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 import logging
  12 logger = logging.getLogger(__name__)
  13
  14
  15 class UUIDModel(models.Model):
  16     """ Models that have an UUID as primary key """
  17
  18     id = UUIDField(primary_key=True)
  19
  20     class Meta:
  21         abstract = True
  22
  23     def get_id(self):
  24         """ String representation of the ID """
  25         return self.id.hex
  26
  27
  28 class TwitterModel(models.Model):
  29     """ A model that has a twitter handle """
  30
  31     twitter = models.CharField(max_length=15, null=True, blank=False)
  32
  33     class Meta:
  34         abstract = True
  35
  36
  37 class SettingsModel(models.Model):
  38     """ A model that can store arbitrary settings as JSON """
  39
  40     settings = models.TextField(null=False, default='{}')
  41
  42     class Meta:
  43         abstract = True
  44
  45     def get_wksetting(self, setting):
  46         """ returns the value of a well-known setting """
  47         try:
  48             settings = json.loads(self.settings)
  49         except ValueError as ex:
  50             logger.warn('Decoding settings failed: {msg}'.format(msg=str(ex)))
  51             return None
  52
  53         return settings.get(setting.name, setting.default)
  54
  55     def set_wksetting(self, setting, value):
  56         try:
  57             settings = json.loads(self.settings)
  58         except ValueError as ex:
  59             logger.warn('Decoding settings failed: {msg}'.format(msg=str(ex)))
  60             settings = {}
  61         settings[setting.name] = value
  62         self.settings = json.dumps(settings)
  63
  64     def get_setting(self, name, default):
  65         settings = json.loads(self.settings)
  66         return settings.get(name, default)
  67
  68     def set_setting(self, name, value):
  69         settings = json.loads(self.settings)
  70         settings[name] = value
  71         self.settings = json.dumps(settings)
  72
  73
  74 class GenericManager(models.Manager):
  75     """ Generic manager methods """
  76
  77     def count_fast(self):
  78         """ Fast approximate count of all model instances
  79
  80         PostgreSQL is slow when counting records without an index. This is a
  81         workaround which only gives approximate results. see:
  82         http://wiki.postgresql.org/wiki/Slow_Counting """
  83         cursor = connection.cursor()
  84         cursor.execute("select reltuples from pg_class where relname='%s';" %
  85                        self.model._meta.db_table)
  86         row = cursor.fetchone()
  87         return int(row[0])
  88
  89
  90 class UpdateInfoModel(models.Model):
  91     """ Model that keeps track of when it was created and updated """
  92     created = models.DateTimeField(auto_now_add=True)
  93     modified = models.DateTimeField(auto_now=True)
  94
  95     class Meta:
  96         abstract = True
  97
  98
  99 class DeleteableModel(models.Model):
 100     """ A model that can be marked as deleted """
 101
 102     # indicates that the object has been deleted
 103     deleted = models.BooleanField(default=False)
 104
 105     class Meta:
 106         abstract = True
 107
 108
 109 class OrderedModel(models.Model):
 110     """ A model that can be ordered
 111
 112     The implementing Model must make sure that 'order' is sufficiently unique
 113     """
 114
 115     order = models.PositiveSmallIntegerField()
 116
 117     class Meta:
 118         abstract = True
 119         ordering = ['order']