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

RelationTruncate() invalidates the cached fork sizes as follows.  This causes smgrnblocks() return accurate=false,
resultingin not running optimization.  Try commenting out for non-recovery case. 

    /*
     * Make sure smgr_targblock etc aren't pointing somewhere past new end
     */
    rel->rd_smgr->smgr_targblock = InvalidBlockNumber;
    for (int i = 0; i <= MAX_FORKNUM; ++i)
        rel->rd_smgr->smgr_cached_nblocks[i] = InvalidBlockNumber;


Regards
Takayuki Tsunakawa