refactor(analysis): always merge frames during windowization

ibis/backends/tests/test_window.py

@@ -1250,6 +1250,15 @@ def test_range_expression_bounds(backend):
     assert len(result) == con.execute(t.count())
 
 
+@pytest.mark.notimpl(["polars", "dask"], raises=com.OperationNotDefinedError)
+@pytest.mark.notyet(
+    ["clickhouse"],
+    reason="clickhouse doesn't implement percent_rank",
+    raises=com.OperationNotDefinedError,
+)
+@pytest.mark.broken(
+    ["pandas"], reason="missing column during execution", raises=KeyError
+)
 def test_rank_followed_by_over_call_merge_frames(backend, alltypes, df):
     # GH #7631
     t = alltypes

ibis/expr/analysis.py

@@ -170,17 +170,28 @@ def wrap_analytic(_, default_frame):
 
 @replace(p.WindowFunction)
 def merge_windows(_, default_frame):
+    if _.frame.start and default_frame.start and _.frame.start != default_frame.start:
+        raise ValueError("Unable to merge windows with conflicting start")
+    if _.frame.end and default_frame.end and _.frame.end != default_frame.end:
+        raise ValueError("Unable to merge windows with conflicting end")
+
+    start = _.frame.start or default_frame.start
+    end = _.frame.end or default_frame.end
     group_by = tuple(toolz.unique(_.frame.group_by + default_frame.group_by))
-    order_by = tuple(toolz.unique(_.frame.order_by + default_frame.order_by))
-    frame = _.frame.copy(group_by=group_by, order_by=order_by)
+
+    order_by = {}
+    for sort_key in _.frame.order_by + default_frame.order_by:
+        order_by[sort_key.expr] = sort_key.ascending
+    order_by = tuple(ops.SortKey(k, v) for k, v in order_by.items())
+
+    frame = _.frame.copy(start=start, end=end, group_by=group_by, order_by=order_by)
     return ops.WindowFunction(_.func, frame)
 
 
-def windowize_function(expr, default_frame, merge_frames=False):
+def windowize_function(expr, default_frame):
     ctx = {"default_frame": default_frame}
     node = expr.op()
-    if merge_frames:
-        node = node.replace(merge_windows, filter=p.Value, context=ctx)
+    node = node.replace(merge_windows, filter=p.Value, context=ctx)
     node = node.replace(wrap_analytic, filter=p.Value & ~p.WindowFunction, context=ctx)
     return node.to_expr()
 

ibis/expr/types/core.py

@@ -589,7 +589,8 @@ def to_torch(
 
     def unbind(self) -> ir.Table:
         """Return an expression built on `UnboundTable` instead of backend-specific objects."""
-        from ibis.expr.analysis import p, c, _
+        from ibis.expr.analysis import p, c
+        from ibis.common.deferred import _
 
         rule = p.DatabaseTable >> c.UnboundTable(name=_.name, schema=_.schema)
         return self.op().replace(rule).to_expr()

ibis/expr/types/generic.py

@@ -758,7 +758,7 @@ def over(
 
         def bind(table):
             frame = window.bind(table)
-            expr = an.windowize_function(self, frame, merge_frames=True)
+            expr = an.windowize_function(self, frame)
             if expr.equals(self):
                 raise com.IbisTypeError(
                     "No reduction or analytic function found to construct a window expression"

ibis/expr/types/groupby.py

@@ -254,12 +254,12 @@ def _selectables(self, *exprs, **kwexprs):
             order_by=bind_expr(self.table, self._order_by),
         )
         return [
-            an.windowize_function(e2, default_frame, merge_frames=True)
+            an.windowize_function(e2, default_frame)
             for expr in exprs
             for e1 in util.promote_list(expr)
             for e2 in util.promote_list(table._ensure_expr(e1))
         ] + [
-            an.windowize_function(e, default_frame, merge_frames=True).name(k)
+            an.windowize_function(e, default_frame).name(k)
             for k, expr in kwexprs.items()
             for e in util.promote_list(table._ensure_expr(expr))
         ]

ibis/expr/types/relations.py

@@ -4338,7 +4338,8 @@ def _resolve_predicates(
     table: Table, predicates
 ) -> tuple[list[ir.BooleanValue], list[tuple[ir.BooleanValue, ir.Table]]]:
     import ibis.expr.types as ir
-    from ibis.expr.analysis import _, flatten_predicate, p
+    from ibis.common.deferred import _
+    from ibis.expr.analysis import flatten_predicate, p
 
     # TODO(kszucs): clean this up, too much flattening and resolving happens here
     predicates = [

ibis/tests/expr/test_window_functions.py

@@ -1,5 +1,7 @@
 from __future__ import annotations
 
+import pytest
+
 import ibis
 import ibis.expr.operations as ops
 
@@ -48,15 +50,22 @@ def test_value_over_api(alltypes):
     w1 = ibis.window(rows=(0, 1), group_by=t.g, order_by=[t.f, t.h])
     w2 = ibis.window(range=(-1, 1), group_by=[t.g, t.a], order_by=[t.f])
 
-    expr = t.f.cumsum().over(rows=(0, 1), group_by=t.g, order_by=[t.f, t.h])
-    expected = t.f.cumsum().over(w1)
+    expr = t.f.sum().over(rows=(0, 1), group_by=t.g, order_by=[t.f, t.h])
+    expected = t.f.sum().over(w1)
     assert expr.equals(expected)
 
-    expr = t.f.cumsum().over(range=(-1, 1), group_by=[t.g, t.a], order_by=[t.f])
-    expected = t.f.cumsum().over(w2)
+    expr = t.f.sum().over(range=(-1, 1), group_by=[t.g, t.a], order_by=[t.f])
+    expected = t.f.sum().over(w2)
     assert expr.equals(expected)
 
 
+def test_conflicting_window_boundaries(alltypes):
+    t = alltypes
+
+    with pytest.raises(ValueError):
+        t.f.cumsum().over(rows=(0, 1))
+
+
 def test_rank_followed_by_over_call_merge_frames(alltypes):
     t = alltypes
     expr1 = t.f.percent_rank().over(ibis.window(group_by=t.f.notnull()))