def __enter__(self):
"""Begin ``with`` block."""
session = self._session = self._database._pool.get()
return Snapshot(
session,
read_timestamp=self._read_timestamp,
min_read_timestamp=self._min_read_timestamp,
max_staleness=self._max_staleness,
exact_staleness=self._exact_staleness,
)
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.snapshot.Snapshot` ctor.
:rtype: :class:`~google.cloud.spanner.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 snapshot(self,
read_timestamp=None,
min_read_timestamp=None,
max_staleness=None,
exact_staleness=None):
"""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
If no options are passed, reads will use the ``strong`` model, reading
at a timestamp where all previously committed transactions are visible.
: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.
:rtype: :class:`~google.cloud.spanner.snapshot.Snapshot`
:returns: a snapshot bound to this session
:raises: :exc:`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,
read_timestamp=read_timestamp,
min_read_timestamp=min_read_timestamp,
max_staleness=max_staleness,
exact_staleness=exact_staleness)
def __enter__(self):
"""Begin ``with`` block."""
session = self._session = self._database._pool.get()
return Snapshot(session, **self._kw)