Cosmetic cleanup for commit a760893dbd.

Mostly, fixing overlooked comments.

src/backend/access/nbtree/nbtpage.c

@@ -715,7 +715,7 @@ _bt_page_recyclable(Page page)
 }
 
 /*
- * Delete item(s) from a btree page.
+ * Delete item(s) from a btree page during VACUUM.
  *
  * This must only be used for deleting leaf items.	Deleting an item on a
  * non-leaf page has to be done as part of an atomic action that includes
@@ -736,7 +736,8 @@ _bt_page_recyclable(Page page)
  */
 void
 _bt_delitems_vacuum(Relation rel, Buffer buf,
-			OffsetNumber *itemnos, int nitems, BlockNumber lastBlockVacuumed)
+					OffsetNumber *itemnos, int nitems,
+					BlockNumber lastBlockVacuumed)
 {
 	Page		page = BufferGetPage(buf);
 	BTPageOpaque opaque;
@@ -771,7 +772,6 @@ _bt_delitems_vacuum(Relation rel, Buffer buf,
 	{
 		XLogRecPtr	recptr;
 		XLogRecData rdata[2];
-
 		xl_btree_vacuum xlrec_vacuum;
 
 		xlrec_vacuum.node = rel->rd_node;
@@ -811,13 +811,27 @@ _bt_delitems_vacuum(Relation rel, Buffer buf,
 	END_CRIT_SECTION();
 }
 
+/*
+ * Delete item(s) from a btree page during single-page cleanup.
+ *
+ * As above, must only be used on leaf pages.
+ *
+ * This routine assumes that the caller has pinned and locked the buffer.
+ * Also, the given itemnos *must* appear in increasing order in the array.
+ *
+ * This is nearly the same as _bt_delitems_vacuum as far as what it does to
+ * the page, but the WAL logging considerations are quite different.  See
+ * comments for _bt_delitems_vacuum.
+ */
 void
 _bt_delitems_delete(Relation rel, Buffer buf,
-					OffsetNumber *itemnos, int nitems, Relation heapRel)
+					OffsetNumber *itemnos, int nitems,
+					Relation heapRel)
 {
 	Page		page = BufferGetPage(buf);
 	BTPageOpaque opaque;
 
+	/* Shouldn't be called unless there's something to do */
 	Assert(nitems > 0);
 
 	/* No ereport(ERROR) until changes are logged */
@@ -849,7 +863,6 @@ _bt_delitems_delete(Relation rel, Buffer buf,
 	{
 		XLogRecPtr	recptr;
 		XLogRecData rdata[3];
-
 		xl_btree_delete xlrec_delete;
 
 		xlrec_delete.node = rel->rd_node;
@@ -863,8 +876,9 @@ _bt_delitems_delete(Relation rel, Buffer buf,
 		rdata[0].next = &(rdata[1]);
 
 		/*
-		 * We need the target-offsets array whether or not we store the to
-		 * allow us to find the latestRemovedXid on a standby server.
+		 * We need the target-offsets array whether or not we store the whole
+		 * buffer, to allow us to find the latestRemovedXid on a standby
+		 * server.
 		 */
 		rdata[1].data = (char *) itemnos;
 		rdata[1].len = nitems * sizeof(OffsetNumber);

src/backend/access/nbtree/nbtree.c

@@ -1004,14 +1004,15 @@ restart:
 		}
 
 		/*
-		 * Apply any needed deletes.  We issue just one _bt_delitems() call
-		 * per page, so as to minimize WAL traffic.
+		 * Apply any needed deletes.  We issue just one _bt_delitems_vacuum()
+		 * call per page, so as to minimize WAL traffic.
 		 */
 		if (ndeletable > 0)
 		{
 			BlockNumber lastBlockVacuumed = BufferGetBlockNumber(buf);
 
-			_bt_delitems_vacuum(rel, buf, deletable, ndeletable, vstate->lastBlockVacuumed);
+			_bt_delitems_vacuum(rel, buf, deletable, ndeletable,
+								vstate->lastBlockVacuumed);
 
 			/*
 			 * Keep track of the block number of the lastBlockVacuumed, so we
@@ -1031,8 +1032,8 @@ restart:
 			/*
 			 * If the page has been split during this vacuum cycle, it seems
 			 * worth expending a write to clear btpo_cycleid even if we don't
-			 * have any deletions to do.  (If we do, _bt_delitems takes care
-			 * of this.)  This ensures we won't process the page again.
+			 * have any deletions to do.  (If we do, _bt_delitems_vacuum takes
+			 * care of this.)  This ensures we won't process the page again.
 			 *
 			 * We treat this like a hint-bit update because there's no need to
 			 * WAL-log it.

src/backend/access/nbtree/nbtxlog.c

@@ -539,7 +539,7 @@ btree_xlog_vacuum(XLogRecPtr lsn, XLogRecord *record)
 
 	/*
 	 * Mark the page as not containing any LP_DEAD items --- see comments in
-	 * _bt_delitems().
+	 * _bt_delitems_vacuum().
 	 */
 	opaque = (BTPageOpaque) PageGetSpecialPointer(page);
 	opaque->btpo_flags &= ~BTP_HAS_GARBAGE;
@@ -720,7 +720,7 @@ btree_xlog_delete(XLogRecPtr lsn, XLogRecord *record)
 
 	/*
 	 * Mark the page as not containing any LP_DEAD items --- see comments in
-	 * _bt_delitems().
+	 * _bt_delitems_delete().
 	 */
 	opaque = (BTPageOpaque) PageGetSpecialPointer(page);
 	opaque->btpo_flags &= ~BTP_HAS_GARBAGE;

src/include/access/nbtree.h

@@ -635,7 +635,8 @@ extern bool _bt_page_recyclable(Page page);
 extern void _bt_delitems_delete(Relation rel, Buffer buf,
 					OffsetNumber *itemnos, int nitems, Relation heapRel);
 extern void _bt_delitems_vacuum(Relation rel, Buffer buf,
-		   OffsetNumber *itemnos, int nitems, BlockNumber lastBlockVacuumed);
+					OffsetNumber *itemnos, int nitems,
+					BlockNumber lastBlockVacuumed);
 extern int	_bt_pagedel(Relation rel, Buffer buf, BTStack stack);
 
 /*