refactor(clickhouse): use a pattern for one-to-zero index conversion …

…of ranking window functions

ibis/backends/clickhouse/compiler/core.py

@@ -113,13 +113,22 @@ def fn(node, _, **kwargs):
     replace_notany_with_min_not = p.NotAny(x, where=y) >> c.Min(c.Not(x), where=y)
     replace_notall_with_max_not = p.NotAll(x, where=y) >> c.Max(c.Not(x), where=y)
 
+    # subtract one from ranking functions to convert from 1-indexed to 0-indexed
+    subtract_one_from_ranking_functions = p.WindowFunction(
+        p.RankBase | p.NTile
+    ) >> c.Subtract(_, 1)
+
+    add_one_to_nth_value_input = p.NthValue >> _.copy(nth=c.Add(_.nth, 1))
+
     op = op.replace(
         replace_literals
         | replace_in_column_with_table_array_view
         | replace_empty_in_values_with_false
         | replace_notexists_subquery_with_not_exists
         | replace_notany_with_min_not
         | replace_notall_with_max_not
+        | subtract_one_from_ranking_functions
+        | add_one_to_nth_value_input
     )
     # apply translate rules in topological order
     results = op.map(fn, filter=(ops.TableNode, ops.Value))

ibis/backends/clickhouse/compiler/values.py

@@ -569,7 +569,7 @@ def _struct_field(op, *, arg, field: str, **_):
 
 @translate_val.register(ops.NthValue)
 def _nth_value(op, *, arg, nth, **_):
-    return F.nth_value(arg, _parenthesize(op.nth, nth) + 1)
+    return F.nth_value(arg, _parenthesize(op.nth, nth))
 
 
 @translate_val.register(ops.Repeat)
@@ -898,12 +898,8 @@ def _window_frame(op, *, group_by, order_by, start, end, max_lookback=None, **_)
 
 @translate_val.register(ops.WindowFunction)
 def _window(op: ops.WindowFunction, *, func, frame, **_: Any):
-    window = frame(this=func)
-
-    # preserve zero-based indexing
-    if isinstance(op.func, ops.RankBase):
-        return window - 1
-    return window
+    # frame is a partial call to sg.exp.Window
+    return frame(this=func)
 
 
 def shift_like(op_class, func):