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

I looked at v14.

(1)
+ /* Get the total number of blocks for the supplied relation's fork */
+ for (j = 0; j < nforks; j++)
+ {
+ BlockNumber block = smgrnblocks(smgr_reln, forkNum[j]);
+ nblocks += block;
+ }

Why do you sum all forks?

(2)
+ if ((nblocks / (uint32)NBuffers) < BUF_DROP_FULLSCAN_THRESHOLD &&
+ BlockNumberIsValid(nblocks))
+ {

The division by NBuffers is not necessary, because both sides of = are number of blocks.
Why is BlockNumberIsValid(nblocks)) call needed?

(3)
if (reln->smgr_cached_nblocks[forknum] == blocknum)
reln->smgr_cached_nblocks[forknum] = blocknum + 1;
else
+ {
+ /*
+ * DropRelFileNodeBuffers relies on the behavior that cached nblocks
+ * won't be invalidated by file extension while recovering.
+ */
+ Assert(!InRecovery);
reln->smgr_cached_nblocks[forknum] = InvalidBlockNumber;
+ }

I think this change is not directly related to this patch and can be a separate patch, but I want to leave the decision up to a committer.

Regards
Takayuki Tsunakawa