diff --git a/src/backend/partitioning/partdesc.c b/src/backend/partitioning/partdesc.c
index b207b765f2..7f15774266 100644
--- a/src/backend/partitioning/partdesc.c
+++ b/src/backend/partitioning/partdesc.c
@@ -72,6 +72,15 @@ RelationBuildPartitionDesc(Relation rel)
 	MemoryContext oldcxt;
 	int		   *mapping;
 
+	MemoryContext	tmp;
+	MemoryContext	old;
+
+	tmp = AllocSetContextCreate(CurrentMemoryContext,
+								"tmp context",
+								ALLOCSET_SMALL_SIZES);
+
+	old = MemoryContextSwitchTo(tmp);
+
 	/*
 	 * Get partition oids from pg_inherits.  This uses a single snapshot to
 	 * fetch the list of children, so while more children may be getting added
@@ -231,6 +240,9 @@ RelationBuildPartitionDesc(Relation rel)
 		}
 	}
 
+	MemoryContextSwitchTo(old);
+	MemoryContextDelete(tmp);
+
 	rel->rd_partdesc = partdesc;
 }