Re: FSM corruption leading to errors

On Thu, Oct 20, 2016 at 2:50 PM, Pavan Deolasee
<pavan.deolasee@gmail.com> wrote:
> Actually, if we could add an API which can truncate FSM to the given heap
> block, then the user may not even need to run VACUUM, which could be costly
> for very large tables.

FreeSpaceMapTruncateRel()?

> Also, AFAICS we will need to backport
> pg_truncate_visibility_map() to older releases because unless the VM is
> truncated along with the FSM, VACUUM may not scan all pages and the FSM for
> those pages won't be recorded.

This would need a careful lookup, and it would not be that complicated
to implement. And this bug justifies the presence of a tool like that
actually... But usually those don't get a backpatch, so the
probability of getting that backported is low IMO, personally I am not
sure I like that either.
-- 
Michael