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

On Monday, September 28, 2020 5:08 PM, Tsunakawa-san wrote:

> From: Jamison, Kirk/ジャミソン カーク <k(dot)jamison(at)fujitsu(dot)com>
> > Is my understanding above correct?
>
> No. I simply meant DropRelFileNodeBuffers() calls the following function,
> and avoids the optimization if it returns InvalidBlockNumber.
>
>
> BlockNumber
> smgrcachednblocks(SMgrRelation reln, ForkNumber forknum) {
> return reln->smgr_cached_nblocks[forknum];
> }

Thank you for clarifying.

So in the new function, it goes something like:
if (InRecovery)
{
if (reln->smgr_cached_nblocks[forknum] != InvalidBlockNumber)
return reln->smgr_cached_nblocks[forknum];
else
return InvalidBlockNumber;
}

I've revised the patch and added the new function accordingly in the attached file.
I also did not remove the duplicate code from smgrnblocks because Amit-san mentioned
that when the caching for non-recovery cases is implemented, we can use it
for non-recovery cases as well.

Although I am not sure if the way it's written in DropRelFileNodeBuffers is okay.
BlockNumberIsValid(nTotalBlocks)

nTotalBlocks = smgrcachednblocks(smgr_reln, forkNum[j]);
nBlocksToInvalidate = nTotalBlocks - firstDelBlock[j];

if (BlockNumberIsValid(nTotalBlocks) &&
nBlocksToInvalidate < BUF_DROP_FULLSCAN_THRESHOLD)
{
//enter optimization loop
}
else
{
//full scan for each fork
}

Regards,
Kirk Jamison