A simple test for Google's Cloud Datastore to see if property name length affects entity size on disk.

app.yaml

application: jeremydw-hrd
version: property-name-length-test
api_version: 1
runtime: python27
threadsafe: true

handlers:

- url: /.*
  script: main.application

main.py

import logging
import time
import webapp2
from google.appengine.ext import ndb
from google.appengine.ext.db import stats


class PersistentClass1(ndb.Model):
  super_very_long_property_name = ndb.StringProperty()


class PersistentClass2(ndb.Model):
  l = ndb.StringProperty()


class TestHandler(webapp2.RequestHandler):

  def get(self):
    self.response.headers['Content-Type'] = 'text/plain'

    # NOTE: You'll have to visit the development server admin console and press the "Generate stats"
    # button from the "Datastore Stats" page in order for these statistics to be generated.
    vals = stats.KindPropertyNameStat.all()
    for val in vals:
      self.response.out.write('name: {}, bytes: {}\n'.format(val.key().name(), val.bytes))

    bigger = stats.KindPropertyNameStat.get_by_key_name('super_very_long_property_name_PersistentClass1')
    smaller = stats.KindPropertyNameStat.get_by_key_name('l_PersistentClass2')
    self.response.out.write('difference: {} bytes'.format(bigger.bytes - smaller.bytes))


class InitHandler(webapp2.RequestHandler):
  """Creates 2000 entities each for long and short property names."""

  def get(self):
    self.response.headers['Content-Type'] = 'text/plain'

    start = time.time()
    entities = []
    for i in xrange(1, 2000):
      key_id = 'persistent-class-1-{}'.format(i)
      entity = PersistentClass1(id=key_id, super_very_long_property_name='foobar')
      entities.append(entity)
    ndb.put_multi(entities)
    bigger_time = time.time() - start
    self.response.out.write('Took {} seconds for long property names.\n'.format(bigger_time))

    start = time.time()
    entities = []
    for i in xrange(1, 2000):
      key_id = 'persistent-class-2-{}'.format(i)
      entity = PersistentClass2(id=key_id, l='foobar')
      entities.append(entity)
    ndb.put_multi(entities)
    shorter_time = time.time() - start
    self.response.out.write('Took {} seconds for short property names.\n'.format(shorter_time))

    self.response.out.write('difference: {}'.format(bigger_time - shorter_time))


application = webapp2.WSGIApplication([
    ('/init', InitHandler),
    ('/test', TestHandler),
])

Results of running this using dev_appserver:

/init
Took 4.65448188782 seconds for long property names.
Took 4.62077403069 seconds for short property names.
difference: 0.033707857132

/test
name: l_PersistentClass2, bytes: 1507635
name: super_very_long_property_name_PersistentClass1, bytes: 1787607
difference: 279972 bytes