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)
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):
response = api.partition_read(
request=request,
metadata=metadata,
retry=retry,
timeout=timeout,
)
return [partition.partition_token for partition in response.partitions]
def _partition_read_helper(
self, multi_use, w_txn, size=None, max_partitions=None, index=None
):
from google.cloud.spanner_v1.keyset import KeySet
from google.cloud.spanner_v1 import Partition
from google.cloud.spanner_v1 import PartitionOptions
from google.cloud.spanner_v1 import PartitionReadRequest
from google.cloud.spanner_v1 import PartitionResponse
from google.cloud.spanner_v1 import Transaction
from google.cloud.spanner_v1 import TransactionSelector
keyset = KeySet(all_=True)
new_txn_id = b"ABECAB91"
token_1 = b"FACE0FFF"
token_2 = b"BADE8CAF"
response = PartitionResponse(
partitions=[
Partition(partition_token=token_1),
Partition(partition_token=token_2),
],
transaction=Transaction(id=new_txn_id),
)
database = _Database()
api = database.spanner_api = self._make_spanner_api()
api.partition_read.return_value = response
session = _Session(database)
derived = self._makeDerived(session)
derived._multi_use = multi_use
if w_txn:
derived._transaction_id = TXN_ID
tokens = list(
derived.partition_read(
TABLE_NAME,
COLUMNS,
keyset,
index=index,
partition_size_bytes=size,
max_partitions=max_partitions,
)
)
self.assertEqual(tokens, [token_1, token_2])
expected_txn_selector = TransactionSelector(id=TXN_ID)
expected_partition_options = PartitionOptions(
partition_size_bytes=size, max_partitions=max_partitions
)
expected_request = PartitionReadRequest(
session=self.SESSION_NAME,
table=TABLE_NAME,
columns=COLUMNS,
key_set=keyset._to_pb(),
transaction=expected_txn_selector,
index=index,
partition_options=expected_partition_options,
)
api.partition_read.assert_called_once_with(
request=expected_request,
metadata=[("google-cloud-resource-prefix", database.name)],
)
self.assertSpanAttributes(
"CloudSpanner.PartitionReadOnlyTransaction",
status=StatusCanonicalCode.OK,
attributes=dict(
BASE_ATTRIBUTES, table_id=TABLE_NAME, columns=tuple(COLUMNS)
),
)