mygpo/core/models.py

   1 """ This module contains abstract models that are used in multiple apps """
   2
   3
   4 from django.db import models, connection
   5
   6
   7 class UUIDModel(models.Model):
   8     """ Models that have an UUID as primary key """
   9
  10     id = models.UUIDField(primary_key=True)
  11
  12     class Meta:
  13         abstract = True
  14
  15     def get_id(self):
  16         """ String representation of the ID """
  17         return self.id
  18
  19
  20 class TwitterModel(models.Model):
  21     """ A model that has a twitter handle """
  22
  23     twitter = models.CharField(max_length=15, null=True, blank=True)
  24
  25     class Meta:
  26         abstract = True
  27
  28
  29 class GenericManager(models.Manager):
  30     """ Generic manager methods """
  31
  32     def count_fast(self):
  33         """ Fast approximate count of all model instances
  34
  35         PostgreSQL is slow when counting records without an index. This is a
  36         workaround which only gives approximate results. see:
  37         http://wiki.postgresql.org/wiki/Slow_Counting """
  38         cursor = connection.cursor()
  39         cursor.execute(
  40             "select reltuples from pg_class where relname='%s';"
  41             % self.model._meta.db_table
  42         )
  43         row = cursor.fetchone()
  44         return int(row[0])
  45
  46
  47 class UpdateInfoModel(models.Model):
  48     """ Model that keeps track of when it was created and updated """
  49
  50     created = models.DateTimeField(auto_now_add=True)
  51     modified = models.DateTimeField(auto_now=True)
  52
  53     class Meta:
  54         abstract = True
  55
  56
  57 class DeleteableModel(models.Model):
  58     """ A model that can be marked as deleted """
  59
  60     # indicates that the object has been deleted
  61     deleted = models.BooleanField(default=False)
  62
  63     class Meta:
  64         abstract = True
  65
  66
  67 class OrderedModel(models.Model):
  68     """ A model that can be ordered
  69
  70     The implementing Model must make sure that 'order' is sufficiently unique
  71     """
  72
  73     order = models.PositiveSmallIntegerField()
  74
  75     class Meta:
  76         abstract = True
  77         ordering = ['order']
  78
  79
  80 class OptionallyOrderedModel(models.Model):
  81     """ A model that can be ordered, w/ unknown order of individual objects
  82
  83     The implementing Model must make sure that 'order' is sufficiently unique
  84     """
  85
  86     order = models.BigIntegerField(null=True, default=None)
  87
  88     class Meta:
  89         abstract = True
  90         ordering = ['order']