| From: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
|---|---|
| To: | Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: FSM corruption leading to errors |
| Date: | 2016-10-20 06:04:02 |
| Message-ID: | CAB7nPqSk+-4dUBEapJz4bN7EXJ12vxOt980+--AO=kQ7+C3=1g@mail.gmail.com |
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On Thu, Oct 20, 2016 at 2:50 PM, Pavan Deolasee
<pavan(dot)deolasee(at)gmail(dot)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
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