chore: allow PRECEDING and FOLLOWING to appear on both side of BETWEEN when windowing

bigframes/core/block_transforms.py

@@ -213,8 +213,8 @@ def _interpolate_column(
     if interpolate_method not in ["linear", "nearest", "ffill"]:
         raise ValueError("interpolate method not supported")
     window_ordering = (ordering.OrderingExpression(ex.deref(x_values)),)
-    backwards_window = windows.rows(following=0, ordering=window_ordering)
-    forwards_window = windows.rows(preceding=0, ordering=window_ordering)
+    backwards_window = windows.rows(end=0, ordering=window_ordering)
+    forwards_window = windows.rows(start=0, ordering=window_ordering)
 
     # Note, this method may
     block, notnull = block.apply_unary_op(column, ops.notnull_op)
@@ -450,7 +450,7 @@ def rank(
             )
             if method == "dense"
             else windows.rows(
-                following=0, ordering=window_ordering, grouping_keys=grouping_cols
+                end=0, ordering=window_ordering, grouping_keys=grouping_cols
             ),
             skip_reproject_unsafe=(col != columns[-1]),
         )

bigframes/core/compile/compiled.py

@@ -21,7 +21,9 @@
 import bigframes_vendored.ibis
 import bigframes_vendored.ibis.backends.bigquery.backend as ibis_bigquery
 import bigframes_vendored.ibis.common.deferred as ibis_deferred  # type: ignore
+from bigframes_vendored.ibis.expr import builders as ibis_expr_builders
 import bigframes_vendored.ibis.expr.datatypes as ibis_dtypes
+from bigframes_vendored.ibis.expr.operations import window as ibis_expr_window
 import bigframes_vendored.ibis.expr.operations as ibis_ops
 import bigframes_vendored.ibis.expr.types as ibis_types
 import pandas
@@ -551,20 +553,9 @@ def _ibis_window_from_spec(self, window_spec: WindowSpec):
             # Unbound grouping window. Suitable for aggregations but not for analytic function application.
             order_by = None
 
-        bounds = window_spec.bounds
         window = bigframes_vendored.ibis.window(order_by=order_by, group_by=group_by)
-        if bounds is not None:
-            if isinstance(bounds, RangeWindowBounds):
-                window = window.preceding_following(
-                    bounds.preceding, bounds.following, how="range"
-                )
-            if isinstance(bounds, RowsWindowBounds):
-                if bounds.preceding is not None or bounds.following is not None:
-                    window = window.preceding_following(
-                        bounds.preceding, bounds.following, how="rows"
-                    )
-            else:
-                raise ValueError(f"unrecognized window bounds {bounds}")
+        if window_spec.bounds is not None:
+            return _add_boundary(window_spec.bounds, window)
         return window
 
 
@@ -681,3 +672,33 @@ def _as_groupable(value: ibis_types.Value):
         return scalar_op_compiler.to_json_string(value)
     else:
         return value
+
+
+def _to_ibis_boundary(
+    boundary: Optional[int],
+) -> Optional[ibis_expr_window.WindowBoundary]:
+    if boundary is None:
+        return None
+    return ibis_expr_window.WindowBoundary(
+        abs(boundary), preceding=boundary <= 0  # type:ignore
+    )
+
+
+def _add_boundary(
+    bounds: typing.Union[RowsWindowBounds, RangeWindowBounds],
+    ibis_window: ibis_expr_builders.LegacyWindowBuilder,
+) -> ibis_expr_builders.LegacyWindowBuilder:
+    if isinstance(bounds, RangeWindowBounds):
+        return ibis_window.range(
+            start=_to_ibis_boundary(bounds.start),
+            end=_to_ibis_boundary(bounds.end),
+        )
+    if isinstance(bounds, RowsWindowBounds):
+        if bounds.start is not None or bounds.end is not None:
+            return ibis_window.rows(
+                start=_to_ibis_boundary(bounds.start),
+                end=_to_ibis_boundary(bounds.end),
+            )
+        return ibis_window
+    else:
+        raise ValueError(f"unrecognized window bounds {bounds}")

bigframes/core/compile/polars/compiler.py

@@ -16,9 +16,10 @@
 import dataclasses
 import functools
 import itertools
-from typing import cast, Sequence, Tuple, TYPE_CHECKING
+from typing import cast, Optional, Sequence, Tuple, TYPE_CHECKING, Union
 
 import bigframes.core
+from bigframes.core import window_spec
 import bigframes.core.expression as ex
 import bigframes.core.guid as guid
 import bigframes.core.nodes as nodes
@@ -366,23 +367,8 @@ def compile_window(self, node: nodes.WindowOpNode):
             indexed_df = df.with_row_index(index_col_name)
             if len(window.grouping_keys) == 0:  # rolling-only window
                 # https://docs.pola.rs/api/python/stable/reference/dataframe/api/polars.DataFrame.rolling.html
-                finite = (
-                    window.bounds.preceding is not None
-                    and window.bounds.following is not None
-                )
-                offset_n = (
-                    None
-                    if window.bounds.preceding is None
-                    else -window.bounds.preceding
-                )
-                # collecting height is a massive kludge
-                period_n = (
-                    df.collect().height
-                    if not finite
-                    else cast(int, window.bounds.preceding)
-                    + cast(int, window.bounds.following)
-                    + 1
-                )
+                offset_n = window.bounds.start
+                period_n = _get_period(window.bounds) or df.collect().height
                 results = indexed_df.rolling(
                     index_column=index_col_name,
                     period=f"{period_n}i",
@@ -395,3 +381,14 @@ def compile_window(self, node: nodes.WindowOpNode):
             # polars is columnar, so this is efficient
             # TODO: why can't just add columns?
             return pl.concat([df, results], how="horizontal")
+
+
+def _get_period(
+    bounds: Union[window_spec.RowsWindowBounds, window_spec.RangeWindowBounds]
+) -> Optional[int]:
+    """Returns None if the boundary is infinite."""
+    if bounds.start is None or bounds.end is None:
+        return None
+
+    # collecting height is a massive kludge
+    return bounds.end - bounds.start + 1

bigframes/core/groupby/__init__.py

@@ -309,8 +309,8 @@ def rolling(self, window: int, min_periods=None) -> windows.Window:
         # To get n size window, need current row and n-1 preceding rows.
         window_spec = window_specs.rows(
             grouping_keys=tuple(self._by_col_ids),
-            preceding=window - 1,
-            following=0,
+            start=-(window - 1),
+            end=0,
             min_periods=min_periods or window,
         )
         block = self._block.order_by(
@@ -742,8 +742,8 @@ def rolling(self, window: int, min_periods=None) -> windows.Window:
         # To get n size window, need current row and n-1 preceding rows.
         window_spec = window_specs.rows(
             grouping_keys=tuple(self._by_col_ids),
-            preceding=window - 1,
-            following=0,
+            start=-(window - 1),
+            end=0,
             min_periods=min_periods or window,
         )
         block = self._block.order_by(

bigframes/core/window_spec.py

@@ -52,8 +52,8 @@ def unbound(
 ### Rows-based Windows
 def rows(
     grouping_keys: Tuple[str, ...] = (),
-    preceding: Optional[int] = None,
-    following: Optional[int] = None,
+    start: Optional[int] = None,
+    end: Optional[int] = None,
     min_periods: int = 0,
     ordering: Tuple[orderings.OrderingExpression, ...] = (),
 ) -> WindowSpec:
@@ -63,18 +63,23 @@ def rows(
     Args:
         grouping_keys:
             Columns ids of grouping keys
-        preceding:
-            number of preceding rows to include. If None, include all preceding rows
+        start:
+            The window's starting boundary relative to the current row. For example, "-1" means one row prior
+            "1" means one row after, and "0" means the current row. If None, the window is unbounded from the start.
         following:
-            number of following rows to include. If None, include all following rows
+            The window's ending boundary relative to the current row. For example, "-1" means one row prior
+            "1" means one row after, and "0" means the current row. If None, the window is unbounded until the end.
         min_periods (int, default 0):
             Minimum number of input rows to generate output.
         ordering:
             Ordering to apply on top of based dataframe ordering
     Returns:
         WindowSpec
     """
-    bounds = RowsWindowBounds(preceding=preceding, following=following)
+    bounds = RowsWindowBounds(
+        start=start,
+        end=end,
+    )
     return WindowSpec(
         grouping_keys=tuple(map(ex.deref, grouping_keys)),
         bounds=bounds,
@@ -97,7 +102,7 @@ def cumulative_rows(
     Returns:
         WindowSpec
     """
-    bounds = RowsWindowBounds(following=0)
+    bounds = RowsWindowBounds(end=0)
     return WindowSpec(
         grouping_keys=tuple(map(ex.deref, grouping_keys)),
         bounds=bounds,
@@ -119,7 +124,7 @@ def inverse_cumulative_rows(
     Returns:
         WindowSpec
     """
-    bounds = RowsWindowBounds(preceding=0)
+    bounds = RowsWindowBounds(start=0)
     return WindowSpec(
         grouping_keys=tuple(map(ex.deref, grouping_keys)),
         bounds=bounds,
@@ -132,18 +137,35 @@ def inverse_cumulative_rows(
 
 @dataclass(frozen=True)
 class RowsWindowBounds:
-    preceding: Optional[int] = None
-    following: Optional[int] = None
-
+    start: Optional[int] = None
+    end: Optional[int] = None
 
-# TODO: Expand to datetime offsets
-OffsetType = Union[float, int]
+    def __post_init__(self):
+        if self.start is None:
+            return
+        if self.end is None:
+            return
+        if self.start > self.end:
+            raise ValueError(
+                f"Invalid window: start({self.start}) is greater than end({self.end})"
+            )
 
 
 @dataclass(frozen=True)
 class RangeWindowBounds:
-    preceding: Optional[OffsetType] = None
-    following: Optional[OffsetType] = None
+    # TODO(b/388916840) Support range rolling on timeseries with timedeltas.
+    start: Optional[int] = None
+    end: Optional[int] = None
+
+    def __post_init__(self):
+        if self.start is None:
+            return
+        if self.end is None:
+            return
+        if self.start > self.end:
+            raise ValueError(
+                f"Invalid window: start({self.start}) is greater than end({self.end})"
+            )
 
 
 @dataclass(frozen=True)

bigframes/dataframe.py

@@ -2428,12 +2428,12 @@ def replace(
 
     @validations.requires_ordering()
     def ffill(self, *, limit: typing.Optional[int] = None) -> DataFrame:
-        window = windows.rows(preceding=limit, following=0)
+        window = windows.rows(start=None if limit is None else -limit, end=0)
         return self._apply_window_op(agg_ops.LastNonNullOp(), window)
 
     @validations.requires_ordering()
     def bfill(self, *, limit: typing.Optional[int] = None) -> DataFrame:
-        window = windows.rows(preceding=0, following=limit)
+        window = windows.rows(start=0, end=limit)
         return self._apply_window_op(agg_ops.FirstNonNullOp(), window)
 
     def isin(self, values) -> DataFrame:
@@ -3310,7 +3310,7 @@ def _perform_join_by_index(
     def rolling(self, window: int, min_periods=None) -> bigframes.core.window.Window:
         # To get n size window, need current row and n-1 preceding rows.
         window_def = windows.rows(
-            preceding=window - 1, following=0, min_periods=min_periods or window
+            start=-(window - 1), end=0, min_periods=min_periods or window
         )
         return bigframes.core.window.Window(
             self._block, window_def, self._block.value_columns

bigframes/series.py

@@ -544,15 +544,15 @@ def cumsum(self) -> Series:
 
     @validations.requires_ordering()
     def ffill(self, *, limit: typing.Optional[int] = None) -> Series:
-        window = windows.rows(preceding=limit, following=0)
+        window = windows.rows(start=None if limit is None else -limit, end=0)
         return self._apply_window_op(agg_ops.LastNonNullOp(), window)
 
     pad = ffill
     pad.__doc__ = inspect.getdoc(vendored_pandas_series.Series.ffill)
 
     @validations.requires_ordering()
     def bfill(self, *, limit: typing.Optional[int] = None) -> Series:
-        window = windows.rows(preceding=0, following=limit)
+        window = windows.rows(start=0, end=limit)
         return self._apply_window_op(agg_ops.FirstNonNullOp(), window)
 
     @validations.requires_ordering()
@@ -1441,7 +1441,7 @@ def sort_index(self, *, axis=0, ascending=True, na_position="last") -> Series:
     def rolling(self, window: int, min_periods=None) -> bigframes.core.window.Window:
         # To get n size window, need current row and n-1 preceding rows.
         window_spec = windows.rows(
-            preceding=window - 1, following=0, min_periods=min_periods or window
+            start=-(window - 1), end=0, min_periods=min_periods or window
         )
         return bigframes.core.window.Window(
             self._block, window_spec, self._block.value_columns, is_series=True

tests/unit/core/test_windowspec.py

@@ -0,0 +1,29 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pytest
+
+from bigframes.core import window_spec
+
+
+@pytest.mark.parametrize(("start", "end"), [(-1, -2), (1, -2), (2, 1)])
+def test_invalid_rows_window_boundary_raise_error(start, end):
+    with pytest.raises(ValueError):
+        window_spec.RowsWindowBounds(start, end)
+
+
+@pytest.mark.parametrize(("start", "end"), [(-1, -2), (1, -2), (2, 1)])
+def test_invalid_range_window_boundary_raise_error(start, end):
+    with pytest.raises(ValueError):
+        window_spec.RangeWindowBounds(start, end)