Code generation
======================

Back to `doc index </products/d2a/>`__

Manually defining SQLAlchemy in the same way as Django models is bothersome,
and the definitions may diverge when changes occur.

`d2a` makes a sqlalchemy models file from all django models on your behalf.

Just use django command `sqla_codegen`. It will be available after the installation.

.. code-block:: shell

  $ python manage.py sqla_codegen [--path={output path}] [--template-path={template path}] [--db-type={database type}]


.. warning::

  - Do not use with `Auto loading </products/d2a/features/autoload.html>`__.

    - `AUTOLOAD` is normally disabled but gets enabled when set dict object to ``settings.D2A_CONFIG["AUTOLOAD"]``.


Example
---------------------

- `models_sqla_example.py <https://github.com/walkframe/d2a/blob/master/project_postgresql/models_sqla_example.py>`__

  - This file was made by ``$ ./manage.py sqla_codegen --settings=settings.codegen --path=models_sqla_example.py``.
  - `settings/codegen.py <https://github.com/walkframe/d2a/blob/master/project_postgresql/settings/codegen.py>`__

    - `Project configuration </products/d2a/config.html>`__


Command options
---------------------
All options are optional.

:`--path`:

  The file will be stored into this path.

  By default `d2a` makes a `models_sqla.py` at your django project root.


:`--template-path`:

  To make it versatile, `d2a` allows the developer to customize template.
  Specify the relative file path from `settings.TEMPLATES`

  Current original template is `here <https://github.com/walkframe/d2a/blob/master/project_postgresql/original_template.tmpl>`__

  Example:

    You can get also schemas from `Table` suffix like the following:
  
    .. code-block:: python

      # Code generated by d2a (https://github.com/walkframe/d2a).
      # `{{ command }}` at {{ generated_at }}.
      
      {{ blocks.before_importing }}
      from importlib import import_module
      
      import sqlalchemy as sa
      from sqlalchemy import types as default_types
      from sqlalchemy.dialects import (
          postgresql as postgresql_types,
          mysql as mysql_types,
          oracle as oracle_types,
      )
      from sqlalchemy.ext.declarative import declarative_base
      try:
          from geoalchemy2 import types as geotypes
      except ImportError:
          pass
      
      {{ blocks.after_importing }}
      
      Base = declarative_base()
      
      
      class CIText(default_types.String):
          '''DO NOT DELETE THIS CLASS'''
          __visit_name__ = 'CITEXT'
      
      
      def GET_DEFAULT(path):
          '''DO NOT DELETE THIS FUNCTION'''
      
          module_path, model_name, field_name = path.rsplit(".", 2)
          try:
              module = import_module(module_path)
              model = getattr(module, model_name)
          except (ImportError, AttributeError):
              return None
      
          for field in model._meta.fields:
              if field.name == field_name:
                  return field.default
      
      
      {{ blocks.before_models }}
      
      
      {% for model in models %}
      class {{ model.model_name }}(Base):
          __tablename__ = '{{ model.table_name }}'
          {% for name, args in model.columns.items %}
          {{ name }} = sa.Column({% for arg in args %}
              {{ arg | safe }},{% endfor %}
          ){% endfor %}{% for name, args in model.relationships.items %}
          {{ name }} = sa.orm.relationship({% for arg in args %}
              {{ arg | safe }},{% endfor %}
          ){% endfor %}
      
      
      {{ model.model_name }}Table = {{ model.model_name }}.__table__
      {% endfor %}
      {{ blocks.after_models }}

    ..warning::

      Deleting `CIText` and `GET_DEFAULT` is prohibited.


:`--db-type`:

  You can select a type of database, it affects sqlalchemy field types of models. 
  
  Available options:
  
  - `default`
  - `postgresql`
  - `mysql`
  - `oracle`
  
  When you do not specify this option, `d2a` will judge the type from django settings automatically.
  So you do not have to specify this option usually.