sql.py 文件源码

def sql_create(app_config, style, connection):
    "Returns a list of the CREATE TABLE SQL statements for the given app."

    check_for_migrations(app_config, connection)

    if connection.settings_dict['ENGINE'] == 'django.db.backends.dummy':
        # This must be the "dummy" database backend, which means the user
        # hasn't set ENGINE for the database.
        raise CommandError(
            "Django doesn't know which syntax to use for your SQL statements,\n"
            "because you haven't properly specified the ENGINE setting for the database.\n"
            "see: https://docs.djangoproject.com/en/%s/ref/settings/#databases" % get_docs_version()
        )

    # Get installed models, so we generate REFERENCES right.
    # We trim models from the current app so that the sqlreset command does not
    # generate invalid SQL (leaving models out of known_models is harmless, so
    # we can be conservative).
    app_models = list(app_config.get_models(include_auto_created=True))
    final_output = []
    tables = connection.introspection.table_names()
    known_models = set(model for model in connection.introspection.installed_models(tables) if model not in app_models)
    pending_references = {}

    for model in router.get_migratable_models(app_config, connection.alias, include_auto_created=True):
        output, references = connection.creation.sql_create_model(model, style, known_models)
        final_output.extend(output)
        for refto, refs in references.items():
            pending_references.setdefault(refto, []).extend(refs)
            if refto in known_models:
                final_output.extend(connection.creation.sql_for_pending_references(refto, style, pending_references))
        final_output.extend(connection.creation.sql_for_pending_references(model, style, pending_references))
        # Keep track of the fact that we've created the table for this model.
        known_models.add(model)

    # Handle references to tables that are from other apps
    # but don't exist physically.
    not_installed_models = set(pending_references.keys())
    if not_installed_models:
        alter_sql = []
        for model in not_installed_models:
            alter_sql.extend('-- ' + sql for sql in
                connection.creation.sql_for_pending_references(model, style, pending_references))
        if alter_sql:
            final_output.append('-- The following references should be added but depend on non-existent tables:')
            final_output.extend(alter_sql)

    return final_output