hack deferred value fix

Author: TrevorBergeron

bigframes/core/compile/compiled.py

@@ -474,8 +474,9 @@ def project_window_op(
             else:
                 # Operations like count treat even NULLs as valid observations for the sake of min_periods
                 # notnull is just used to convert null values to non-null (FALSE) values to be counted
+                is_observation = ops.notnull_op.as_expr(expression.inputs[0])
                 observation_count_expr = agg_expressions.WindowExpression(
-                    agg_ops.size_op.as_expr(),
+                    agg_ops.count_op.as_expr(is_observation),
                     window_spec,
                 )
             clauses.append(

third_party/bigframes_vendored/ibis/expr/types/generic.py

@@ -773,7 +773,9 @@ def over(
 
         @deferrable
         def bind(table):
-            winfunc = rewrite_window_input(node, window.bind(table))
+            winfunc = rewrite_window_input(
+                node, window.bind(table) if table else window
+            )
             if winfunc == node:
                 raise com.IbisTypeError(
                     "No reduction or analytic function found to construct a window expression"
@@ -782,7 +784,7 @@ def bind(table):
 
         try:
             return bind(table)
-        except com.IbisInputError:
+        except com.IbisInputError as e:
             return bind(_)
 
     def isnull(self) -> ir.BooleanValue: