# Copyright 2016 Google LLC All rights reserved.
#
# 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.
"""Spanner read-write transaction support."""
from google.protobuf.struct_pb2 import Struct
from google.cloud._helpers import _pb_timestamp_to_datetime
from google.cloud.spanner_v1._helpers import _make_value_pb
from google.cloud.spanner_v1._helpers import _metadata_with_prefix
from google.cloud.spanner_v1.proto.transaction_pb2 import TransactionSelector
from google.cloud.spanner_v1.proto.transaction_pb2 import TransactionOptions
from google.cloud.spanner_v1.snapshot import _SnapshotBase
from google.cloud.spanner_v1.batch import _BatchBase
[docs]class Transaction(_SnapshotBase, _BatchBase):
"""Implement read-write transaction semantics for a session.
:type session: :class:`~google.cloud.spanner_v1.session.Session`
:param session: the session used to perform the commit
:raises ValueError: if session has an existing transaction
"""
committed = None
"""Timestamp at which the transaction was successfully committed."""
_rolled_back = False
_multi_use = True
_execute_sql_count = 0
def __init__(self, session):
if session._transaction is not None:
raise ValueError("Session has existing transaction.")
super(Transaction, self).__init__(session)
def _check_state(self):
"""Helper for :meth:`commit` et al.
:raises: :exc:`ValueError` if the object's state is invalid for making
API requests.
"""
if self._transaction_id is None:
raise ValueError("Transaction is not begun")
if self.committed is not None:
raise ValueError("Transaction is already committed")
if self._rolled_back:
raise ValueError("Transaction is already rolled back")
def _make_txn_selector(self):
"""Helper for :meth:`read`.
:rtype:
:class:`~.transaction_pb2.TransactionSelector`
:returns: a selector configured for read-write transaction semantics.
"""
self._check_state()
return TransactionSelector(id=self._transaction_id)
[docs] def begin(self):
"""Begin a transaction on the database.
:rtype: bytes
:returns: the ID for the newly-begun transaction.
:raises ValueError:
if the transaction is already begun, committed, or rolled back.
"""
if self._transaction_id is not None:
raise ValueError("Transaction already begun")
if self.committed is not None:
raise ValueError("Transaction already committed")
if self._rolled_back:
raise ValueError("Transaction is already rolled back")
database = self._session._database
api = database.spanner_api
metadata = _metadata_with_prefix(database.name)
txn_options = TransactionOptions(read_write=TransactionOptions.ReadWrite())
response = api.begin_transaction(
self._session.name, txn_options, metadata=metadata
)
self._transaction_id = response.id
return self._transaction_id
[docs] def rollback(self):
"""Roll back a transaction on the database."""
self._check_state()
database = self._session._database
api = database.spanner_api
metadata = _metadata_with_prefix(database.name)
api.rollback(self._session.name, self._transaction_id, metadata=metadata)
self._rolled_back = True
del self._session._transaction
[docs] def commit(self):
"""Commit mutations to the database.
:rtype: datetime
:returns: timestamp of the committed changes.
:raises ValueError: if there are no mutations to commit.
"""
self._check_state()
database = self._session._database
api = database.spanner_api
metadata = _metadata_with_prefix(database.name)
response = api.commit(
self._session.name,
self._mutations,
transaction_id=self._transaction_id,
metadata=metadata,
)
self.committed = _pb_timestamp_to_datetime(response.commit_timestamp)
del self._session._transaction
return self.committed
@staticmethod
def _make_params_pb(params, param_types):
"""Helper for :meth:`execute_update`.
:type params: dict, {str -> column value}
:param params: values for parameter replacement. Keys must match
the names used in ``dml``.
:type param_types: dict[str -> Union[dict, .types.Type]]
:param param_types:
(Optional) maps explicit types for one or more param values;
required if parameters are passed.
:rtype: Union[None, :class:`Struct`]
:returns: a struct message for the passed params, or None
:raises ValueError:
If ``param_types`` is None but ``params`` is not None.
:raises ValueError:
If ``params`` is None but ``param_types`` is not None.
"""
if params is not None:
if param_types is None:
raise ValueError("Specify 'param_types' when passing 'params'.")
return Struct(
fields={key: _make_value_pb(value) for key, value in params.items()}
)
else:
if param_types is not None:
raise ValueError("Specify 'params' when passing 'param_types'.")
return None
[docs] def execute_update(self, dml, params=None, param_types=None, query_mode=None):
"""Perform an ``ExecuteSql`` API request with DML.
:type dml: str
:param dml: SQL DML statement
:type params: dict, {str -> column value}
:param params: values for parameter replacement. Keys must match
the names used in ``dml``.
:type param_types: dict[str -> Union[dict, .types.Type]]
:param param_types:
(Optional) maps explicit types for one or more param values;
required if parameters are passed.
:type query_mode:
:class:`google.cloud.spanner_v1.proto.ExecuteSqlRequest.QueryMode`
:param query_mode: Mode governing return of results / query plan. See
https://cloud.google.com/spanner/reference/rpc/google.spanner.v1#google.spanner.v1.ExecuteSqlRequest.QueryMode1
:rtype: int
:returns: Count of rows affected by the DML statement.
"""
params_pb = self._make_params_pb(params, param_types)
database = self._session._database
metadata = _metadata_with_prefix(database.name)
transaction = self._make_txn_selector()
api = database.spanner_api
response = api.execute_sql(
self._session.name,
dml,
transaction=transaction,
params=params_pb,
param_types=param_types,
query_mode=query_mode,
seqno=self._execute_sql_count,
metadata=metadata,
)
self._execute_sql_count += 1
return response.stats.row_count_exact
[docs] def batch_update(self, statements):
"""Perform a batch of DML statements via an ``ExecuteBatchDml`` request.
:type statements:
Sequence[Union[ str, Tuple[str, Dict[str, Any], Dict[str, Union[dict, .types.Type]]]]]
:param statements:
List of DML statements, with optional params / param types.
If passed, 'params' is a dict mapping names to the values
for parameter replacement. Keys must match the names used in the
corresponding DML statement. If 'params' is passed, 'param_types'
must also be passed, as a dict mapping names to the type of
value passed in 'params'.
:rtype:
Tuple(status, Sequence[int])
:returns:
Status code, plus counts of rows affected by each completed DML
statement. Note that if the staus code is not ``OK``, the
statement triggering the error will not have an entry in the
list, nor will any statements following that one.
"""
parsed = []
for statement in statements:
if isinstance(statement, str):
parsed.append({"sql": statement})
else:
dml, params, param_types = statement
params_pb = self._make_params_pb(params, param_types)
parsed.append(
{"sql": dml, "params": params_pb, "param_types": param_types}
)
database = self._session._database
metadata = _metadata_with_prefix(database.name)
transaction = self._make_txn_selector()
api = database.spanner_api
response = api.execute_batch_dml(
session=self._session.name,
transaction=transaction,
statements=parsed,
seqno=self._execute_sql_count,
metadata=metadata,
)
self._execute_sql_count += 1
row_counts = [
result_set.stats.row_count_exact for result_set in response.result_sets
]
return response.status, row_counts
def __enter__(self):
"""Begin ``with`` block."""
self.begin()
return self
def __exit__(self, exc_type, exc_val, exc_tb):
"""End ``with`` block."""
if exc_type is None:
self.commit()
else:
self.rollback()