diff --git a/src/backend/catalog/catalog.c b/src/backend/catalog/catalog.c
index e3002eb9637c8ff4a368852988e45eee03f11218..282e0b9ae8cba5a023f23157aeb9a0ccdeac9afd 100644
--- a/src/backend/catalog/catalog.c
+++ b/src/backend/catalog/catalog.c
@@ -408,8 +408,8 @@ GetNewOidWithIndex(Relation relation, Oid indexId, AttrNumber oidcolumn)
 
 /*
  * GetNewRelFileNode
- *		Generate a new relfilenode number that is unique within the given
- *		tablespace.
+ *		Generate a new relfilenode number that is unique within the
+ *		database of the given tablespace.
  *
  * If the relfilenode will also be used as the relation's OID, pass the
  * opened pg_class catalog, and this routine will guarantee that the result
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 1de3170249390b977db712fe79bf307d160ea8b8..25f01e5165f2d8b6216cca0fdc9e22398f95a9ab 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -9078,8 +9078,8 @@ ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode)
 	FlushRelationBuffers(rel);
 
 	/*
-	 * Relfilenodes are not unique across tablespaces, so we need to allocate
-	 * a new one in the new tablespace.
+	 * Relfilenodes are not unique in databases across tablespaces, so we
+	 * need to allocate a new one in the new tablespace.
 	 */
 	newrelfilenode = GetNewRelFileNode(newTableSpace, NULL,
 									   rel->rd_rel->relpersistence);
diff --git a/src/include/storage/relfilenode.h b/src/include/storage/relfilenode.h
index c995c10c4d389d16347962a9cd6f2d2715a92177..8616bd3a1ecd9f6b39d272327418c90d9a1abd89 100644
--- a/src/include/storage/relfilenode.h
+++ b/src/include/storage/relfilenode.h
@@ -55,7 +55,8 @@ typedef enum ForkNumber
  * relNode identifies the specific relation.  relNode corresponds to
  * pg_class.relfilenode (NOT pg_class.oid, because we need to be able
  * to assign new physical files to relations in some situations).
- * Notice that relNode is only unique within a particular tablespace.
+ * Notice that relNode is only unique within a database in a particular
+ * tablespace.
  *
  * Note: spcNode must be GLOBALTABLESPACE_OID if and only if dbNode is
  * zero.  We support shared relations only in the "global" tablespace.