Re: vacuum process running for more than 2 days, still in scanning heap phase

On 2025-Nov-12, Sbob wrote:

> We have a vacuum process that has been running for 2 days, the table
> is 12GB in total size and vacuum_cost_delay is at 0

Is it autovacuum? Because if so, the autovacuum_vacuum_cost_delay
setting would be used instead of this one. Also check the table config
(\d+) in case there are autovacuum settings there, which could make
vacuum slower on this particular table.

What PG version again?

> heap_blks_total    | 571437
> heap_blks_scanned  | 344577
> heap_blks_vacuumed | 0
> index_vacuum_count | 0
> max_dead_tuples    | 155388267
> num_dead_tuples    | 199013

Yeah, this seems really slow. Maybe have a look at the wait events in
pg_stat_activity to see if you can figure out what is holding it back.

> We actually tried a pg_terminate_backend on it and it does not die

Hmm, maybe there's something going wrong with it. I've seen corrupted
btree indexes make a vacuum go into infinite loops because of loops in
the index structure. I would take a few backtraces with gdb or such.
Maybe if an index is corrupt in that way, it would also explain why it
doesn't interrupt.

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