diff --git a/src/backend/backup/basebackup_incremental.c b/src/backend/backup/basebackup_incremental.c
index 275615877e..e2a73d8840 100644
--- a/src/backend/backup/basebackup_incremental.c
+++ b/src/backend/backup/basebackup_incremental.c
@@ -740,7 +740,7 @@ GetFileBackupMethod(IncrementalBackupInfo *ib, const char *path,
 	 */
 	rlocator.spcOid = spcoid;
 	rlocator.dbOid = dboid;
-	rlocator.relNumber = 0;
+	rlocator.relNumber = InvalidRelFileNumber;
 	if (BlockRefTableGetEntry(ib->brtab, &rlocator, MAIN_FORKNUM,
 							  &limit_block) != NULL)
 	{
diff --git a/src/backend/bootstrap/bootparse.y b/src/backend/bootstrap/bootparse.y
index 73a7592fb7..2f7f06a126 100644
--- a/src/backend/bootstrap/bootparse.y
+++ b/src/backend/bootstrap/bootparse.y
@@ -206,7 +206,7 @@ Boot_CreateStmt:
 												   PG_CATALOG_NAMESPACE,
 												   shared_relation ? GLOBALTABLESPACE_OID : 0,
 												   $3,
-												   InvalidOid,
+												   InvalidRelFileNumber,
 												   HEAP_TABLE_AM_OID,
 												   tupdesc,
 												   RELKIND_RELATION,
diff --git a/src/backend/catalog/Catalog.pm b/src/backend/catalog/Catalog.pm
index 8e709524cb..74d74ec1f8 100644
--- a/src/backend/catalog/Catalog.pm
+++ b/src/backend/catalog/Catalog.pm
@@ -32,6 +32,7 @@ sub ParseHeader
 		'int32' => 'int4',
 		'int64' => 'int8',
 		'Oid' => 'oid',
+		'RelFileNumber' => 'oid',
 		'NameData' => 'name',
 		'TransactionId' => 'xid',
 		'XLogRecPtr' => 'pg_lsn');
diff --git a/src/backend/catalog/heap.c b/src/backend/catalog/heap.c
index c54a543c53..340faeeab7 100644
--- a/src/backend/catalog/heap.c
+++ b/src/backend/catalog/heap.c
@@ -346,7 +346,7 @@ heap_create(const char *relname,
 		 * with oid same as relid.
 		 */
 		if (!RelFileNumberIsValid(relfilenumber))
-			relfilenumber = relid;
+			relfilenumber = (RelFileNumber) relid;
 	}
 
 	/*
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index f9bb721c5f..53e489be44 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -3740,7 +3740,8 @@ reindex_index(const ReindexStmt *stmt, Oid indexId,
 	if (set_tablespace)
 	{
 		/* Update its pg_class row */
-		SetRelationTableSpace(iRel, params->tablespaceOid, InvalidOid);
+		SetRelationTableSpace(iRel, params->tablespaceOid,
+							  InvalidRelFileNumber);
 
 		/*
 		 * Schedule unlinking of the old index storage at transaction commit.
diff --git a/src/backend/catalog/storage.c b/src/backend/catalog/storage.c
index f56b3cc0f2..316d393b84 100644
--- a/src/backend/catalog/storage.c
+++ b/src/backend/catalog/storage.c
@@ -612,7 +612,8 @@ RestorePendingSyncs(char *startAddress)
 	RelFileLocator *rlocator;
 
 	Assert(pendingSyncHash == NULL);
-	for (rlocator = (RelFileLocator *) startAddress; rlocator->relNumber != 0;
+	for (rlocator = (RelFileLocator *) startAddress;
+		 rlocator->relNumber != InvalidRelFileNumber;
 		 rlocator++)
 		AddPendingSync(rlocator);
 }
diff --git a/src/backend/catalog/toasting.c b/src/backend/catalog/toasting.c
index ad3082c62a..b6b16bc9fe 100644
--- a/src/backend/catalog/toasting.c
+++ b/src/backend/catalog/toasting.c
@@ -319,7 +319,7 @@ create_toast_table(Relation rel, Oid toastOid, Oid toastIndexOid,
 	coloptions[1] = 0;
 
 	index_create(toast_rel, toast_idxname, toastIndexOid, InvalidOid,
-				 InvalidOid, InvalidOid,
+				 InvalidOid, InvalidRelFileNumber,
 				 indexInfo,
 				 list_make2("chunk_id", "chunk_seq"),
 				 BTREE_AM_OID,
diff --git a/src/backend/commands/cluster.c b/src/backend/commands/cluster.c
index ae0863d9a2..0ae521163b 100644
--- a/src/backend/commands/cluster.c
+++ b/src/backend/commands/cluster.c
@@ -1072,6 +1072,7 @@ swap_relation_files(Oid r1, Oid r2, bool target_is_pg_class,
 	RelFileNumber relfilenumber1,
 				relfilenumber2;
 	RelFileNumber swaptemp;
+	Oid 		swaptempoid;
 	char		swptmpchr;
 	Oid			relam1,
 				relam2;
@@ -1107,13 +1108,13 @@ swap_relation_files(Oid r1, Oid r2, bool target_is_pg_class,
 		relform1->relfilenode = relform2->relfilenode;
 		relform2->relfilenode = swaptemp;
 
-		swaptemp = relform1->reltablespace;
+		swaptempoid = relform1->reltablespace;
 		relform1->reltablespace = relform2->reltablespace;
-		relform2->reltablespace = swaptemp;
+		relform2->reltablespace = swaptempoid;
 
-		swaptemp = relform1->relam;
+		swaptempoid = relform1->relam;
 		relform1->relam = relform2->relam;
-		relform2->relam = swaptemp;
+		relform2->relam = swaptempoid;
 
 		swptmpchr = relform1->relpersistence;
 		relform1->relpersistence = relform2->relpersistence;
@@ -1122,9 +1123,9 @@ swap_relation_files(Oid r1, Oid r2, bool target_is_pg_class,
 		/* Also swap toast links, if we're swapping by links */
 		if (!swap_toast_by_content)
 		{
-			swaptemp = relform1->reltoastrelid;
+			swaptempoid = relform1->reltoastrelid;
 			relform1->reltoastrelid = relform2->reltoastrelid;
-			relform2->reltoastrelid = swaptemp;
+			relform2->reltoastrelid = swaptempoid;
 		}
 	}
 	else
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index eaa8142427..8505cc8c1b 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -15441,7 +15441,7 @@ ATExecSetTableSpaceNoStorage(Relation rel, Oid newTableSpace)
 	}
 
 	/* Update can be done, so change reltablespace */
-	SetRelationTableSpace(rel, newTableSpace, InvalidOid);
+	SetRelationTableSpace(rel, newTableSpace, InvalidRelFileNumber);
 
 	InvokeObjectPostAlterHook(RelationRelationId, RelationGetRelid(rel), 0);
 
diff --git a/src/backend/postmaster/walsummarizer.c b/src/backend/postmaster/walsummarizer.c
index 48350bec52..4ca9b52b04 100644
--- a/src/backend/postmaster/walsummarizer.c
+++ b/src/backend/postmaster/walsummarizer.c
@@ -1277,7 +1277,7 @@ SummarizeDbaseRecord(XLogReaderState *xlogreader, BlockRefTable *brtab)
 			(xl_dbase_create_file_copy_rec *) XLogRecGetData(xlogreader);
 		rlocator.spcOid = xlrec->tablespace_id;
 		rlocator.dbOid = xlrec->db_id;
-		rlocator.relNumber = 0;
+		rlocator.relNumber = InvalidRelFileNumber;
 		BlockRefTableSetLimitBlock(brtab, &rlocator, MAIN_FORKNUM, 0);
 	}
 	else if (info == XLOG_DBASE_CREATE_WAL_LOG)
@@ -1288,7 +1288,7 @@ SummarizeDbaseRecord(XLogReaderState *xlogreader, BlockRefTable *brtab)
 		xlrec = (xl_dbase_create_wal_log_rec *) XLogRecGetData(xlogreader);
 		rlocator.spcOid = xlrec->tablespace_id;
 		rlocator.dbOid = xlrec->db_id;
-		rlocator.relNumber = 0;
+		rlocator.relNumber = InvalidRelFileNumber;
 		BlockRefTableSetLimitBlock(brtab, &rlocator, MAIN_FORKNUM, 0);
 	}
 	else if (info == XLOG_DBASE_DROP)
@@ -1299,7 +1299,7 @@ SummarizeDbaseRecord(XLogReaderState *xlogreader, BlockRefTable *brtab)
 
 		xlrec = (xl_dbase_drop_rec *) XLogRecGetData(xlogreader);
 		rlocator.dbOid = xlrec->db_id;
-		rlocator.relNumber = 0;
+		rlocator.relNumber = InvalidRelFileNumber;
 		for (i = 0; i < xlrec->ntablespaces; ++i)
 		{
 			rlocator.spcOid = xlrec->tablespace_ids[i];
diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c
index cc8a80ee96..a6721189ad 100644
--- a/src/backend/storage/smgr/md.c
+++ b/src/backend/storage/smgr/md.c
@@ -1453,7 +1453,7 @@ ForgetDatabaseSyncRequests(Oid dbid)
 
 	rlocator.dbOid = dbid;
 	rlocator.spcOid = 0;
-	rlocator.relNumber = 0;
+	rlocator.relNumber = InvalidRelFileNumber;
 
 	INIT_MD_FILETAG(tag, rlocator, InvalidForkNumber, InvalidBlockNumber);
 
diff --git a/src/backend/utils/adt/dbsize.c b/src/backend/utils/adt/dbsize.c
index e63e99c141..ac12459361 100644
--- a/src/backend/utils/adt/dbsize.c
+++ b/src/backend/utils/adt/dbsize.c
@@ -890,7 +890,7 @@ pg_relation_filenode(PG_FUNCTION_ARGS)
 
 	if (RELKIND_HAS_STORAGE(relform->relkind))
 	{
-		if (relform->relfilenode)
+		if (RelFileNumberIsValid(relform->relfilenode))
 			result = relform->relfilenode;
 		else					/* Consult the relation mapper */
 			result = RelationMapOidToFilenumber(relid,
@@ -973,7 +973,7 @@ pg_relation_filepath(PG_FUNCTION_ARGS)
 			rlocator.dbOid = InvalidOid;
 		else
 			rlocator.dbOid = MyDatabaseId;
-		if (relform->relfilenode)
+		if (RelFileNumberIsValid(relform->relfilenode))
 			rlocator.relNumber = relform->relfilenode;
 		else					/* Consult the relation mapper */
 			rlocator.relNumber = RelationMapOidToFilenumber(relid,
diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index 5bbb654a5d..63c8055135 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -3746,23 +3746,23 @@ RelationSetNewRelfilenumber(Relation relation, char persistence)
 	}
 	else if (relation->rd_rel->relkind == RELKIND_INDEX)
 	{
-		if (!OidIsValid(binary_upgrade_next_index_pg_class_relfilenumber))
+		if (!RelFileNumberIsValid(binary_upgrade_next_index_pg_class_relfilenumber))
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("index relfilenumber value not set when in binary upgrade mode")));
 
 		newrelfilenumber = binary_upgrade_next_index_pg_class_relfilenumber;
-		binary_upgrade_next_index_pg_class_relfilenumber = InvalidOid;
+		binary_upgrade_next_index_pg_class_relfilenumber = InvalidRelFileNumber;
 	}
 	else if (relation->rd_rel->relkind == RELKIND_RELATION)
 	{
-		if (!OidIsValid(binary_upgrade_next_heap_pg_class_relfilenumber))
+		if (!RelFileNumberIsValid(binary_upgrade_next_heap_pg_class_relfilenumber))
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("heap relfilenumber value not set when in binary upgrade mode")));
 
 		newrelfilenumber = binary_upgrade_next_heap_pg_class_relfilenumber;
-		binary_upgrade_next_heap_pg_class_relfilenumber = InvalidOid;
+		binary_upgrade_next_heap_pg_class_relfilenumber = InvalidRelFileNumber;
 	}
 	else
 		ereport(ERROR,
diff --git a/src/include/catalog/pg_class.h b/src/include/catalog/pg_class.h
index 0fc2c093b0..48ebbc4b0d 100644
--- a/src/include/catalog/pg_class.h
+++ b/src/include/catalog/pg_class.h
@@ -54,7 +54,7 @@ CATALOG(pg_class,1259,RelationRelationId) BKI_BOOTSTRAP BKI_ROWTYPE_OID(83,Relat
 
 	/* identifier of physical storage file */
 	/* relfilenode == 0 means it is a "mapped" relation, see relmapper.c */
-	Oid			relfilenode BKI_DEFAULT(0);
+	RelFileNumber	relfilenode BKI_DEFAULT(0);
 
 	/* identifier of table space for relation (0 means default for database) */
 	Oid			reltablespace BKI_DEFAULT(0) BKI_LOOKUP_OPT(pg_tablespace);
diff --git a/src/include/common/relpath.h b/src/include/common/relpath.h
index 2dabbe01ec..82f33c5b87 100644
--- a/src/include/common/relpath.h
+++ b/src/include/common/relpath.h
@@ -22,7 +22,6 @@
 /*
  * RelFileNumber data type identifies the specific relation file name.
  */
-typedef Oid RelFileNumber;
 #define InvalidRelFileNumber		((RelFileNumber) InvalidOid)
 #define RelFileNumberIsValid(relnumber) \
 				((bool) ((relnumber) != InvalidRelFileNumber))
diff --git a/src/include/postgres_ext.h b/src/include/postgres_ext.h
index 240ad4e93b..ef6f26fd47 100644
--- a/src/include/postgres_ext.h
+++ b/src/include/postgres_ext.h
@@ -30,6 +30,8 @@
  */
 typedef unsigned int Oid;
 
+typedef Oid RelFileNumber;
+
 #ifdef __cplusplus
 #define InvalidOid		(Oid(0))
 #else