'Do a mix of database operations.'

def _DoMix(self, subjects):

    self.test_name = 'mix'
    for _ in xrange(0, (len(subjects) / 2000)):
        op = self.rand.randint(0, 3)
        if (op == 0):
            self._ReadRandom(subjects, 14, False)
        elif (op == 1):
            self._GrowRandomly(subjects, 5, 20, False)
        elif (op == 2):
            self._UpdateRandom(subjects, 10, False)
        elif (op == 3):
            self._DeleteRandom(subjects, 4, False)
