mediagoblin/db/sql/util.py

   1 # GNU MediaGoblin -- federated, autonomous media hosting
   2 # Copyright (C) 2011 MediaGoblin contributors.  See AUTHORS.
   3 #
   4 # This program is free software: you can redistribute it and/or modify
   5 # it under the terms of the GNU Affero General Public License as published by
   6 # the Free Software Foundation, either version 3 of the License, or
   7 # (at your option) any later version.
   8 #
   9 # This program is distributed in the hope that it will be useful,
  10 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 # GNU Affero General Public License for more details.
  13 #
  14 # You should have received a copy of the GNU Affero General Public License
  15 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
  16
  17
  18 class MigrationManager(object):
  19     """
  20     Migration handling tool.
  21
  22     Takes information about a database, lets you update the database
  23     to the latest migrations, etc.
  24     """
  25
  26     def __init__(self, name, models, migration_registry, database):
  27         """
  28         Args:
  29          - name: identifier of this section of the database
  30          - database: database we're going to migrate
  31          - migration_registry: where we should find all migrations to
  32            run
  33         """
  34         self.name = name
  35         self.models = models
  36         self.database = database
  37         self.migration_registry = migration_registry
  38         self._sorted_migrations = None
  39
  40         # For convenience
  41         from mediagoblin.db.sql.models import MigrationData
  42
  43         self.migration_model = MigrationData
  44         self.migration_table = MigrationData.__table__
  45
  46     @property
  47     def sorted_migrations(self):
  48         """
  49         Sort migrations if necessary and store in self._sorted_migrations
  50         """
  51         if not self._sorted_migrations:
  52             self._sorted_migrations = sorted(
  53                 self.migration_registry.items(),
  54                 # sort on the key... the migration number
  55                 key=lambda migration_tuple: migration_tuple[0])
  56
  57         return self._sorted_migrations
  58
  59     def latest_migration(self):
  60         """
  61         Return a migration number for the latest migration, or 0 if
  62         there are no migrations.
  63         """
  64         if self.sorted_migrations:
  65             return self.sorted_migrations[-1][0]
  66         else:
  67             # If no migrations have been set, we start at 0.
  68             return 0
  69
  70     def database_current_migration(self):
  71         """
  72         Return the current migration in the database.
  73         """
  74         # TODO
  75
  76     def set_current_migration(self, migration_number):
  77         """
  78         Set the migration in the database to migration_number
  79         """
  80         # TODO
  81         pass
  82
  83     def migrations_to_run(self):
  84         """
  85         Get a list of migrations to run still, if any.
  86
  87         Note that calling this will set your migration version to the
  88         latest version if it isn't installed to anything yet!
  89         """
  90         ## TODO
  91         # self._ensure_current_migration_record()
  92         #
  93         # db_current_migration = self.database_current_migration()
  94         #
  95         # return [
  96         #     (migration_number, migration_func)
  97         #     for migration_number, migration_func in self.sorted_migrations
  98         #     if migration_number > db_current_migration]
  99         pass
 100
 101     def init_or_migrate(self):
 102         # Find out what migration number, if any, this database data is at,
 103         # and what the latest is.
 104
 105         # Is this our first time?  Is there even a table entry for
 106         # this identifier?
 107         #
 108         # If so:
 109         #  - create all tables
 110         #  - create record in migrations registry
 111         #  - print / inform the user
 112         #  - return 'inited'
 113
 114         # Run migrations, if appropriate.
 115
 116         # If ran migrations, return 'migrated'.  Otherwise, return None.
 117         pass
 118
 119
 120 class RegisterMigration(object):
 121     """
 122     Tool for registering migrations
 123
 124     Call like:
 125
 126     @RegisterMigration(33)
 127     def update_dwarves(database):
 128         [...]
 129
 130     This will register your migration with the default migration
 131     registry.  Alternately, to specify a very specific
 132     migration_registry, you can pass in that as the second argument.
 133
 134     Note, the number of your migration should NEVER be 0 or less than
 135     0.  0 is the default "no migrations" state!
 136     """
 137     def __init__(self, migration_number, migration_registry):
 138         assert migration_number > 0, "Migration number must be > 0!"
 139         assert migration_number not in migration_registry, \
 140             "Duplicate migration numbers detected!  That's not allowed!"
 141
 142         self.migration_number = migration_number
 143         self.migration_registry = migration_registry
 144
 145     def __call__(self, migration):
 146         self.migration_registry[self.migration_number] = migration
 147         return migration
 148
 149
 150 def assure_migrations_table_setup(db):
 151     """
 152     Make sure the migrations table is set up in the database.
 153     """
 154     from mediagoblin.db.sql.models import MigrationData
 155
 156     if not MigrationData.__table__.exists(db):
 157         MigrationData.metadata.create_all(
 158             db, tables=[MigrationData.__table__])