From 20a0768e80967c54fee72a355937dd7773fa05cc Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Wed, 15 Oct 2025 15:16:28 +0000
Subject: [PATCH 1/2] feat: Allow loading a DataFrame with a subset of BigQuery
 columns

This change modifies the behavior when a DataFrame is loaded to BigQuery with a schema that contains fields not present in the DataFrame.

Instead of raising a `ValueError`, a `UserWarning` is now issued, and the extra fields are appended to the schema. This allows for more flexible data loading scenarios.
---
 pandas_gbq/schema/pandas_to_bigquery.py      | 14 +++++----
 tests/unit/schema/test_pandas_to_bigquery.py | 33 +++++++++++++++-----
 2 files changed, 34 insertions(+), 13 deletions(-)

diff --git a/pandas_gbq/schema/pandas_to_bigquery.py b/pandas_gbq/schema/pandas_to_bigquery.py
index 5afae356..f2a56f52 100644
--- a/pandas_gbq/schema/pandas_to_bigquery.py
+++ b/pandas_gbq/schema/pandas_to_bigquery.py
@@ -139,14 +139,16 @@ def dataframe_to_bigquery_fields(
         bq_schema_out.append(bq_field)
         unknown_type_fields.append(bq_field)
 
-    # Catch any schema mismatch. The developer explicitly asked to serialize a
-    # column, but it was not found.
+    # Append any fields from the BigQuery schema that are not in the
+    # DataFrame.
     if override_fields_unused:
-        raise ValueError(
-            "Provided BigQuery fields contain field(s) not present in DataFrame: {}".format(
-                override_fields_unused
-            )
+        warnings.warn(
+            "Provided BigQuery fields contain field(s) not present in "
+            "DataFrame: {}".format(sorted(override_fields_unused)),
+            UserWarning,
         )
+        for field_name in sorted(override_fields_unused):
+            bq_schema_out.append(override_fields_by_name[field_name])
 
     # If schema detection was not successful for all columns, also try with
     # pyarrow, if available.
diff --git a/tests/unit/schema/test_pandas_to_bigquery.py b/tests/unit/schema/test_pandas_to_bigquery.py
index f3c4410b..fcba213e 100644
--- a/tests/unit/schema/test_pandas_to_bigquery.py
+++ b/tests/unit/schema/test_pandas_to_bigquery.py
@@ -179,16 +179,35 @@ def test_dataframe_to_bigquery_fields_fallback_needed_w_pyarrow(module_under_tes
 
 
 def test_dataframe_to_bigquery_fields_w_extra_fields(module_under_test):
-    with pytest.raises(ValueError) as exc_context:
-        module_under_test.dataframe_to_bigquery_fields(
-            pandas.DataFrame(),
-            override_bigquery_fields=(schema.SchemaField("not_in_df", "STRING"),),
+    dataframe = pandas.DataFrame({"in_df": [1, 2, 3]})
+    bq_schema = (
+        schema.SchemaField("in_df", "INTEGER"),
+        schema.SchemaField("not_in_df", "STRING"),
+        schema.SchemaField("also_not_in_df", "INTEGER"),
+    )
+
+    with pytest.warns(UserWarning) as record:
+        returned_schema = module_under_test.dataframe_to_bigquery_fields(
+            dataframe, override_bigquery_fields=bq_schema
         )
-    message = str(exc_context.value)
+
+    assert len(record) == 1
+    message = str(record[0].message)
     assert (
-        "Provided BigQuery fields contain field(s) not present in DataFrame:" in message
+        "Provided BigQuery fields contain field(s) not present in DataFrame"
+        in message
     )
-    assert "not_in_df" in message
+    # Note: The field names are sorted in the warning message.
+    assert "['also_not_in_df', 'not_in_df']" in message
+
+    expected_schema = (
+        schema.SchemaField("in_df", "INTEGER"),
+        # Note: The fields are sorted by name as they are added from the set of
+        # unused fields.
+        schema.SchemaField("also_not_in_df", "INTEGER"),
+        schema.SchemaField("not_in_df", "STRING"),
+    )
+    assert returned_schema == expected_schema
 
 
 def test_dataframe_to_bigquery_fields_geography(module_under_test):

From 1d15e16dd1b6755c366574bf6091c7a214a6ed77 Mon Sep 17 00:00:00 2001
From: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Date: Wed, 15 Oct 2025 16:24:23 +0000
Subject: [PATCH 2/2] =?UTF-8?q?=F0=9F=A6=89=20Updates=20from=20OwlBot=20po?=
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MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md
---
 tests/unit/schema/test_pandas_to_bigquery.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/tests/unit/schema/test_pandas_to_bigquery.py b/tests/unit/schema/test_pandas_to_bigquery.py
index fcba213e..4f3be85c 100644
--- a/tests/unit/schema/test_pandas_to_bigquery.py
+++ b/tests/unit/schema/test_pandas_to_bigquery.py
@@ -194,8 +194,7 @@ def test_dataframe_to_bigquery_fields_w_extra_fields(module_under_test):
     assert len(record) == 1
     message = str(record[0].message)
     assert (
-        "Provided BigQuery fields contain field(s) not present in DataFrame"
-        in message
+        "Provided BigQuery fields contain field(s) not present in DataFrame" in message
     )
     # Note: The field names are sorted in the warning message.
     assert "['also_not_in_df', 'not_in_df']" in message