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

At Tue, 8 Dec 2020 08:08:25 +0530, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote in
> On Tue, Dec 8, 2020 at 7:24 AM Kyotaro Horiguchi
> <horikyota(dot)ntt(at)gmail(dot)com> wrote:
> > We drop
> > buffers for the old relfilenode on truncation anyway.
> >
> > What I did is:
> >
> > a: Create a physical replication pair.
> > b: On the master, create a table. (without explicitly starting a tx)
> > c: On the master, insert a tuple into the table.
> > d: On the master truncate the table.
> >
> > On the standby, smgrnblocks is called for the old relfilenode of the
> > table at c, then the same function is called for the same relfilenode
> > at d and the function takes the cached path.
> >
>
> This is on the lines I have tried for recovery. So, it seems we are in
> agreement that we can use the 'cached' flag in
> DropRelFileNodesAllBuffers and it will take the optimized path in many
> such cases, right?

Mmm. There seems to be a misunderstanding.. What I opposed to is
referring only to InRecovery and ignoring the value of "cached".

The remaining issue is we don't get to the optimized path when a
standby makes the first call to smgrnblocks() when truncating a
relation. Still we can get to the optimized path as far as any
update(+insert) or select is performed earlier on the relation so I
think it doesn't matter so match.

But I'm not sure what others think.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center