feat: to_gbq uses Parquet by default, use api_method="load_csv" for old behavior

CONTRIBUTING.rst

@@ -148,7 +148,7 @@ Running System Tests
 
   .. note::
 
-      System tests are only configured to run under Python 3.8 and 3.9.
+      System tests are only configured to run under Python 3.7, 3.8 and 3.9.
       For expediency, we do not run them in older versions of Python 3.
 
   This alone will not run the tests. You'll need to change some local

ci/requirements-3.7-0.23.2.conda

@@ -2,8 +2,9 @@ codecov
 coverage
 fastavro
 flake8
-numpy==1.14.5
+numpy==1.16.6
 google-cloud-bigquery==1.11.1
+pyarrow==3.0.0
 pydata-google-auth
 pytest
 pytest-cov

ci/requirements-3.9-NIGHTLY.conda

@@ -1,6 +1,7 @@
 pydata-google-auth
 google-cloud-bigquery
 google-cloud-bigquery-storage
+pyarrow
 pytest
 pytest-cov
 codecov

docs/install.rst

@@ -29,7 +29,7 @@ Install from Source
 
 .. code-block:: shell
 
-    $ pip install git+https://github.com/pydata/pandas-gbq.git
+    $ pip install git+https://github.com/googleapis/python-bigquery-pandas.git
 
 
 Dependencies
@@ -38,6 +38,7 @@ Dependencies
 This module requires following additional dependencies:
 
 - `pydata-google-auth <https://github.com/pydata/pydata-google-auth>`__: Helpers for authentication to Google's API
+- `pyarrow <https://arrow.apache.org/docs/python/>`__: Format for getting data to/from Google BigQuery
 - `google-auth <https://github.com/GoogleCloudPlatform/google-auth-library-python>`__: authentication and authorization for Google's API
 - `google-auth-oauthlib <https://github.com/GoogleCloudPlatform/google-auth-library-python-oauthlib>`__: integration with `oauthlib <https://github.com/idan/oauthlib>`__ for end-user authentication
 - `google-cloud-bigquery <https://googleapis.dev/python/bigquery/latest/index.html>`__: Google Cloud client library for BigQuery

noxfile.py

@@ -28,7 +28,7 @@
 BLACK_PATHS = ["docs", "pandas_gbq", "tests", "noxfile.py", "setup.py"]
 
 DEFAULT_PYTHON_VERSION = "3.8"
-SYSTEM_TEST_PYTHON_VERSIONS = ["3.8", "3.9"]
+SYSTEM_TEST_PYTHON_VERSIONS = ["3.7", "3.8", "3.9"]
 UNIT_TEST_PYTHON_VERSIONS = ["3.7", "3.8", "3.9"]
 
 CURRENT_DIRECTORY = pathlib.Path(__file__).parent.absolute()

owlbot.py

@@ -31,7 +31,7 @@
 extras = ["tqdm"]
 templated_files = common.py_library(
     unit_test_python_versions=["3.7", "3.8", "3.9"],
-    system_test_python_versions=["3.8", "3.9"],
+    system_test_python_versions=["3.7", "3.8", "3.9"],
     cov_level=86,
     unit_test_extras=extras,
     system_test_extras=extras,

pandas_gbq/exceptions.py

@@ -3,21 +3,30 @@
 # license that can be found in the LICENSE file.
 
 
+class GenericGBQException(ValueError):
+    """
+    Raised when an unrecognized Google API Error occurs.
+    """
+
+
 class AccessDenied(ValueError):
     """
     Raised when invalid credentials are provided, or tokens have expired.
     """
 
-    pass
+
+class ConversionError(GenericGBQException):
+    """
+    Raised when there is a problem converting the DataFrame to a format
+    required to upload it to BigQuery.
+    """
 
 
 class InvalidPrivateKeyFormat(ValueError):
     """
     Raised when provided private key has invalid format.
     """
 
-    pass
-
 
 class PerformanceWarning(RuntimeWarning):
     """

pandas_gbq/features.py

@@ -10,6 +10,7 @@
 BIGQUERY_BQSTORAGE_VERSION = "1.24.0"
 BIGQUERY_FROM_DATAFRAME_CSV_VERSION = "2.6.0"
 PANDAS_VERBOSITY_DEPRECATION_VERSION = "0.23.0"
+PANDAS_PARQUET_LOSSLESS_TIMESTAMP_VERSION = "1.1.0"
 
 
 class Features:
@@ -89,5 +90,14 @@ def pandas_has_deprecated_verbose(self):
         )
         return self.pandas_installed_version >= pandas_verbosity_deprecation
 
+    @property
+    def pandas_has_parquet_with_lossless_timestamp(self):
+        import pkg_resources
+
+        desired_version = pkg_resources.parse_version(
+            PANDAS_PARQUET_LOSSLESS_TIMESTAMP_VERSION
+        )
+        return self.pandas_installed_version >= desired_version
+
 
 FEATURES = Features()

pandas_gbq/gbq.py

@@ -18,8 +18,11 @@
     bigquery = None
     google_exceptions = None
 
-from pandas_gbq.exceptions import AccessDenied
-from pandas_gbq.exceptions import PerformanceWarning
+from pandas_gbq.exceptions import (
+    AccessDenied,
+    GenericGBQException,
+    PerformanceWarning,
+)
 from pandas_gbq import features
 from pandas_gbq.features import FEATURES
 import pandas_gbq.schema
@@ -69,14 +72,6 @@ class DatasetCreationError(ValueError):
     pass
 
 
-class GenericGBQException(ValueError):
-    """
-    Raised when an unrecognized Google API Error occurs.
-    """
-
-    pass
-
-
 class InvalidColumnOrder(ValueError):
     """
     Raised when the provided column order for output
@@ -520,7 +515,7 @@ def _download_results(
             df = rows_iter.to_dataframe(
                 dtypes=conversion_dtypes,
                 progress_bar_type=progress_bar_type,
-                **to_dataframe_kwargs
+                **to_dataframe_kwargs,
             )
         except self.http_error as ex:
             self.process_http_error(ex)
@@ -541,6 +536,7 @@ def load_data(
         chunksize=None,
         schema=None,
         progress_bar=True,
+        api_method: str = "load_parquet",
     ):
         from pandas_gbq import load
 
@@ -554,6 +550,7 @@ def load_data(
                 chunksize=chunksize,
                 schema=schema,
                 location=self.location,
+                api_method=api_method,
             )
             if progress_bar and tqdm:
                 chunks = tqdm.tqdm(chunks)
@@ -876,6 +873,7 @@ def to_gbq(
     location=None,
     progress_bar=True,
     credentials=None,
+    api_method: str = "default",
     verbose=None,
     private_key=None,
 ):
@@ -964,6 +962,12 @@ def to_gbq(
         :class:`google.oauth2.service_account.Credentials` directly.
 
         .. versionadded:: 0.8.0
+    api_method : str, optional
+        API method used to upload DataFrame to BigQuery. One of "load_parquet",
+        "load_csv". Default "load_parquet" if pandas is version 1.1.0+,
+        otherwise "load_csv".
+
+        .. versionadded:: 0.16.0
     verbose : bool, deprecated
         Deprecated in Pandas-GBQ 0.4.0. Use the `logging module
         to adjust verbosity instead
@@ -988,6 +992,28 @@ def to_gbq(
             stacklevel=1,
         )
 
+    if api_method == "default":
+        # Avoid using parquet if pandas doesn't support lossless conversions to
+        # parquet timestamp. See: https://stackoverflow.com/a/69758676/101923
+        if FEATURES.pandas_has_parquet_with_lossless_timestamp:
+            api_method = "load_parquet"
+        else:
+            api_method = "load_csv"
+
+    if chunksize is not None:
+        if api_method == "load_parquet":
+            warnings.warn(
+                "chunksize is ignored when using api_method='load_parquet'",
+                DeprecationWarning,
+                stacklevel=2,
+            )
+        elif api_method == "load_csv":
+            warnings.warn(
+                "chunksize will be ignored when using api_method='load_csv' in a future version of pandas-gbq",
+                PendingDeprecationWarning,
+                stacklevel=2,
+            )
+
     if if_exists not in ("fail", "replace", "append"):
         raise ValueError("'{0}' is not valid for if_exists".format(if_exists))
 
@@ -1071,6 +1097,7 @@ def to_gbq(
         chunksize=chunksize,
         schema=table_schema,
         progress_bar=progress_bar,
+        api_method=api_method,
     )