Refactor aggregates

sqlalchemy_utils/aggregates.py

@@ -404,7 +404,7 @@ class AggregatedAttribute(declared_attr):
         return desc.column
 
 
-def get_aggregate_query(agg_expr, relationships):
+def aggregate_select(agg_expr, relationships):
     """
     Return a subquery for fetching an aggregate value of given aggregate
     expression and given sequence of relationships.
@@ -474,24 +474,25 @@ def local_condition(prop, objects):
         return column.in_(values)
 
 
+def aggregate_expression(expr, class_):
+    if isinstance(expr, sa.sql.visitors.Visitable):
+        return expr
+    elif isinstance(expr, _FunctionGenerator):
+        return expr(sa.sql.text('1'))
+    else:
+        return expr(class_)
+
+
 class AggregatedValue(object):
     def __init__(self, class_, attr, relationships, expr):
         self.class_ = class_
         self.attr = attr
         self.relationships = relationships
-        self.expr = self.aggregate_expression(expr, class_)
-
-    def aggregate_expression(self, expr, class_):
-        if isinstance(expr, sa.sql.visitors.Visitable):
-            return expr
-        elif isinstance(expr, _FunctionGenerator):
-            return expr(sa.sql.text('1'))
-        else:
-            return expr(class_)
+        self.expr = aggregate_expression(expr, class_)
 
     @property
     def aggregate_query(self):
-        query = get_aggregate_query(self.expr, self.relationships)
+        query = aggregate_select(self.expr, self.relationships)
 
         return query.correlate(self.class_).as_scalar()