fix: Properly support format param for numerical input.

bigframes/core/compile/scalar_op_compiler.py

@@ -42,6 +42,8 @@
 
 # Datetime constants
 UNIT_TO_US_CONVERSION_FACTORS = {
+    "W": 7 * 24 * 60 * 60 * 1000 * 1000,
+    "d": 24 * 60 * 60 * 1000 * 1000,
     "D": 24 * 60 * 60 * 1000 * 1000,
     "h": 60 * 60 * 1000 * 1000,
     "m": 60 * 1000 * 1000,
@@ -733,12 +735,19 @@ def to_datetime_op_impl(x: ibis_types.Value, op: ops.ToDatetimeOp):
     if x.type() == ibis_dtypes.str:
         x = x.to_timestamp(op.format) if op.format else timestamp(x)
     elif x.type() == ibis_dtypes.Timestamp(timezone="UTC"):
+        if op.format:
+            raise NotImplementedError(
+                f"Format parameter is not supported for Timestamp input types. {constants.FEEDBACK_LINK}"
+            )
         return x
     elif x.type() != ibis_dtypes.timestamp:
-        # The default unit is set to "ns" (nanoseconds) for consistency
-        # with pandas, where "ns" is the default unit for datetime operations.
-        unit = op.unit or "ns"
-        x = numeric_to_datatime(x, unit)
+        if op.format:
+            x = x.cast(ibis_dtypes.str).to_timestamp(op.format)
+        else:
+            # The default unit is set to "ns" (nanoseconds) for consistency
+            # with pandas, where "ns" is the default unit for datetime operations.
+            unit = op.unit or "ns"
+            x = numeric_to_datatime(x, unit)
 
     return x.cast(ibis_dtypes.Timestamp(timezone="UTC" if op.utc else None))
 

bigframes/core/tools/datetimes.py

@@ -73,6 +73,14 @@ def to_datetime(
             f"String and Timestamp requires utc=True. {constants.FEEDBACK_LINK}"
         )
 
+    if format and unit and arg.dtype in ("Int64", "Float64"):  # type: ignore
+        raise ValueError("cannot specify both format and unit")
+
+    if unit and arg.dtype not in ("Int64", "Float64"):  # type: ignore
+        raise NotImplementedError(
+            f"Unit parameter is not supported for non-numerical input types. {constants.FEEDBACK_LINK}"
+        )
+
     return arg._apply_unary_op(  # type: ignore
         ops.ToDatetimeOp(
             utc=utc,

tests/system/small/test_pandas.py

@@ -539,3 +539,46 @@ def test_to_datetime_series(scalars_dfs):
     pd.testing.assert_series_equal(
         bf_result, pd_result, check_index_type=False, check_names=False
     )
+
+
+@pytest.mark.parametrize(
+    ("arg", "unit"),
+    [
+        ([1, 2, 3], "W"),
+        ([1, 2, 3], "d"),
+        ([1, 2, 3], "D"),
+        ([1, 2, 3], "h"),
+        ([1, 2, 3], "m"),
+        ([20242330, 25244685, 34324234], "s"),
+        ([20242330000, 25244685000, 34324234000], "ms"),
+        ([20242330000000, 25244685000000, 34324234000000], "us"),
+        ([20242330000000000, 25244685000000000, 34324234000000000], "ns"),
+    ],
+)
+def test_to_datetime_unit_param(arg, unit):
+    bf_result = bpd.to_datetime(arg, unit=unit).to_pandas().astype("datetime64[ns]")
+    pd_result = pd.Series(pd.to_datetime(arg, unit=unit)).dt.floor("us")
+    pd.testing.assert_series_equal(
+        bf_result, pd_result, check_index_type=False, check_names=False
+    )
+
+
+@pytest.mark.parametrize(
+    ("arg", "utc", "format"),
+    [
+        ([20230110, 20230101, 20230101], False, "%Y%m%d"),
+        ([201301.01], False, "%Y%m.%d"),
+        (["2023-01-10", "2023-01-20", "2023-01-01"], True, "%Y-%m-%d"),
+        (["2014-08-15 07:19"], True, "%Y-%m-%d %H:%M"),
+    ],
+)
+def test_to_datetime_format_param(arg, utc, format):
+    bf_result = (
+        bpd.to_datetime(arg, utc=utc, format=format)
+        .to_pandas()
+        .astype("datetime64[ns, UTC]" if utc else "datetime64[ns]")
+    )
+    pd_result = pd.Series(pd.to_datetime(arg, utc=utc, format=format)).dt.floor("us")
+    pd.testing.assert_series_equal(
+        bf_result, pd_result, check_index_type=False, check_names=False
+    )