bitbake/data_smart: Optimise the data store iterator

Since we're going to creat the seen set() anyway, we might as well use
it directly. If we don't do this, we see thousands of function calls
with associated overhead on profiles.

(Bitbake rev: 9d43e3279895639ee4899df635f2546c7ee13737)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/data_smart.py

@@ -401,18 +401,20 @@ class DataSmart(MutableMapping):
                 yield key
 
     def __iter__(self):
-        seen = set()
-        def _keys(d):
-            if "_data" in d:
-                for key in _keys(d["_data"]):
-                    yield key
-
+        def keylist(d):        
+            klist = set()
             for key in d:
-                if key != "_data":
-                    if not key in seen:
-                        seen.add(key)
-                        yield key
-        return _keys(self.dict)
+                if key == "_data":
+                    continue
+                klist.add(key)
+
+            if "_data" in d:
+                klist |= keylist(d["_data"])
+
+            return klist
+
+        for k in keylist(self.dict):
+             yield k
 
     def __len__(self):
         return len(frozenset(self))