Re: [Patch] Optimize dropping of relation buffers using dlist

On Tue, Dec 8, 2020 at 12:13 PM tsunakawa.takay@fujitsu.com
<tsunakawa.takay@fujitsu.com> wrote:
>
> From: Jamison, Kirk/ジャミソン カーク <k.jamison@fujitsu.com>
> > Because one of the rel's cached value was false, it forced the
> > full-scan path for TRUNCATE.
> > Is there a possible workaround for this?
>
> Hmm, the other two relfilenodes are for the TOAST table and index of the target table.  I think the INSERT didn't
accessthose TOAST relfilenodes because the inserted data was stored in the main storage.  But TRUNCATE always truncates
allthe three relfilenodes.  So, the standby had not opened the relfilenode for the TOAST stuff or cached its size when
replayingthe TRUNCATE. 
>
> I'm afraid this is more common than we can ignore and accept the slow traditional path, but I don't think of a good
ideato use the cached flag. 
>

I also can't think of a way to use an optimized path for such cases
but I don't agree with your comment on if it is common enough that we
leave this optimization entirely for the truncate path.

--
With Regards,
Amit Kapila.