Source code for google.cloud.spanner_v1.transaction

# 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()