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新しいDjango=移行でモデルに新しいフィールドを追加するには？

contribute_to_classメソッドを使用していますが、新しい移行でデータベースにフィールドを作成する方法がわかりません。

djangodjango-modelsdjango-1.7django-migrations
25
pedro_witoi

Django 1.7で導入された新しい移行で質問に答えるために、モデルに新しいフィールドを追加するには、そのフィールドをモデルに追加し、./manage.py makemigrationsおよび次に./manage.py migrateを実行すると、新しいフィールドがDBに追加されます。

ただし、既存のモデルのエラーを処理しないようにするには、--fakeを使用できます。

  1. 既存のモデルの移行を初期化します。

    ./manage.py makemigrations myapp

  2. 既存のモデルの偽の移行：

    ./manage.py migrate --fake myapp

  3. 新しいフィールドをmyapp.modelsに追加します。

    from Django.db import models

class MyModel(models.Model):
    ... #existing fields
    newfield = models.CharField(max_length=100) #new field

  4. Makemigrationsを再度実行します（これにより、移行フィールドに新しい移行ファイルが追加され、dbにnewfieldが追加されます）。

    ./manage.py makemigrations myapp

  5. 移行を再度実行します。

    ./manage.py migrate myapp
62
Nima

これを実行し、モデルが属するアプリケーション内に移行を配置するのではなく、実際にフィールドを追加するアプリケーションに移行ファイルを配置するには、独自のMigration基本クラスを作成する必要がありました。

元のモデルと同じアプリケーション内で_contribute_to_class_を使用すると、@ _ nimaの答えは完全に機能しますが、_contribute_to_class_を使用する意味はわかりません。

これがコードです。これは、モデルを_self.migrated_app_ではなく_self.app_label_から移行するように適合されたDjangoの元のコードです。

_from Django.db import migrations


class Migration(migrations.Migration):

  migrated_app = None

  def __init__(self, name, app_label):
    super(Migration,self).__init__(name, app_label)
    if self.migrated_app is None:
      self.migrated_app = self.app_label

  def mutate_state(self, project_state):
    new_state = project_state.clone()
    for operation in self.operations:
        operation.state_forwards(self.migrated_app, new_state)
    return new_state

  def apply(self, project_state, schema_editor, collect_sql=False):
    for operation in self.operations:
      if collect_sql and not operation.reduces_to_sql:
        schema_editor.collected_sql.append("--")
        schema_editor.collected_sql.append("-- MIGRATION NOW PERFORMS OPERATION THAT CANNOT BE WRITTEN AS SQL:")
        schema_editor.collected_sql.append("-- %s" % operation.describe())
        schema_editor.collected_sql.append("--")
        continue
      new_state = project_state.clone()
      operation.state_forwards(self.migrated_app, new_state)
      if not schema_editor.connection.features.can_rollback_ddl and operation.atomic:
        with atomic(schema_editor.connection.alias):
          operation.database_forwards(self.migrated_app, schema_editor, project_state, new_state)
      else:
        operation.database_forwards(self.migrated_app, schema_editor, project_state, new_state)
      project_state = new_state
    return project_state

  def unapply(self, project_state, schema_editor, collect_sql=False):
    to_run = []
    for operation in self.operations:
      if collect_sql and not operation.reduces_to_sql:
        schema_editor.collected_sql.append("--")
        schema_editor.collected_sql.append("-- MIGRATION NOW PERFORMS OPERATION THAT CANNOT BE WRITTEN AS SQL:")
        schema_editor.collected_sql.append("-- %s" % operation.describe())
        schema_editor.collected_sql.append("--")
        continue
      if not operation.reversible:
        raise Migration.IrreversibleError("Operation %s in %s is not reversible" % (operation, self))
      new_state = project_state.clone()
      operation.state_forwards(self.migrated_app, new_state)
      to_run.append((operation, project_state, new_state))
      project_state = new_state
    to_run.reverse()
    for operation, to_state, from_state in to_run:
      if not schema_editor.connection.features.can_rollback_ddl and operation.atomic:
        with atomic(schema_editor.connection.alias):
          operation.database_backwards(self.migrated_app, schema_editor, from_state, to_state)
      else:
        operation.database_backwards(self.migrated_app, schema_editor, from_state, to_state)
    return project_state
_

_base.utils_にあるこの新しい移行クラスを使用すると、手書きの移行は次のようになります。また、Django "間違った"アプリケーション内に移行を記述し、ファイルを移動して更新し、カスタムMigrationクラスを使用することもできます。

_# -*- coding: utf-8 -*-
from __future__ import unicode_literals

from Django.db import models, migrations
from base.utils import Migration
import dynamicsites.fields


class Migration(Migration):

    dependencies = [
        ('sites', '0001_initial'),
        ('base', '0001_initial'),
    ]

    migrated_app = 'sites'

    operations = [
        migrations.AddField(
            model_name='site',
            name='folder_name',
            field=dynamicsites.fields.FolderNameField(default='', help_text=b"Folder name for this site's files.  The name may only consist of lowercase characters, numbers (0-9), and/or underscores", max_length=64, blank=True),
            preserve_default=False,
        ),
        migrations.AddField(
            model_name='site',
            name='subdomains',
            field=dynamicsites.fields.SubdomainListField(default=(), help_text=b'Comma separated list of subdomains this site supports.  Leave blank to support all subdomains', blank=True),
            preserve_default=False,
        ),
    ]
_

Django 1.8のカスタム移行クラス

_from Django.db import migrations


class Migration(migrations.Migration):

  migrated_app = None

  def __init__(self, name, app_label):
    super(Migration,self).__init__(name, app_label)
    if self.migrated_app is None:
      self.migrated_app = self.app_label

  def __eq__(self, other):
    if not isinstance(other, Migration):
      if not isinstance(other, migrations.Migration):
        return False
      return (self.name == other.name) and (self.migrated_app == other.app_label)
    return (self.name == other.name) and (self.migrated_app == other.migrated_app)

  def __hash__(self):
    return hash("%s.%s" % (self.app_label, self.name))

  def mutate_state(self, project_state, preserve=True):
    new_state = project_state
    if preserve:
      new_state = project_state.clone()

    for operation in self.operations:
      operation.state_forwards(self.migrated_app, new_state)
    return new_state

  def apply(self, project_state, schema_editor, collect_sql=False):
    for operation in self.operations:
      if collect_sql and not operation.reduces_to_sql:
        schema_editor.collected_sql.append("--")
        schema_editor.collected_sql.append("-- MIGRATION NOW PERFORMS OPERATION THAT CANNOT BE "
                                           "WRITTEN AS SQL:")
        schema_editor.collected_sql.append("-- %s" % operation.describe())
        schema_editor.collected_sql.append("--")
        continue
      old_state = project_state.clone()
      operation.state_forwards(self.migrated_app, project_state)
      if not schema_editor.connection.features.can_rollback_ddl and operation.atomic:
        with atomic(schema_editor.connection.alias):
          operation.database_forwards(self.migrated_app, schema_editor, old_state, project_state)
      else:
        operation.database_forwards(self.migrated_app, schema_editor, old_state, project_state)
    return project_state

  def unapply(self, project_state, schema_editor, collect_sql=False):
    to_run = []
    new_state = project_state
    for operation in self.operations:
      if not operation.reversible:
        raise Migration.IrreversibleError("Operation %s in %s is not reversible" % (operation, self))
      new_state = new_state.clone()
      old_state = new_state.clone()
      operation.state_forwards(self.migrated_app, new_state)
      to_run.insert(0, (operation, old_state, new_state))

    for operation, to_state, from_state in to_run:
      if collect_sql:
        if not operation.reduces_to_sql:
          schema_editor.collected_sql.append("--")
          schema_editor.collected_sql.append("-- MIGRATION NOW PERFORMS OPERATION THAT CANNOT BE "
                                             "WRITTEN AS SQL:")
          schema_editor.collected_sql.append("-- %s" % operation.describe())
          schema_editor.collected_sql.append("--")
          continue
      if not schema_editor.connection.features.can_rollback_ddl and operation.atomic:
        with atomic(schema_editor.connection.alias):
          operation.database_backwards(self.migrated_app, schema_editor, from_state, to_state)
      else:
        operation.database_backwards(self.migrated_app, schema_editor, from_state, to_state)
      return project_state
_
6
Emma

次のように作成できます。

from Django.db.models import CharField
from Django.db.models.signals import class_prepared

def add_field(sender, **kwargs):
    """
    class_prepared signal handler that checks for the model named
    MyModel as the sender, and adds a CharField
    to it.
    """
    if sender.__name__ == "MyModel":
        field = CharField("New field", max_length=100)
        field.contribute_to_class(sender, "new_field")

class_prepared.connect(add_field)

詳細については、「 Django Model Field Injection 」を参照してください。

3
dhana