def check_estimated_size_bytes(self, entity_bytes, timestamp, namespace=None):
"""A helper method to test get_estimated_size_bytes"""
timestamp_req = helper.make_request(
self._PROJECT, namespace, helper.make_latest_timestamp_query(namespace))
timestamp_resp = self.make_stats_response(
{'timestamp': datastore_helper.from_timestamp(timestamp)})
kind_stat_req = helper.make_request(
self._PROJECT, namespace, helper.make_kind_stats_query(
namespace, self._query.kind[0].name,
datastore_helper.micros_from_timestamp(timestamp)))
kind_stat_resp = self.make_stats_response(
{'entity_bytes': entity_bytes})
def fake_run_query(req):
if req == timestamp_req:
return timestamp_resp
elif req == kind_stat_req:
return kind_stat_resp
else:
print kind_stat_req
raise ValueError("Unknown req: %s" % req)
self._mock_datastore.run_query.side_effect = fake_run_query
self.assertEqual(entity_bytes, ReadFromDatastore.get_estimated_size_bytes(
self._PROJECT, namespace, self._query, self._mock_datastore))
self.assertEqual(self._mock_datastore.run_query.call_args_list,
[call(timestamp_req), call(kind_stat_req)])
def get_estimated_size_bytes(project, namespace, query, datastore):
"""Get the estimated size of the data returned by the given query.
Cloud Datastore provides no way to get a good estimate of how large the
result of a query is going to be. Hence we use the __Stat_Kind__ system
table to get size of the entire kind as an approximate estimate, assuming
exactly 1 kind is specified in the query.
See https://cloud.google.com/datastore/docs/concepts/stats.
"""
kind = query.kind[0].name
latest_timestamp = ReadFromDatastore.query_latest_statistics_timestamp(
project, namespace, datastore)
logging.info('Latest stats timestamp for kind %s is %s', kind,
latest_timestamp)
kind_stats_query = (helper.make_kind_stats_query(
namespace, kind, latest_timestamp))
req = helper.make_request(project, namespace, kind_stats_query)
resp = datastore.run_query(req)
if len(resp.batch.entity_results) == 0:
raise RuntimeError("Datastore statistics for kind %s unavailable" %
kind)
entity = resp.batch.entity_results[0].entity
return datastore_helper.get_value(entity.properties['entity_bytes'])
def query_latest_statistics_timestamp(project, namespace, datastore):
"""Fetches the latest timestamp of statistics from Cloud Datastore.
Cloud Datastore system tables with statistics are periodically updated.
This method fethes the latest timestamp (in microseconds) of statistics
update using the `__Stat_Total__` table.
"""
query = helper.make_latest_timestamp_query(namespace)
req = helper.make_request(project, namespace, query)
resp = datastore.run_query(req)
if len(resp.batch.entity_results) == 0:
raise RuntimeError("Datastore total statistics unavailable.")
entity = resp.batch.entity_results[0].entity
return datastore_helper.micros_from_timestamp(
entity.properties['timestamp'].timestamp_value)