add some annotations to pd_xid_base decoding

Author: kelvich

src/backend/access/rmgrdesc/heapdesc.c

@@ -56,6 +56,7 @@ heap_desc(StringInfo buf, XLogReaderState *record)
 	{
 		xl_heap_update *xlrec;
 
+		/* step over pd_xid_base */
 		if (isinit)
 			rec += sizeof(TransactionId);
 

src/backend/replication/logical/decode.c

@@ -778,8 +778,11 @@ DecodeInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 	Pointer		rec_data;
 
 	rec_data = (Pointer) XLogRecGetData(r);
+
+	/* step over pd_xid_base */
 	if (isinit)
 		rec_data += sizeof(TransactionId);
+
 	xlrec = (xl_heap_insert *) rec_data;
 
 	/* only interested in our database */
@@ -835,8 +838,11 @@ DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 	Pointer		rec_data;
 
 	rec_data = (Pointer) XLogRecGetData(r);
+
+	/* step over pd_xid_base */
 	if (isinit)
 		rec_data += sizeof(TransactionId);
+
 	xlrec = (xl_heap_update *) rec_data;
 
 	/* only interested in our database */
@@ -876,6 +882,8 @@ DecodeUpdate(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 		/* caution, remaining data in record is not aligned */
 		data = XLogRecGetData(r) + SizeOfHeapUpdate;
 		datalen = XLogRecGetDataLen(r) - SizeOfHeapUpdate;
+
+		/* step over pd_xid_base */
 		if (isinit)
 		{
 			data += sizeof(TransactionId);
@@ -970,8 +978,11 @@ DecodeMultiInsert(LogicalDecodingContext *ctx, XLogRecordBuffer *buf)
 	Pointer		rec_data;
 
 	rec_data = (Pointer) XLogRecGetData(r);
+
+	/* step over pd_xid_base */
 	if (isinit)
 		rec_data += sizeof(TransactionId);
+
 	xlrec = (xl_heap_multi_insert *) rec_data;
 
 	/* only interested in our database */