def sample_row_keys(self):
"""Read a sample of row keys in the table.
The returned row keys will delimit contiguous sections of the table of
approximately equal size, which can be used to break up the data for
distributed tasks like mapreduces.
The elements in the iterator are a SampleRowKeys response and they have
the properties ``offset_bytes`` and ``row_key``. They occur in sorted
order. The table might have contents before the first row key in the
list and after the last one, but a key containing the empty string
indicates "end of table" and will be the last response given, if
present.
.. note::
Row keys in this list may not have ever been written to or read
from, and users should therefore not make any assumptions about the
row key structure that are specific to their use case.
The ``offset_bytes`` field on a response indicates the approximate
total storage space used by all rows in the table which precede
``row_key``. Buffering the contents of all rows between two subsequent
samples would require space roughly equal to the difference in their
``offset_bytes`` fields.
:rtype: :class:`grpc.framework.alpha._reexport._CancellableIterator`
:returns: A cancel-able iterator. Can be consumed by calling ``next()``
or by casting to a :class:`list` and can be cancelled by
calling ``cancel()``.
"""
request_pb = data_messages_v2_pb2.SampleRowKeysRequest(
table_name=self.name)
client = self._instance._client
response_iterator = client._data_stub.SampleRowKeys(
request_pb, client.timeout_seconds)
return response_iterator
def _SampleRowKeysRequestPB(*args, **kw):
from gcloud.bigtable._generated import (bigtable_pb2 as messages_v2_pb2)
return messages_v2_pb2.SampleRowKeysRequest(*args, **kw)