fix!: to_gbq loads unit8 columns to BigQuery INT64 instead of STRING

noxfile.py

@@ -51,6 +51,7 @@
 UNIT_TEST_EXTRAS = [
     "bqstorage",
     "tqdm",
+    "geopandas",
 ]
 UNIT_TEST_EXTRAS_BY_PYTHON = {
     "3.9": [],

owlbot.py

@@ -32,7 +32,7 @@
     # Use a middle version of Python to test when no extras are installed.
     "3.9": []
 }
-extras = ["tqdm"]
+extras = ["tqdm", "geopandas"]
 templated_files = common.py_library(
     unit_test_python_versions=["3.8", "3.9", "3.10", "3.11", "3.12"],
     system_test_python_versions=["3.8", "3.9", "3.10", "3.11", "3.12"],

pandas_gbq/core/__init__.py

@@ -0,0 +1,3 @@
+# Copyright (c) 2024 pandas-gbq Authors All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.

pandas_gbq/core/pandas.py

@@ -0,0 +1,70 @@
+# Copyright (c) 2019 pandas-gbq Authors All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+import itertools
+
+import pandas
+
+
+def list_columns_and_indexes(dataframe, index=True):
+    """Return all index and column names with dtypes.
+
+    Returns:
+        Sequence[Tuple[str, dtype]]:
+            Returns a sorted list of indexes and column names with
+            corresponding dtypes. If an index is missing a name or has the
+            same name as a column, the index is omitted.
+    """
+    column_names = frozenset(dataframe.columns)
+    columns_and_indexes = []
+    if index:
+        if isinstance(dataframe.index, pandas.MultiIndex):
+            for name in dataframe.index.names:
+                if name and name not in column_names:
+                    values = dataframe.index.get_level_values(name)
+                    columns_and_indexes.append((name, values.dtype))
+        else:
+            if dataframe.index.name and dataframe.index.name not in column_names:
+                columns_and_indexes.append(
+                    (dataframe.index.name, dataframe.index.dtype)
+                )
+
+    columns_and_indexes += zip(dataframe.columns, dataframe.dtypes)
+    return columns_and_indexes
+
+
+def first_valid(series):
+    first_valid_index = series.first_valid_index()
+    if first_valid_index is not None:
+        return series.at[first_valid_index]
+
+
+def first_array_valid(series):
+    """Return the first "meaningful" element from the array series.
+
+    Here, "meaningful" means the first non-None element in one of the arrays that can
+    be used for type detextion.
+    """
+    first_valid_index = series.first_valid_index()
+    if first_valid_index is None:
+        return None
+
+    valid_array = series.at[first_valid_index]
+    valid_item = next((item for item in valid_array if not pandas.isna(item)), None)
+
+    if valid_item is not None:
+        return valid_item
+
+    # Valid item is None because all items in the "valid" array are invalid. Try
+    # to find a true valid array manually.
+    for array in itertools.islice(series, first_valid_index + 1, None):
+        try:
+            array_iter = iter(array)
+        except TypeError:
+            continue  # Not an array, apparently, e.g. None, thus skip.
+        valid_item = next((item for item in array_iter if not pandas.isna(item)), None)
+        if valid_item is not None:
+            break
+
+    return valid_item

pandas_gbq/gbq.py

@@ -25,6 +25,7 @@
 from pandas_gbq.features import FEATURES
 import pandas_gbq.query
 import pandas_gbq.schema
+import pandas_gbq.schema.pandas_to_bigquery
 import pandas_gbq.timestamp
 
 try:
@@ -1219,9 +1220,16 @@ def _generate_bq_schema(df, default_type="STRING"):
     be overridden: https://github.com/pydata/pandas-gbq/issues/218, this
     method can be removed after there is time to migrate away from this
     method."""
-    from pandas_gbq import schema
+    fields = pandas_gbq.schema.pandas_to_bigquery.dataframe_to_bigquery_fields(
+        df,
+        default_type=default_type,
+    )
+    fields_json = []
+
+    for field in fields:
+        fields_json.append(field.to_api_repr())
 
-    return schema.generate_bq_schema(df, default_type=default_type)
+    return {"fields": fields_json}
 
 
 class _Table(GbqConnector):

pandas_gbq/load.py

@@ -15,6 +15,8 @@
 
 from pandas_gbq import exceptions
 import pandas_gbq.schema
+import pandas_gbq.schema.bigquery
+import pandas_gbq.schema.pandas_to_bigquery
 
 
 def encode_chunk(dataframe):
@@ -214,11 +216,9 @@ def load_csv_from_file(
     This method is needed for writing with google-cloud-bigquery versions that
     don't implment load_table_from_dataframe with the CSV serialization format.
     """
-    if schema is None:
-        schema = pandas_gbq.schema.generate_bq_schema(dataframe)
-
-    schema = pandas_gbq.schema.remove_policy_tags(schema)
-    bq_schema = pandas_gbq.schema.to_google_cloud_bigquery(schema)
+    bq_schema = pandas_gbq.schema.pandas_to_bigquery.dataframe_to_bigquery_fields(
+        dataframe, schema
+    )
 
     def load_chunk(chunk, job_config):
         try:

pandas_gbq/schema.py → pandas_gbq/schema/__init__.py

@@ -92,37 +92,6 @@ def schema_is_subset(schema_remote, schema_local):
     return all(field in fields_remote for field in fields_local)
 
 
-def generate_bq_schema(dataframe, default_type="STRING"):
-    """Given a passed dataframe, generate the associated Google BigQuery schema.
-
-    Arguments:
-        dataframe (pandas.DataFrame): D
-    default_type : string
-        The default big query type in case the type of the column
-        does not exist in the schema.
-    """
-
-    # If you update this mapping, also update the table at
-    # `docs/source/writing.rst`.
-    type_mapping = {
-        "i": "INTEGER",
-        "b": "BOOLEAN",
-        "f": "FLOAT",
-        "O": "STRING",
-        "S": "STRING",
-        "U": "STRING",
-        "M": "TIMESTAMP",
-    }
-
-    fields = []
-    for column_name, dtype in dataframe.dtypes.items():
-        fields.append(
-            {"name": column_name, "type": type_mapping.get(dtype.kind, default_type)}
-        )
-
-    return {"fields": fields}
-
-
 def update_schema(schema_old, schema_new):
     """
     Given an old BigQuery schema, update it with a new one.

pandas_gbq/schema/bigquery.py

@@ -0,0 +1,44 @@
+# Copyright (c) 2019 pandas-gbq Authors All rights reserved.
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file.
+
+import collections
+
+import google.cloud.bigquery
+
+
+def to_schema_fields(schema):
+    """Coerce `schema` to a list of schema field instances.
+
+    Args:
+        schema(Sequence[Union[ \
+            :class:`~google.cloud.bigquery.schema.SchemaField`, \
+            Mapping[str, Any] \
+        ]]):
+            Table schema to convert. If some items are passed as mappings,
+            their content must be compatible with
+            :meth:`~google.cloud.bigquery.schema.SchemaField.from_api_repr`.
+
+    Returns:
+        Sequence[:class:`~google.cloud.bigquery.schema.SchemaField`]
+
+    Raises:
+        Exception: If ``schema`` is not a sequence, or if any item in the
+        sequence is not a :class:`~google.cloud.bigquery.schema.SchemaField`
+        instance or a compatible mapping representation of the field.
+    """
+    for field in schema:
+        if not isinstance(
+            field, (google.cloud.bigquery.SchemaField, collections.abc.Mapping)
+        ):
+            raise ValueError(
+                "Schema items must either be fields or compatible "
+                "mapping representations."
+            )
+
+    return [
+        field
+        if isinstance(field, google.cloud.bigquery.SchemaField)
+        else google.cloud.bigquery.SchemaField.from_api_repr(field)
+        for field in schema
+    ]