Remove obsolete comments and code from prior to f8f4227976.

XLogReadBufferForRedo() and XLogReadBufferForRedoExtended() only return
BLK_NEEDS_REDO if the record LSN is greater than the page LSN, so
the redo routine doesn't need to do the LSN check again.

Discussion: https://postgr.es/m/0c37b80e62b1f3007d5a6d1292bd8fa0c275627a.camel@j-davis.com

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 12be87efed4fef5938afd05bb20f39f0e25c2006..560f1c81a2c0a58e1e5ac6e4e9534fbef102eb38 100644 (file)
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -8827,12 +8827,6 @@ heap_xlog_visible(XLogReaderState *record)
                 * full-page writes.  This exposes us to torn page hazards, but since
                 * we're not inspecting the existing page contents in any way, we
                 * don't care.
-                *
-                * However, all operations that clear the visibility map bit *do* bump
-                * the LSN, and those operations will only be replayed if the XLOG LSN
-                * follows the page LSN.  Thus, if the page LSN has advanced past our
-                * XLOG record's LSN, we mustn't mark the page all-visible, because
-                * the subsequent update won't be replayed to clear the flag.
                 */
                page = BufferGetPage(buffer);
 
@@ -8901,20 +8895,8 @@ heap_xlog_visible(XLogReaderState *record)
                reln = CreateFakeRelcacheEntry(rlocator);
                visibilitymap_pin(reln, blkno, &vmbuffer);
 
-               /*
-                * Don't set the bit if replay has already passed this point.
-                *
-                * It might be safe to do this unconditionally; if replay has passed
-                * this point, we'll replay at least as far this time as we did
-                * before, and if this bit needs to be cleared, the record responsible
-                * for doing so should be again replayed, and clear it.  For right
-                * now, out of an abundance of conservatism, we use the same test here
-                * we did for the heap page.  If this results in a dropped bit, no
-                * real harm is done; and the next VACUUM will fix it.
-                */
-               if (lsn > PageGetLSN(vmpage))
-                       visibilitymap_set(reln, blkno, InvalidBuffer, lsn, vmbuffer,
-                                                         xlrec->cutoff_xid, xlrec->flags);
+               visibilitymap_set(reln, blkno, InvalidBuffer, lsn, vmbuffer,
+                                                 xlrec->cutoff_xid, xlrec->flags);
 
                ReleaseBuffer(vmbuffer);
                FreeFakeRelcacheEntry(reln);