Add more assertions in hope to find floating bug.

Author: Alexander Korotkov

src/backend/access/heap/heapam.c

@@ -2621,6 +2621,9 @@ heap_page_xid_min_max(Page page, bool multi,
 			if (!HeapTupleHeaderXminFrozen(htup) &&
 				TransactionIdIsNormal(htup->t_choice.t_heap.t_xmin))
 			{
+				Assert(htup->t_choice.t_heap.t_xmin >= FirstNormalTransactionId);
+				Assert(htup->t_choice.t_heap.t_xmin <= MaxShortTransactionId);
+
 				if (!found)
 				{
 					*min = *max = htup->t_choice.t_heap.t_xmin;
@@ -2636,6 +2639,9 @@ heap_page_xid_min_max(Page page, bool multi,
 			if (TransactionIdIsNormal(htup->t_choice.t_heap.t_xmax) &&
 				!(htup->t_infomask & HEAP_XMAX_IS_MULTI))
 			{
+				Assert(htup->t_choice.t_heap.t_xmax >= FirstNormalTransactionId);
+				Assert(htup->t_choice.t_heap.t_xmax <= MaxShortTransactionId);
+
 				if (!found)
 				{
 					*min = *max = htup->t_choice.t_heap.t_xmax;
@@ -2653,6 +2659,9 @@ heap_page_xid_min_max(Page page, bool multi,
 			if (TransactionIdIsNormal(htup->t_choice.t_heap.t_xmax) &&
 				(htup->t_infomask & HEAP_XMAX_IS_MULTI))
 			{
+				Assert(htup->t_choice.t_heap.t_xmax >= FirstNormalTransactionId);
+				Assert(htup->t_choice.t_heap.t_xmax <= MaxShortTransactionId);
+
 				if (!found)
 				{
 					*min = *max = htup->t_choice.t_heap.t_xmax;
@@ -2896,11 +2905,15 @@ heap_page_prepare_for_xid(Relation relation, Buffer buffer,
 
 			delta = (int64) (xid - FirstNormalTransactionId) - (int64) base;
 
+			Assert(xid >= base + delta + FirstNormalTransactionId);
+			Assert(xid <= base + delta + MaxShortTransactionId);
+
 			heap_page_shift_base(relation, buffer, page, multi, delta);
 			MarkBufferDirty(buffer);
 
 			base = multi ? pageSpecial->pd_multi_base : pageSpecial->pd_xid_base;
-			Assert(xid >= base + FirstNormalTransactionId && xid <= base + MaxShortTransactionId);
+			Assert(xid >= base + FirstNormalTransactionId);
+			Assert(xid <= base + MaxShortTransactionId);
 			return false;
 		}
 
@@ -2912,12 +2925,17 @@ heap_page_prepare_for_xid(Relation relation, Buffer buffer,
 
 			if (requiredDelta <= freeDelta)
 			{
-				heap_page_shift_base(relation, buffer,
-					page, multi, - (freeDelta + requiredDelta) / 2);
+				int64	delta = - (freeDelta + requiredDelta) / 2;
+
+				Assert(xid >= base + delta + FirstNormalTransactionId);
+				Assert(xid <= base + delta + MaxShortTransactionId);
+
+				heap_page_shift_base(relation, buffer, page, multi, delta);
 				MarkBufferDirty(buffer);
 
 				base = multi ? pageSpecial->pd_multi_base : pageSpecial->pd_xid_base;
-				Assert(xid >= base + FirstNormalTransactionId && xid <= base + MaxShortTransactionId);
+				Assert(xid >= base + FirstNormalTransactionId);
+				Assert(xid <= base + MaxShortTransactionId);
 				return true;
 			}
 		}
@@ -2926,14 +2944,21 @@ heap_page_prepare_for_xid(Relation relation, Buffer buffer,
 			int64	freeDelta = min - FirstNormalTransactionId,
 					requiredDelta = xid - (base + MaxShortTransactionId);
 
+			Assert(xid > base + MaxShortTransactionId);
+
 			if (requiredDelta <= freeDelta)
 			{
-				heap_page_shift_base(relation, buffer,
-					page, multi, (freeDelta + requiredDelta) / 2);
+				int64	delta = (freeDelta + requiredDelta) / 2;
+
+				Assert(xid >= base + delta + FirstNormalTransactionId);
+				Assert(xid <= base + delta + MaxShortTransactionId);
+
+				heap_page_shift_base(relation, buffer, page, multi, delta);
 				MarkBufferDirty(buffer);
 
 				base = multi ? pageSpecial->pd_multi_base : pageSpecial->pd_xid_base;
-				Assert(xid >= base + FirstNormalTransactionId && xid <= base + MaxShortTransactionId);
+				Assert(xid >= base + FirstNormalTransactionId);
+				Assert(xid <= base + MaxShortTransactionId);
 				return true;
 			}
 		}