add comment explaining why we don't set window bounds for shift opera…

…tions in pyspark backend
ibis-project · Oct 23, 2019 · e4ad7f0 · e4ad7f0
1 parent e94945c
commit e4ad7f0
Showing 1 changed file with 2 additions and 0 deletions.
diff --git a/ibis/pyspark/compiler.py b/ibis/pyspark/compiler.py
@@ -991,6 +991,8 @@ def compile_window_op(t, expr, scope, **kwargs):
 
     pyspark_window = Window.partitionBy(grouping_keys).orderBy(ordering_keys)
 
+    # If the operand is a shift op (e.g. lead, lag), Spark will set the window
+    # bounds. Only set window bounds here if not a shift operation.
     if not isinstance(operand.op(), ops.ShiftBase):
         start = (
             -window.preceding