File size: 4,960 Bytes
1856027 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 | # Copyright 2017 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
#
# http://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.
"""Connection for the Google BigQuery DB-API."""
import weakref
from google.cloud import bigquery
from google.cloud.bigquery.dbapi import cursor
from google.cloud.bigquery.dbapi import _helpers
@_helpers.raise_on_closed("Operating on a closed connection.")
class Connection(object):
"""DB-API Connection to Google BigQuery.
Args:
client (Optional[google.cloud.bigquery.Client]):
A REST API client used to connect to BigQuery. If not passed, a
client is created using default options inferred from the environment.
bqstorage_client(\
Optional[google.cloud.bigquery_storage_v1.BigQueryReadClient] \
):
A client that uses the faster BigQuery Storage API to fetch rows from
BigQuery. If not passed, it is created using the same credentials
as ``client`` (provided that BigQuery Storage dependencies are installed).
prefer_bqstorage_client (Optional[bool]):
Prefer the BigQuery Storage client over the REST client. If Storage
client isn't available, fall back to the REST client. Defaults to
``True``.
"""
def __init__(
self,
client=None,
bqstorage_client=None,
prefer_bqstorage_client=True,
):
if client is None:
client = bigquery.Client()
self._owns_client = True
else:
self._owns_client = False
# A warning is already raised by the BQ Storage client factory factory if
# instantiation fails, or if the given BQ Storage client instance is outdated.
if not prefer_bqstorage_client:
bqstorage_client = None
self._owns_bqstorage_client = False
elif bqstorage_client is None:
bqstorage_client = client._ensure_bqstorage_client()
self._owns_bqstorage_client = bqstorage_client is not None
else:
self._owns_bqstorage_client = False
bqstorage_client = client._ensure_bqstorage_client(bqstorage_client)
self._client = client
self._bqstorage_client = bqstorage_client
self._closed = False
self._cursors_created = weakref.WeakSet()
def close(self):
"""Close the connection and any cursors created from it.
Any BigQuery clients explicitly passed to the constructor are *not*
closed, only those created by the connection instance itself.
"""
self._closed = True
if self._owns_client:
self._client.close()
if self._owns_bqstorage_client:
# There is no close() on the BQ Storage client itself.
self._bqstorage_client._transport.grpc_channel.close()
for cursor_ in self._cursors_created:
if not cursor_._closed:
cursor_.close()
def commit(self):
"""No-op, but for consistency raise an error if connection is closed."""
def cursor(self):
"""Return a new cursor object.
Returns:
google.cloud.bigquery.dbapi.Cursor: A DB-API cursor that uses this connection.
"""
new_cursor = cursor.Cursor(self)
self._cursors_created.add(new_cursor)
return new_cursor
def connect(client=None, bqstorage_client=None, prefer_bqstorage_client=True):
"""Construct a DB-API connection to Google BigQuery.
Args:
client (Optional[google.cloud.bigquery.Client]):
A REST API client used to connect to BigQuery. If not passed, a
client is created using default options inferred from the environment.
bqstorage_client(\
Optional[google.cloud.bigquery_storage_v1.BigQueryReadClient] \
):
A client that uses the faster BigQuery Storage API to fetch rows from
BigQuery. If not passed, it is created using the same credentials
as ``client`` (provided that BigQuery Storage dependencies are installed).
prefer_bqstorage_client (Optional[bool]):
Prefer the BigQuery Storage client over the REST client. If Storage
client isn't available, fall back to the REST client. Defaults to
``True``.
Returns:
google.cloud.bigquery.dbapi.Connection: A new DB-API connection to BigQuery.
"""
return Connection(client, bqstorage_client, prefer_bqstorage_client)
|