacuum
> b/c of the size of that toast table.

Something like

select relname from pg_class
where reltoastrelid = 'pg_toast.pg_toast_NNN'::regclass;

(or, if you have potential duplicate relnames, select oid::regclass ...)

The mere fact that it's big does not indicate a problem, though.

                        regards, tom lane

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Wells Oliver
wells.oliver@gmail.com

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Wells Oliver
wells.oliver@gmail.com