Update obsolete index scan TID comments.

Oversight in commit c2fe139.

Author: petergeoghegan

src/backend/access/hash/hashsearch.c

@@ -37,8 +37,8 @@ static void _hash_readnext(IndexScanDesc scan, Buffer *bufp,
  *		be pinned but not locked, and so->currPos.itemIndex identifies
  *		which item was previously returned.
  *
- *		On successful exit, scan->xs_ctup.t_self is set to the TID
- *		of the next heap tuple. so->currPos is updated as needed.
+ *		On successful exit, scan->xs_heaptid is set to the TID of the next
+ *		heap tuple.  so->currPos is updated as needed.
  *
  *		On failure exit (no more tuples), we return false with pin
  *		held on bucket page but no pins or locks held on overflow
@@ -279,7 +279,7 @@ _hash_readprev(IndexScanDesc scan,
  *		overflow page, both pin and lock are released whereas if it is a bucket
  *		page then it is pinned but not locked and data about the matching
  *		tuple(s) on the page has been loaded into so->currPos,
- *		scan->xs_ctup.t_self is set to the heap TID of the current tuple.
+ *		scan->xs_heaptid is set to the heap TID of the current tuple.
  *
  *		On failure exit (no more tuples), we return false, with pin held on
  *		bucket page but no pins or locks held on overflow page.

src/backend/access/nbtree/nbtsearch.c

@@ -861,8 +861,8 @@ _bt_compare(Relation rel,
  *		qualifications in the scan key.  On success exit, the page containing
  *		the current index tuple is pinned but not locked, and data about
  *		the matching tuple(s) on the page has been loaded into so->currPos.
- *		scan->xs_ctup.t_self is set to the heap TID of the current tuple,
- *		and if requested, scan->xs_itup points to a copy of the index tuple.
+ *		scan->xs_heaptid is set to the heap TID of the current tuple, and if
+ *		requested, scan->xs_itup points to a copy of the index tuple.
  *
  * If there are no matching items in the index, we return false, with no
  * pins or locks held.
@@ -1448,9 +1448,9 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
  *		but is not locked, and so->currPos.itemIndex identifies which item was
  *		previously returned.
  *
- *		On successful exit, scan->xs_ctup.t_self is set to the TID of the
- *		next heap tuple, and if requested, scan->xs_itup points to a copy of
- *		the index tuple.  so->currPos is updated as needed.
+ *		On successful exit, scan->xs_heaptid is set to the TID of the next
+ *		heap tuple, and if requested, scan->xs_itup points to a copy of the
+ *		index tuple.  so->currPos is updated as needed.
  *
  *		On failure exit (no more tuples), we release pin and set
  *		so->currPos.buf to InvalidBuffer.