mygpo/core/models.py

   1 """ This module contains abstract models that are used in multiple apps """
   2
   3 from __future__ import absolute_import, unicode_literals
   4
   5 import json
   6
   7 from uuidfield import UUIDField
   8
   9 from django.db import models, connection
  10
  11
  12 class UUIDModel(models.Model):
  13     """ Models that have an UUID as primary key """
  14
  15     id = UUIDField(primary_key=True)
  16
  17     class Meta:
  18         abstract = True
  19
  20     def get_id(self):
  21         """ String representation of the ID """
  22         return self.id.hex
  23
  24
  25 class TwitterModel(models.Model):
  26     """ A model that has a twitter handle """
  27
  28     twitter = models.CharField(max_length=15, null=True, blank=False)
  29
  30     class Meta:
  31         abstract = True
  32
  33
  34 class GenericManager(models.Manager):
  35     """ Generic manager methods """
  36
  37     def count_fast(self):
  38         """ Fast approximate count of all model instances
  39
  40         PostgreSQL is slow when counting records without an index. This is a
  41         workaround which only gives approximate results. see:
  42         http://wiki.postgresql.org/wiki/Slow_Counting """
  43         cursor = connection.cursor()
  44         cursor.execute("select reltuples from pg_class where relname='%s';" %
  45                        self.model._meta.db_table)
  46         row = cursor.fetchone()
  47         return int(row[0])
  48
  49
  50 class UpdateInfoModel(models.Model):
  51     """ Model that keeps track of when it was created and updated """
  52     created = models.DateTimeField(auto_now_add=True)
  53     modified = models.DateTimeField(auto_now=True)
  54
  55     class Meta:
  56         abstract = True
  57
  58
  59 class DeleteableModel(models.Model):
  60     """ A model that can be marked as deleted """
  61
  62     # indicates that the object has been deleted
  63     deleted = models.BooleanField(default=False)
  64
  65     class Meta:
  66         abstract = True
  67
  68
  69 class OrderedModel(models.Model):
  70     """ A model that can be ordered
  71
  72     The implementing Model must make sure that 'order' is sufficiently unique
  73     """
  74
  75     order = models.PositiveSmallIntegerField()
  76
  77     class Meta:
  78         abstract = True
  79         ordering = ['order']