docs(bigquery): add sample to read from query destination table

bigquery/samples/query_pagination.py

@@ -0,0 +1,53 @@
+# Copyright 2019 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+def query_pagination(client):
+
+ # [START bigquery_query_pagination]
+ # TODO(developer): Import the client library.
+ # from google.cloud import bigquery
+
+ # TODO(developer): Construct a BigQuery client object.
+ # client = bigquery.Client()
+
+ query = """
+ SELECT name, SUM(number) as total_people
+ FROM `bigquery-public-data.usa_names.usa_1910_2013`
+ GROUP BY name
+ ORDER BY total_people DESC
+ """
+ query_job = client.query(query) # Make an API request.
+ query_job.result() # Wait for the query to complete.
+
+ # Get the destination table for the query results.
+ #
+ # All queries write to a destination table. If a destination table is not
+ # specified, the BigQuery populates it with a reference to a temporary
+ # anonymous table after the query completes.
+ destination = query_job.destination
+
+ # Get the schema (and other properties) for the destination table.
+ #
+ # A schema is useful for converting from BigQuery types to Python types.
+ destination = client.get_table(destination)
+
+ # Download rows.
+ #
+ # The client library automatically handles pagination.
+ print("The query data:")
+ rows = client.list_rows(destination, max_results=20)
+ for row in rows:
+ print("name={}, count={}".format(row["name"], row["total_people"]))
+ # [END bigquery_query_pagination]

bigquery/samples/tests/test_query_pagination.py

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+# Copyright 2019 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from .. import query_pagination
+
+
+def test_query_pagination(capsys, client):
+
+ query_pagination.query_pagination(client)
+ out, _ = capsys.readouterr()
+ assert "The query data:" in out
+ assert "name=James, count=4942431" in out