feat: accepts a table ID, which downloads the table without a query (#…

…443)

Thank you for opening a Pull Request! Before submitting your PR, there are a few things you can do to make sure it goes smoothly:
- [x] Make sure to open an issue as a [bug/issue](https://github.com/googleapis/python-bigquery-pandas/issues/new/choose) before writing your code!  That way we can discuss the change, evaluate designs, and agree on the general idea
- [x] Ensure the tests and linter pass
- [x] Code coverage does not decrease (if any source code was changed)
- [x] Appropriate docs were updated (if necessary)

Fixes #266  🦕

.coveragerc

@@ -22,7 +22,7 @@ omit =
   google/cloud/__init__.py
 
 [report]
-fail_under = 88
+fail_under = 89
 show_missing = True
 exclude_lines =
     # Re-enable the standard pragma

noxfile.py

@@ -259,7 +259,7 @@ def cover(session):
     test runs (not system test runs), and then erases coverage data.
     """
     session.install("coverage", "pytest-cov")
-    session.run("coverage", "report", "--show-missing", "--fail-under=88")
+    session.run("coverage", "report", "--show-missing", "--fail-under=89")
 
     session.run("coverage", "erase")
 

owlbot.py

@@ -33,7 +33,7 @@
 templated_files = common.py_library(
     unit_test_python_versions=["3.7", "3.8", "3.9", "3.10"],
     system_test_python_versions=["3.7", "3.8", "3.9", "3.10"],
-    cov_level=88,
+    cov_level=89,
     unit_test_extras=extras,
     system_test_extras=extras,
     intersphinx_dependencies={

pandas_gbq/gbq.py

@@ -3,12 +3,21 @@
 # license that can be found in the LICENSE file.
 
 import logging
+import re
 import time
 import warnings
 from datetime import datetime
+import typing
+from typing import Any, Dict, Optional, Union
 
 import numpy as np
 
+# Only import at module-level at type checking time to avoid circular
+# dependencies in the pandas package, which has an optional dependency on
+# pandas-gbq.
+if typing.TYPE_CHECKING:  # pragma: NO COVER
+    import pandas
+
 # Required dependencies, but treat as optional so that _test_google_api_imports
 # can provide a better error message.
 try:
@@ -64,6 +73,10 @@ def _test_google_api_imports():
         raise ImportError("pandas-gbq requires google-cloud-bigquery") from ex
 
 
+def _is_query(query_or_table: str) -> bool:
+    return re.search(r"\s", query_or_table.strip(), re.MULTILINE) is not None
+
+
 class DatasetCreationError(ValueError):
     """
     Raised when the create dataset method fails
@@ -374,6 +387,30 @@ def process_http_error(ex):
 
         raise GenericGBQException("Reason: {0}".format(ex))
 
+    def download_table(
+        self,
+        table_id: str,
+        max_results: Optional[int] = None,
+        progress_bar_type: Optional[str] = None,
+        dtypes: Optional[Dict[str, Union[str, Any]]] = None,
+    ) -> "pandas.DataFrame":
+        self._start_timer()
+
+        try:
+            table_ref = bigquery.TableReference.from_string(
+                table_id, default_project=self.project_id
+            )
+            rows_iter = self.client.list_rows(table_ref, max_results=max_results)
+        except self.http_error as ex:
+            self.process_http_error(ex)
+
+        return self._download_results(
+            rows_iter,
+            max_results=max_results,
+            progress_bar_type=progress_bar_type,
+            user_dtypes=dtypes,
+        )
+
     def run_query(self, query, max_results=None, progress_bar_type=None, **kwargs):
         from concurrent.futures import TimeoutError
         from google.auth.exceptions import RefreshError
@@ -390,15 +427,6 @@ def run_query(self, query, max_results=None, progress_bar_type=None, **kwargs):
         if config is not None:
             job_config.update(config)
 
-            if "query" in config and "query" in config["query"]:
-                if query is not None:
-                    raise ValueError(
-                        "Query statement can't be specified "
-                        "inside config while it is specified "
-                        "as parameter"
-                    )
-                query = config["query"].pop("query")
-
         self._start_timer()
 
         try:
@@ -464,15 +492,25 @@ def run_query(self, query, max_results=None, progress_bar_type=None, **kwargs):
             )
 
         dtypes = kwargs.get("dtypes")
+
+        # Ensure destination is populated.
+        try:
+            query_reply.result()
+        except self.http_error as ex:
+            self.process_http_error(ex)
+
+        rows_iter = self.client.list_rows(
+            query_reply.destination, max_results=max_results
+        )
         return self._download_results(
-            query_reply,
+            rows_iter,
             max_results=max_results,
             progress_bar_type=progress_bar_type,
             user_dtypes=dtypes,
         )
 
     def _download_results(
-        self, query_job, max_results=None, progress_bar_type=None, user_dtypes=None,
+        self, rows_iter, max_results=None, progress_bar_type=None, user_dtypes=None,
     ):
         # No results are desired, so don't bother downloading anything.
         if max_results == 0:
@@ -504,11 +542,6 @@ def _download_results(
             to_dataframe_kwargs["create_bqstorage_client"] = create_bqstorage_client
 
         try:
-            query_job.result()
-            # Get the table schema, so that we can list rows.
-            destination = self.client.get_table(query_job.destination)
-            rows_iter = self.client.list_rows(destination, max_results=max_results)
-
             schema_fields = [field.to_api_repr() for field in rows_iter.schema]
             conversion_dtypes = _bqschema_to_nullsafe_dtypes(schema_fields)
             conversion_dtypes.update(user_dtypes)
@@ -644,7 +677,7 @@ def _cast_empty_df_dtypes(schema_fields, df):
 
 
 def read_gbq(
-    query,
+    query_or_table,
     project_id=None,
     index_col=None,
     col_order=None,
@@ -668,17 +701,18 @@ def read_gbq(
 
     This method uses the Google Cloud client library to make requests to
     Google BigQuery, documented `here
-    <https://google-cloud-python.readthedocs.io/en/latest/bigquery/usage.html>`__.
+    <https://googleapis.dev/python/bigquery/latest/index.html>`__.
 
     See the :ref:`How to authenticate with Google BigQuery <authentication>`
     guide for authentication instructions.
 
     Parameters
     ----------
-    query : str
-        SQL-Like Query to return data values.
+    query_or_table : str
+        SQL query to return data values. If the string is a table ID, fetch the
+        rows directly from the table without running a query.
     project_id : str, optional
-        Google BigQuery Account project ID. Optional when available from
+        Google Cloud Platform project ID. Optional when available from
         the environment.
     index_col : str, optional
         Name of result column to use for index in results DataFrame.
@@ -688,14 +722,14 @@ def read_gbq(
     reauth : boolean, default False
         Force Google BigQuery to re-authenticate the user. This is useful
         if multiple accounts are used.
-    auth_local_webserver : boolean, default False
-        Use the `local webserver flow`_ instead of the `console flow`_
-        when getting user credentials.
-
-        .. _local webserver flow:
-            http://google-auth-oauthlib.readthedocs.io/en/latest/reference/google_auth_oauthlib.flow.html#google_auth_oauthlib.flow.InstalledAppFlow.run_local_server
-        .. _console flow:
-            http://google-auth-oauthlib.readthedocs.io/en/latest/reference/google_auth_oauthlib.flow.html#google_auth_oauthlib.flow.InstalledAppFlow.run_console
+    auth_local_webserver : bool, default False
+        Use the `local webserver flow
+        <https://googleapis.dev/python/google-auth-oauthlib/latest/reference/google_auth_oauthlib.flow.html#google_auth_oauthlib.flow.InstalledAppFlow.run_local_server>`_
+        instead of the `console flow
+        <https://googleapis.dev/python/google-auth-oauthlib/latest/reference/google_auth_oauthlib.flow.html#google_auth_oauthlib.flow.InstalledAppFlow.run_console>`_
+        when getting user credentials. Your code must run on the same machine
+        as your web browser and your web browser can access your application
+        via ``localhost:808X``.
 
         .. versionadded:: 0.2.0
     dialect : str, default 'standard'
@@ -745,13 +779,6 @@ def read_gbq(
         <https://cloud.google.com/bigquery/docs/access-control#roles>`__
         permission on the project you are billing queries to.
 
-        **Note:** Due to a `known issue in the ``google-cloud-bigquery``
-        package
-        <https://github.com/googleapis/google-cloud-python/pull/7633>`__
-        (fixed in version 1.11.0), you must write your query results to a
-        destination table. To do this with ``read_gbq``, supply a
-        ``configuration`` dictionary.
-
         This feature requires the ``google-cloud-bigquery-storage`` and
         ``pyarrow`` packages.
 
@@ -823,6 +850,15 @@ def read_gbq(
     if dialect not in ("legacy", "standard"):
         raise ValueError("'{0}' is not valid for dialect".format(dialect))
 
+    if configuration and "query" in configuration and "query" in configuration["query"]:
+        if query_or_table is not None:
+            raise ValueError(
+                "Query statement can't be specified "
+                "inside config while it is specified "
+                "as parameter"
+            )
+        query_or_table = configuration["query"].pop("query")
+
     connector = GbqConnector(
         project_id,
         reauth=reauth,
@@ -834,13 +870,21 @@ def read_gbq(
         use_bqstorage_api=use_bqstorage_api,
     )
 
-    final_df = connector.run_query(
-        query,
-        configuration=configuration,
-        max_results=max_results,
-        progress_bar_type=progress_bar_type,
-        dtypes=dtypes,
-    )
+    if _is_query(query_or_table):
+        final_df = connector.run_query(
+            query_or_table,
+            configuration=configuration,
+            max_results=max_results,
+            progress_bar_type=progress_bar_type,
+            dtypes=dtypes,
+        )
+    else:
+        final_df = connector.download_table(
+            query_or_table,
+            max_results=max_results,
+            progress_bar_type=progress_bar_type,
+            dtypes=dtypes,
+        )
 
     # Reindex the DataFrame on the provided column
     if index_col is not None:
@@ -889,7 +933,7 @@ def to_gbq(
 
     This method uses the Google Cloud client library to make requests to
     Google BigQuery, documented `here
-    <https://google-cloud-python.readthedocs.io/en/latest/bigquery/usage.html>`__.
+    <https://googleapis.dev/python/bigquery/latest/index.html>`__.
 
     See the :ref:`How to authenticate with Google BigQuery <authentication>`
     guide for authentication instructions.
@@ -902,7 +946,7 @@ def to_gbq(
         Name of table to be written, in the form ``dataset.tablename`` or
         ``project.dataset.tablename``.
     project_id : str, optional
-        Google BigQuery Account project ID. Optional when available from
+        Google Cloud Platform project ID. Optional when available from
         the environment.
     chunksize : int, optional
         Number of rows to be inserted in each chunk from the dataframe.
@@ -920,13 +964,13 @@ def to_gbq(
         ``'append'``
             If table exists, insert data. Create if does not exist.
     auth_local_webserver : bool, default False
-        Use the `local webserver flow`_ instead of the `console flow`_
-        when getting user credentials.
-
-        .. _local webserver flow:
-            http://google-auth-oauthlib.readthedocs.io/en/latest/reference/google_auth_oauthlib.flow.html#google_auth_oauthlib.flow.InstalledAppFlow.run_local_server
-        .. _console flow:
-            http://google-auth-oauthlib.readthedocs.io/en/latest/reference/google_auth_oauthlib.flow.html#google_auth_oauthlib.flow.InstalledAppFlow.run_console
+        Use the `local webserver flow
+        <https://googleapis.dev/python/google-auth-oauthlib/latest/reference/google_auth_oauthlib.flow.html#google_auth_oauthlib.flow.InstalledAppFlow.run_local_server>`_
+        instead of the `console flow
+        <https://googleapis.dev/python/google-auth-oauthlib/latest/reference/google_auth_oauthlib.flow.html#google_auth_oauthlib.flow.InstalledAppFlow.run_console>`_
+        when getting user credentials. Your code must run on the same machine
+        as your web browser and your web browser can access your application
+        via ``localhost:808X``.
 
         .. versionadded:: 0.2.0
     table_schema : list of dicts, optional

pandas_gbq/timestamp.py

@@ -7,6 +7,8 @@
 Private module.
 """
 
+import pandas.api.types
+
 
 def localize_df(df, schema_fields):
     """Localize any TIMESTAMP columns to tz-aware type.
@@ -38,7 +40,11 @@ def localize_df(df, schema_fields):
         if "mode" in field and field["mode"].upper() == "REPEATED":
             continue
 
-        if field["type"].upper() == "TIMESTAMP" and df[column].dt.tz is None:
+        if (
+            field["type"].upper() == "TIMESTAMP"
+            and pandas.api.types.is_datetime64_ns_dtype(df.dtypes[column])
+            and df[column].dt.tz is None
+        ):
             df[column] = df[column].dt.tz_localize("UTC")
 
     return df

tests/system/conftest.py

@@ -3,6 +3,7 @@
 # license that can be found in the LICENSE file.
 
 import os
+import functools
 import pathlib
 
 from google.cloud import bigquery
@@ -56,6 +57,24 @@ def project(project_id):
     return project_id
 
 
+@pytest.fixture
+def to_gbq(credentials, project_id):
+    import pandas_gbq
+
+    return functools.partial(
+        pandas_gbq.to_gbq, project_id=project_id, credentials=credentials
+    )
+
+
+@pytest.fixture
+def read_gbq(credentials, project_id):
+    import pandas_gbq
+
+    return functools.partial(
+        pandas_gbq.read_gbq, project_id=project_id, credentials=credentials
+    )
+
+
 @pytest.fixture()
 def random_dataset_id(bigquery_client: bigquery.Client, project_id: str):
     dataset_id = prefixer.create_prefix()