def snapshot_checkout(self):
"""Get a Cloud Spanner snapshot.
Initiate a new multi-use snapshot, if there is no snapshot in
this connection yet. Return the existing one otherwise.
:rtype: :class:`google.cloud.spanner_v1.snapshot.Snapshot`
:returns: A Cloud Spanner snapshot object, ready to use.
"""
if self.read_only and not self.autocommit:
if not self._snapshot:
self._snapshot = Snapshot(self._session_checkout(),
multi_use=True,
**self.staleness)
self._snapshot.begin()
return self._snapshot
def snapshot(self, **kw):
"""Create a snapshot to perform a set of reads with shared staleness.
See
https://cloud.google.com/spanner/reference/rpc/google.spanner.v1#google.spanner.v1.TransactionOptions.ReadOnly
:type kw: dict
:param kw: Passed through to
:class:`~google.cloud.spanner_v1.snapshot.Snapshot` ctor.
:rtype: :class:`~google.cloud.spanner_v1.snapshot.Snapshot`
:returns: a snapshot bound to this session
:raises ValueError: if the session has not yet been created.
"""
if self._session_id is None:
raise ValueError("Session has not been created.")
return Snapshot(self, **kw)
def __enter__(self):
"""Begin ``with`` block."""
session = self._session = self._database._pool.get()
return Snapshot(session, **self._kw)
