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- from django.apps.registry import Apps
- from django.db import models
- from django.db.utils import DatabaseError
- from django.utils.timezone import now
-
- from .exceptions import MigrationSchemaMissing
-
-
- class MigrationRecorder:
- """
- Deal with storing migration records in the database.
-
- Because this table is actually itself used for dealing with model
- creation, it's the one thing we can't do normally via migrations.
- We manually handle table creation/schema updating (using schema backend)
- and then have a floating model to do queries with.
-
- If a migration is unapplied its row is removed from the table. Having
- a row in the table always means a migration is applied.
- """
-
- class Migration(models.Model):
- app = models.CharField(max_length=255)
- name = models.CharField(max_length=255)
- applied = models.DateTimeField(default=now)
-
- class Meta:
- apps = Apps()
- app_label = "migrations"
- db_table = "django_migrations"
-
- def __str__(self):
- return "Migration %s for %s" % (self.name, self.app)
-
- def __init__(self, connection):
- self.connection = connection
-
- @property
- def migration_qs(self):
- return self.Migration.objects.using(self.connection.alias)
-
- def has_table(self):
- """Return True if the django_migrations table exists."""
- return self.Migration._meta.db_table in self.connection.introspection.table_names(self.connection.cursor())
-
- def ensure_schema(self):
- """Ensure the table exists and has the correct schema."""
- # If the table's there, that's fine - we've never changed its schema
- # in the codebase.
- if self.has_table():
- return
- # Make the table
- try:
- with self.connection.schema_editor() as editor:
- editor.create_model(self.Migration)
- except DatabaseError as exc:
- raise MigrationSchemaMissing("Unable to create the django_migrations table (%s)" % exc)
-
- def applied_migrations(self):
- """Return a set of (app, name) of applied migrations."""
- if self.has_table():
- return {tuple(x) for x in self.migration_qs.values_list('app', 'name')}
- else:
- # If the django_migrations table doesn't exist, then no migrations
- # are applied.
- return set()
-
- def record_applied(self, app, name):
- """Record that a migration was applied."""
- self.ensure_schema()
- self.migration_qs.create(app=app, name=name)
-
- def record_unapplied(self, app, name):
- """Record that a migration was unapplied."""
- self.ensure_schema()
- self.migration_qs.filter(app=app, name=name).delete()
-
- def flush(self):
- """Delete all migration records. Useful for testing migrations."""
- self.migration_qs.all().delete()
|
