src/catalogue/migrations/0003_populate_ancestors.py

   1 # -*- coding: utf-8 -*-
   2 from __future__ import unicode_literals
   3
   4 from django.db import migrations
   5
   6
   7 def populate_ancestors(apps, schema_editor):
   8     """Fixes the ancestry cache."""
   9     # TODO: table names
  10     from django.db import connection, transaction
  11     if connection.vendor == 'postgres':
  12         cursor = connection.cursor()
  13         cursor.execute("""
  14             WITH RECURSIVE ancestry AS (
  15                 SELECT book.id, book.parent_id
  16                 FROM catalogue_book AS book
  17                 WHERE book.parent_id IS NOT NULL
  18                 UNION
  19                 SELECT ancestor.id, book.parent_id
  20                 FROM ancestry AS ancestor, catalogue_book AS book
  21                 WHERE ancestor.parent_id = book.id
  22                     AND book.parent_id IS NOT NULL
  23                 )
  24             INSERT INTO catalogue_book_ancestor
  25                 (from_book_id, to_book_id)
  26                 SELECT id, parent_id
  27                 FROM ancestry
  28                 ORDER BY id;
  29             """)
  30     else:
  31         Book = apps.get_model("catalogue", "Book")
  32         for book in Book.objects.exclude(parent=None):
  33             parent = book.parent
  34             while parent is not None:
  35                 book.ancestor.add(parent)
  36                 parent = parent.parent
  37
  38
  39 def remove_book_tags(apps, schema_editor):
  40     Tag = apps.get_model("catalogue", "Tag")
  41     Book = apps.get_model("catalogue", "Book")
  42     Tag.objects.filter(category='book').delete()
  43
  44
  45 class Migration(migrations.Migration):
  46
  47     dependencies = [
  48         ('catalogue', '0002_book_ancestor'),
  49     ]
  50
  51     operations = [
  52         migrations.RunPython(populate_ancestors),
  53         migrations.RunPython(remove_book_tags),
  54     ]