As of January 1, 2020 this library no longer supports Python 2 on the latest released version.
Library versions released prior to that date will continue to be available. For more information please
visit Python 2 support on Google Cloud.
Source code for google.cloud.spanner_v1.snapshot
# 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.
"""Model a set of read-only queries to a database as a snapshot."""
import functools
import threading
from google.protobuf.struct_pb2 import Struct
from google.cloud.spanner_v1 import ExecuteSqlRequest
from google.cloud.spanner_v1 import ReadRequest
from google.cloud.spanner_v1 import TransactionOptions
from google.cloud.spanner_v1 import TransactionSelector
from google.cloud.spanner_v1 import PartitionOptions
from google.cloud.spanner_v1 import PartitionQueryRequest
from google.cloud.spanner_v1 import PartitionReadRequest
from google.api_core.exceptions import InternalServerError
from google.api_core.exceptions import ServiceUnavailable
from google.api_core.exceptions import InvalidArgument
from google.api_core import gapic_v1
from google.cloud.spanner_v1._helpers import (
_make_value_pb,
_merge_query_options,
_metadata_with_prefix,
_metadata_with_leader_aware_routing,
_retry,
_check_rst_stream_error,
_SessionWrapper,
)
from google.cloud.spanner_v1._opentelemetry_tracing import trace_call
from google.cloud.spanner_v1.streamed import StreamedResultSet
from google.cloud.spanner_v1 import RequestOptions
_STREAM_RESUMPTION_INTERNAL_ERROR_MESSAGES = (
"RST_STREAM",
"Received unexpected EOS on DATA frame from server",
)
def _restart_on_unavailable(
method,
request,
trace_name=None,
session=None,
attributes=None,
transaction=None,
transaction_selector=None,
):
"""Restart iteration after :exc:`.ServiceUnavailable`.
:type method: callable
:param method: function returning iterator
:type request: proto
:param request: request proto to call the method with
:type transaction: :class:`google.cloud.spanner_v1.snapshot._SnapshotBase`
:param transaction: Snapshot or Transaction class object based on the type of transaction
:type transaction_selector: :class:`transaction_pb2.TransactionSelector`
:param transaction_selector: Transaction selector object to be used in request if transaction is not passed,
if both transaction_selector and transaction are passed, then transaction is given priority.
"""
resume_token = b""
item_buffer = []
if transaction is not None:
transaction_selector = transaction._make_txn_selector()
elif transaction_selector is None:
raise InvalidArgument(
"Either transaction or transaction_selector should be set"
)
request.transaction = transaction_selector
with trace_call(trace_name, session, attributes):
iterator = method(request=request)
while True:
try:
for item in iterator:
item_buffer.append(item)
# Setting the transaction id because the transaction begin was inlined for first rpc.
if (
transaction is not None
and transaction._transaction_id is None
and item.metadata is not None
and item.metadata.transaction is not None
and item.metadata.transaction.id is not None
):
transaction._transaction_id = item.metadata.transaction.id
if item.resume_token:
resume_token = item.resume_token
break
except ServiceUnavailable:
del item_buffer[:]
with trace_call(trace_name, session, attributes):
request.resume_token = resume_token
if transaction is not None:
transaction_selector = transaction._make_txn_selector()
request.transaction = transaction_selector
iterator = method(request=request)
continue
except InternalServerError as exc:
resumable_error = any(
resumable_message in exc.message
for resumable_message in _STREAM_RESUMPTION_INTERNAL_ERROR_MESSAGES
)
if not resumable_error:
raise
del item_buffer[:]
with trace_call(trace_name, session, attributes):
request.resume_token = resume_token
if transaction is not None:
transaction_selector = transaction._make_txn_selector()
request.transaction = transaction_selector
iterator = method(request=request)
continue
if len(item_buffer) == 0:
break
for item in item_buffer:
yield item
del item_buffer[:]
class _SnapshotBase(_SessionWrapper):
"""Base class for Snapshot.
Allows reuse of API request methods with different transaction selector.
:type session: :class:`~google.cloud.spanner_v1.session.Session`
:param session: the session used to perform the commit
"""
_multi_use = False
_read_only: bool = True
_transaction_id = None
_read_request_count = 0
_execute_sql_count = 0
_lock = threading.Lock()
def _make_txn_selector(self):
"""Helper for :meth:`read` / :meth:`execute_sql`.
Subclasses must override, returning an instance of
:class:`transaction_pb2.TransactionSelector`
appropriate for making ``read`` / ``execute_sql`` requests
:raises: NotImplementedError, always
"""
raise NotImplementedError
def read(
self,
table,
columns,
keyset,
index="",
limit=0,
partition=None,
request_options=None,
data_boost_enabled=False,
directed_read_options=None,
*,
retry=gapic_v1.method.DEFAULT,
timeout=gapic_v1.method.DEFAULT,
column_info=None,
):
"""Perform a ``StreamingRead`` API request for rows in a table.
:type table: str
:param table: name of the table from which to fetch data
:type columns: list of str
:param columns: names of columns to be retrieved
:type keyset: :class:`~google.cloud.spanner_v1.keyset.KeySet`
:param keyset: keys / ranges identifying rows to be retrieved
:type index: str
:param index: (Optional) name of index to use, rather than the
table's primary key
:type limit: int
:param limit: (Optional) maximum number of rows to return.
Incompatible with ``partition``.
:type partition: bytes
:param partition: (Optional) one of the partition tokens returned
from :meth:`partition_read`. Incompatible with
``limit``.
:type request_options:
:class:`google.cloud.spanner_v1.types.RequestOptions`
:param request_options:
(Optional) Common options for this request.
If a dict is provided, it must be of the same form as the protobuf
message :class:`~google.cloud.spanner_v1.types.RequestOptions`.
Please note, the `transactionTag` setting will be ignored for
snapshot as it's not supported for read-only transactions.
:type retry: :class:`~google.api_core.retry.Retry`
:param retry: (Optional) The retry settings for this request.
:type timeout: float
:param timeout: (Optional) The timeout for this request.
:type data_boost_enabled:
:param data_boost_enabled:
(Optional) If this is for a partitioned read and this field is
set ``true``, the request will be executed via offline access.
If the field is set to ``true`` but the request does not set
``partition_token``, the API will return an
``INVALID_ARGUMENT`` error.
:type directed_read_options: :class:`~google.cloud.spanner_v1.DirectedReadOptions`
or :class:`dict`
:param directed_read_options: (Optional) Request level option used to set the directed_read_options
for all ReadRequests and ExecuteSqlRequests that indicates which replicas
or regions should be used for non-transactional reads or queries.
:type column_info: dict
:param column_info: (Optional) dict of mapping between column names and additional column information.
An object where column names as keys and custom objects as corresponding
values for deserialization. It's specifically useful for data types like
protobuf where deserialization logic is on user-specific code. When provided,
the custom object enables deserialization of backend-received column data.
If not provided, data remains serialized as bytes for Proto Messages and
integer for Proto Enums.
:rtype: :class:`~google.cloud.spanner_v1.streamed.StreamedResultSet`
:returns: a result set instance which can be used to consume rows.
:raises ValueError:
for reuse of single-use snapshots, or if a transaction ID is
already pending for multiple-use snapshots.
"""
if self._read_request_count > 0:
if not self._multi_use:
raise ValueError("Cannot re-use single-use snapshot.")
if self._transaction_id is None and self._read_only:
raise ValueError("Transaction ID pending.")
database = self._session._database
api = database.spanner_api
metadata = _metadata_with_prefix(database.name)
if not self._read_only and database._route_to_leader_enabled:
metadata.append(
_metadata_with_leader_aware_routing(database._route_to_leader_enabled)
)
if request_options is None:
request_options = RequestOptions()
elif type(request_options) is dict:
request_options = RequestOptions(request_options)
if self._read_only:
# Transaction tags are not supported for read only transactions.
request_options.transaction_tag = None
if (
directed_read_options is None
and database._directed_read_options is not None
):
directed_read_options = database._directed_read_options
elif self.transaction_tag is not None:
request_options.transaction_tag = self.transaction_tag
request = ReadRequest(
session=self._session.name,
table=table,
columns=columns,
key_set=keyset._to_pb(),
index=index,
limit=limit,
partition_token=partition,
request_options=request_options,
data_boost_enabled=data_boost_enabled,
directed_read_options=directed_read_options,
)
restart = functools.partial(
api.streaming_read,
request=request,
metadata=metadata,
retry=retry,
timeout=timeout,
)
trace_attributes = {"table_id": table, "columns": columns}
if self._transaction_id is None:
# lock is added to handle the inline begin for first rpc
with self._lock:
iterator = _restart_on_unavailable(
restart,
request,
"CloudSpanner.ReadOnlyTransaction",
self._session,
trace_attributes,
transaction=self,
)
self._read_request_count += 1
if self._multi_use:
return StreamedResultSet(
iterator, source=self, column_info=column_info
)
else:
return StreamedResultSet(iterator, column_info=column_info)
else:
iterator = _restart_on_unavailable(
restart,
request,
"CloudSpanner.ReadOnlyTransaction",
self._session,
trace_attributes,
transaction=self,
)
self._read_request_count += 1
if self._multi_use:
return StreamedResultSet(iterator, source=self, column_info=column_info)
else:
return StreamedResultSet(iterator, column_info=column_info)
def execute_sql(
self,
sql,
params=None,
param_types=None,
query_mode=None,
query_options=None,
request_options=None,
partition=None,
retry=gapic_v1.method.DEFAULT,
timeout=gapic_v1.method.DEFAULT,
data_boost_enabled=False,
directed_read_options=None,
column_info=None,
):
"""Perform an ``ExecuteStreamingSql`` API request.
:type sql: str
:param sql: SQL query statement
:type params: dict, {str -> column value}
:param params: values for parameter replacement. Keys must match
the names used in ``sql``.
: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.types.ExecuteSqlRequest.QueryMode`
:param query_mode: Mode governing return of results / query plan.
See:
`QueryMode <https://cloud.google.com/spanner/reference/rpc/google.spanner.v1#google.spanner.v1.ExecuteSqlRequest.QueryMode>`_.
:type query_options:
:class:`~google.cloud.spanner_v1.types.ExecuteSqlRequest.QueryOptions`
or :class:`dict`
:param query_options:
(Optional) Query optimizer configuration to use for the given query.
If a dict is provided, it must be of the same form as the protobuf
message :class:`~google.cloud.spanner_v1.types.QueryOptions`
:type request_options:
:class:`google.cloud.spanner_v1.types.RequestOptions`
:param request_options:
(Optional) Common options for this request.
If a dict is provided, it must be of the same form as the protobuf
message :class:`~google.cloud.spanner_v1.types.RequestOptions`.
:type partition: bytes
:param partition: (Optional) one of the partition tokens returned
from :meth:`partition_query`.
:rtype: :class:`~google.cloud.spanner_v1.streamed.StreamedResultSet`
:returns: a result set instance which can be used to consume rows.
:type retry: :class:`~google.api_core.retry.Retry`
:param retry: (Optional) The retry settings for this request.
:type timeout: float
:param timeout: (Optional) The timeout for this request.
:type data_boost_enabled:
:param data_boost_enabled:
(Optional) If this is for a partitioned query and this field is
set ``true``, the request will be executed via offline access.
If the field is set to ``true`` but the request does not set
``partition_token``, the API will return an
``INVALID_ARGUMENT`` error.
:type directed_read_options: :class:`~google.cloud.spanner_v1.DirectedReadOptions`
or :class:`dict`
:param directed_read_options: (Optional) Request level option used to set the directed_read_options
for all ReadRequests and ExecuteSqlRequests that indicates which replicas
or regions should be used for non-transactional reads or queries.
:type column_info: dict
:param column_info: (Optional) dict of mapping between column names and additional column information.
An object where column names as keys and custom objects as corresponding
values for deserialization. It's specifically useful for data types like
protobuf where deserialization logic is on user-specific code. When provided,
the custom object enables deserialization of backend-received column data.
If not provided, data remains serialized as bytes for Proto Messages and
integer for Proto Enums.
:raises ValueError:
for reuse of single-use snapshots, or if a transaction ID is
already pending for multiple-use snapshots.
"""
if self._read_request_count > 0:
if not self._multi_use:
raise ValueError("Cannot re-use single-use snapshot.")
if self._transaction_id is None and self._read_only:
raise ValueError("Transaction ID pending.")
if params is not None:
params_pb = Struct(
fields={key: _make_value_pb(value) for key, value in params.items()}
)
else:
params_pb = {}
database = self._session._database
metadata = _metadata_with_prefix(database.name)
if not self._read_only and database._route_to_leader_enabled:
metadata.append(
_metadata_with_leader_aware_routing(database._route_to_leader_enabled)
)
api = database.spanner_api
# Query-level options have higher precedence than client-level and
# environment-level options
default_query_options = database._instance._client._query_options
query_options = _merge_query_options(default_query_options, query_options)
if request_options is None:
request_options = RequestOptions()
elif type(request_options) is dict:
request_options = RequestOptions(request_options)
if self._read_only:
# Transaction tags are not supported for read only transactions.
request_options.transaction_tag = None
if (
directed_read_options is None
and database._directed_read_options is not None
):
directed_read_options = database._directed_read_options
elif self.transaction_tag is not None:
request_options.transaction_tag = self.transaction_tag
request = ExecuteSqlRequest(
session=self._session.name,
sql=sql,
params=params_pb,
param_types=param_types,
query_mode=query_mode,
partition_token=partition,
seqno=self._execute_sql_count,
query_options=query_options,
request_options=request_options,
data_boost_enabled=data_boost_enabled,
directed_read_options=directed_read_options,
)
restart = functools.partial(
api.execute_streaming_sql,
request=request,
metadata=metadata,
retry=retry,
timeout=timeout,
)
trace_attributes = {"db.statement": sql}
if self._transaction_id is None:
# lock is added to handle the inline begin for first rpc
with self._lock:
return self._get_streamed_result_set(
restart, request, trace_attributes, column_info
)
else:
return self._get_streamed_result_set(
restart, request, trace_attributes, column_info
)
def _get_streamed_result_set(self, restart, request, trace_attributes, column_info):
iterator = _restart_on_unavailable(
restart,
request,
"CloudSpanner.ReadWriteTransaction",
self._session,
trace_attributes,
transaction=self,
)
self._read_request_count += 1
self._execute_sql_count += 1
if self._multi_use:
return StreamedResultSet(iterator, source=self, column_info=column_info)
else:
return StreamedResultSet(iterator, column_info=column_info)
def partition_read(
self,
table,
columns,
keyset,
index="",
partition_size_bytes=None,
max_partitions=None,
*,
retry=gapic_v1.method.DEFAULT,
timeout=gapic_v1.method.DEFAULT,
):
"""Perform a ``PartitionRead`` API request for rows in a table.
:type table: str
:param table: name of the table from which to fetch data
:type columns: list of str
:param columns: names of columns to be retrieved
:type keyset: :class:`~google.cloud.spanner_v1.keyset.KeySet`
:param keyset: keys / ranges identifying rows to be retrieved
:type index: str
:param index: (Optional) name of index to use, rather than the
table's primary key
:type partition_size_bytes: int
:param partition_size_bytes:
(Optional) desired size for each partition generated. The service
uses this as a hint, the actual partition size may differ.
:type max_partitions: int
:param max_partitions:
(Optional) desired maximum number of partitions generated. The
service uses this as a hint, the actual number of partitions may
differ.
:type retry: :class:`~google.api_core.retry.Retry`
:param retry: (Optional) The retry settings for this request.
:type timeout: float
:param timeout: (Optional) The timeout for this request.
:rtype: iterable of bytes
:returns: a sequence of partition tokens
:raises ValueError:
for single-use snapshots, or if a transaction ID is
already associated with the snapshot.
"""
if not self._multi_use:
raise ValueError("Cannot use single-use snapshot.")
if self._transaction_id is None:
raise ValueError("Transaction not started.")
database = self._session._database
api = database.spanner_api
metadata = _metadata_with_prefix(database.name)
if database._route_to_leader_enabled:
metadata.append(
_metadata_with_leader_aware_routing(database._route_to_leader_enabled)
)
transaction = self._make_txn_selector()
partition_options = PartitionOptions(
partition_size_bytes=partition_size_bytes, max_partitions=max_partitions
)
request = PartitionReadRequest(
session=self._session.name,
table=table,
columns=columns,
key_set=keyset._to_pb(),
transaction=transaction,
index=index,
partition_options=partition_options,
)
trace_attributes = {"table_id": table, "columns": columns}
with trace_call(
"CloudSpanner.PartitionReadOnlyTransaction", self._session, trace_attributes
):
method = functools.partial(
api.partition_read,
request=request,
metadata=metadata,
retry=retry,
timeout=timeout,
)
response = _retry(
method,
allowed_exceptions={InternalServerError: _check_rst_stream_error},
)
return [partition.partition_token for partition in response.partitions]
def partition_query(
self,
sql,
params=None,
param_types=None,
partition_size_bytes=None,
max_partitions=None,
*,
retry=gapic_v1.method.DEFAULT,
timeout=gapic_v1.method.DEFAULT,
):
"""Perform a ``PartitionQuery`` API request.
:type sql: str
:param sql: SQL query statement
:type params: dict, {str -> column value}
:param params: values for parameter replacement. Keys must match
the names used in ``sql``.
: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 partition_size_bytes: int
:param partition_size_bytes:
(Optional) desired size for each partition generated. The service
uses this as a hint, the actual partition size may differ.
:type max_partitions: int
:param max_partitions:
(Optional) desired maximum number of partitions generated. The
service uses this as a hint, the actual number of partitions may
differ.
:type retry: :class:`~google.api_core.retry.Retry`
:param retry: (Optional) The retry settings for this request.
:type timeout: float
:param timeout: (Optional) The timeout for this request.
:rtype: iterable of bytes
:returns: a sequence of partition tokens
:raises ValueError:
for single-use snapshots, or if a transaction ID is
already associated with the snapshot.
"""
if not self._multi_use:
raise ValueError("Cannot use single-use snapshot.")
if self._transaction_id is None:
raise ValueError("Transaction not started.")
if params is not None:
params_pb = Struct(
fields={key: _make_value_pb(value) for (key, value) in params.items()}
)
else:
params_pb = Struct()
database = self._session._database
api = database.spanner_api
metadata = _metadata_with_prefix(database.name)
if database._route_to_leader_enabled:
metadata.append(
_metadata_with_leader_aware_routing(database._route_to_leader_enabled)
)
transaction = self._make_txn_selector()
partition_options = PartitionOptions(
partition_size_bytes=partition_size_bytes, max_partitions=max_partitions
)
request = PartitionQueryRequest(
session=self._session.name,
sql=sql,
transaction=transaction,
params=params_pb,
param_types=param_types,
partition_options=partition_options,
)
trace_attributes = {"db.statement": sql}
with trace_call(
"CloudSpanner.PartitionReadWriteTransaction",
self._session,
trace_attributes,
):
method = functools.partial(
api.partition_query,
request=request,
metadata=metadata,
retry=retry,
timeout=timeout,
)
response = _retry(
method,
allowed_exceptions={InternalServerError: _check_rst_stream_error},
)
return [partition.partition_token for partition in response.partitions]
[docs]class Snapshot(_SnapshotBase):
"""Allow a set of reads / SQL statements with shared staleness.
See
https://cloud.google.com/spanner/reference/rpc/google.spanner.v1#google.spanner.v1.TransactionOptions.ReadOnly
If no options are passed, reads will use the ``strong`` model, reading
at a timestamp where all previously committed transactions are visible.
:type session: :class:`~google.cloud.spanner_v1.session.Session`
:param session: The session used to perform the commit.
:type read_timestamp: :class:`datetime.datetime`
:param read_timestamp: Execute all reads at the given timestamp.
:type min_read_timestamp: :class:`datetime.datetime`
:param min_read_timestamp: Execute all reads at a
timestamp >= ``min_read_timestamp``.
:type max_staleness: :class:`datetime.timedelta`
:param max_staleness: Read data at a
timestamp >= NOW - ``max_staleness`` seconds.
:type exact_staleness: :class:`datetime.timedelta`
:param exact_staleness: Execute all reads at a timestamp that is
``exact_staleness`` old.
:type multi_use: :class:`bool`
:param multi_use: If true, multiple :meth:`read` / :meth:`execute_sql`
calls can be performed with the snapshot in the
context of a read-only transaction, used to ensure
isolation / consistency. Incompatible with
``max_staleness`` and ``min_read_timestamp``.
"""
def __init__(
self,
session,
read_timestamp=None,
min_read_timestamp=None,
max_staleness=None,
exact_staleness=None,
multi_use=False,
transaction_id=None,
):
super(Snapshot, self).__init__(session)
opts = [read_timestamp, min_read_timestamp, max_staleness, exact_staleness]
flagged = [opt for opt in opts if opt is not None]
if len(flagged) > 1:
raise ValueError("Supply zero or one options.")
if multi_use:
if min_read_timestamp is not None or max_staleness is not None:
raise ValueError(
"'multi_use' is incompatible with "
"'min_read_timestamp' / 'max_staleness'"
)
self._transaction_read_timestamp = None
self._strong = len(flagged) == 0
self._read_timestamp = read_timestamp
self._min_read_timestamp = min_read_timestamp
self._max_staleness = max_staleness
self._exact_staleness = exact_staleness
self._multi_use = multi_use
self._transaction_id = transaction_id
def _make_txn_selector(self):
"""Helper for :meth:`read`."""
if self._transaction_id is not None:
return TransactionSelector(id=self._transaction_id)
if self._read_timestamp:
key = "read_timestamp"
value = self._read_timestamp
elif self._min_read_timestamp:
key = "min_read_timestamp"
value = self._min_read_timestamp
elif self._max_staleness:
key = "max_staleness"
value = self._max_staleness
elif self._exact_staleness:
key = "exact_staleness"
value = self._exact_staleness
else:
key = "strong"
value = True
options = TransactionOptions(
read_only=TransactionOptions.ReadOnly(
**{key: value, "return_read_timestamp": True}
)
)
if self._multi_use:
return TransactionSelector(begin=options)
else:
return TransactionSelector(single_use=options)
[docs] def begin(self):
"""Begin a read-only 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 not self._multi_use:
raise ValueError("Cannot call 'begin' on single-use snapshots")
if self._transaction_id is not None:
raise ValueError("Read-only transaction already begun")
if self._read_request_count > 0:
raise ValueError("Read-only transaction already pending")
database = self._session._database
api = database.spanner_api
metadata = _metadata_with_prefix(database.name)
if not self._read_only and database._route_to_leader_enabled:
metadata.append(
(_metadata_with_leader_aware_routing(database._route_to_leader_enabled))
)
txn_selector = self._make_txn_selector()
with trace_call("CloudSpanner.BeginTransaction", self._session):
method = functools.partial(
api.begin_transaction,
session=self._session.name,
options=txn_selector.begin,
metadata=metadata,
)
response = _retry(
method,
allowed_exceptions={InternalServerError: _check_rst_stream_error},
)
self._transaction_id = response.id
self._transaction_read_timestamp = response.read_timestamp
return self._transaction_id
