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fix: bpd.merge on common columns #1905

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Merged
merged 1 commit into from
Jul 15, 2025
Merged

fix: bpd.merge on common columns #1905

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47 changes: 38 additions & 9 deletions bigframes/dataframe.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3434,15 +3434,9 @@ def merge(
)
return DataFrame(result_block)

if on is None:
if left_on is None or right_on is None:
raise ValueError("Must specify `on` or `left_on` + `right_on`.")
else:
if left_on is not None or right_on is not None:
raise ValueError(
"Can not pass both `on` and `left_on` + `right_on` params."
)
left_on, right_on = on, on
left_on, right_on = self._validate_left_right_on(
right, on, left_on=left_on, right_on=right_on
)

if utils.is_list_like(left_on):
left_on = list(left_on) # type: ignore
Expand Down Expand Up @@ -3479,6 +3473,41 @@ def merge(
)
return DataFrame(block)

def _validate_left_right_on(
self,
right: DataFrame,
on: Union[blocks.Label, Sequence[blocks.Label], None] = None,
*,
left_on: Union[blocks.Label, Sequence[blocks.Label], None] = None,
right_on: Union[blocks.Label, Sequence[blocks.Label], None] = None,
):
if on is not None:
if left_on is not None or right_on is not None:
raise ValueError(
"Can not pass both `on` and `left_on` + `right_on` params."
)
return on, on

if left_on is not None and right_on is not None:
return left_on, right_on

left_cols = self.columns
right_cols = right.columns
common_cols = left_cols.intersection(right_cols)
if len(common_cols) == 0:
raise ValueError(
"No common columns to perform merge on."
f"Merge options: left_on={left_on}, "
f"right_on={right_on}, "
)
if (
not left_cols.join(common_cols, how="inner").is_unique
or not right_cols.join(common_cols, how="inner").is_unique
):
raise ValueError(f"Data columns not unique: {repr(common_cols)}")

return common_cols, common_cols

def join(
self,
other: Union[DataFrame, bigframes.series.Series],
Expand Down
58 changes: 57 additions & 1 deletion tests/system/small/test_pandas.py
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Original file line number Diff line number Diff line change
Expand Up @@ -13,6 +13,7 @@
# limitations under the License.

from datetime import datetime
import re
import typing

import pandas as pd
Expand Down Expand Up @@ -343,7 +344,7 @@ def test_merge_left_on_right_on(scalars_dfs, merge_how):
assert_pandas_df_equal(bf_result, pd_result, ignore_order=True)


def test_pd_merge_cross(scalars_dfs):
def test_merge_cross(scalars_dfs):
scalars_df, scalars_pandas_df = scalars_dfs
left_columns = ["int64_col", "float64_col", "int64_too"]
right_columns = ["int64_col", "bool_col", "string_col", "rowindex_2"]
Expand Down Expand Up @@ -398,6 +399,61 @@ def test_merge_series(scalars_dfs, merge_how):
assert_pandas_df_equal(bf_result, pd_result, ignore_order=True)


def test_merge_w_common_columns(scalars_dfs):
scalars_df, scalars_pandas_df = scalars_dfs
left_columns = ["int64_col", "int64_too"]
right_columns = ["int64_col", "bool_col"]

df = bpd.merge(
scalars_df[left_columns], scalars_df[right_columns], "inner", sort=True
)

pd_result = pd.merge(
scalars_pandas_df[left_columns],
scalars_pandas_df[right_columns],
"inner",
sort=True,
)
assert_pandas_df_equal(df.to_pandas(), pd_result, ignore_order=True)


def test_merge_raises_error_when_no_common_columns(scalars_dfs):
scalars_df, _ = scalars_dfs
left_columns = ["float64_col", "int64_too"]
right_columns = ["int64_col", "bool_col"]

left = scalars_df[left_columns]
right = scalars_df[right_columns]

with pytest.raises(
ValueError,
match="No common columns to perform merge on.",
):
bpd.merge(left, right, "inner")


def test_merge_raises_error_when_left_right_on_set(scalars_dfs):
scalars_df, _ = scalars_dfs
left_columns = ["int64_col", "int64_too"]
right_columns = ["int64_col", "bool_col"]

left = scalars_df[left_columns]
right = scalars_df[right_columns]

with pytest.raises(
ValueError,
match=re.escape("Can not pass both `on` and `left_on` + `right_on` params."),
):
bpd.merge(
left,
right,
"inner",
left_on="int64_too",
right_on="int64_col",
on="int64_col",
)


def _convert_pandas_category(pd_s: pd.Series):
"""
Transforms a pandas Series with Categorical dtype into a bigframes-compatible
Expand Down