CActiveRecordMetaData

public function __construct($model)
{
    $this->_modelClassName=get_class($model);

    $tableName=$model->tableName();
    if(($table=$model->getDbConnection()->getSchema()->getTable($tableName))===null)
        throw new CDbException(Yii::t('yii','The table "{table}" for active record class "{class}" cannot be found in the database.',
            array('{class}'=>$this->_modelClassName,'{table}'=>$tableName)));
            
    if(($modelPk=$model->primaryKey())!==null || $table->primaryKey===null)
    {
        $table->primaryKey=$modelPk;
        if(is_string($table->primaryKey) && isset($table->columns[$table->primaryKey]))
            $table->columns[$table->primaryKey]->isPrimaryKey=true;
        elseif(is_array($table->primaryKey))
        {
            foreach($table->primaryKey as $name)
            {
                if(isset($table->columns[$name]))
                    $table->columns[$name]->isPrimaryKey=true;
            }
        }
    }
    $this->tableSchema=$table;
    $this->columns=$table->columns;

    foreach($table->columns as $name=>$column)
    {
        if(!$column->isPrimaryKey && $column->defaultValue!==null)
            $this->attributeDefaults[$name]=$column->defaultValue;
    }

    foreach($model->relations() as $name=>$config)
    {
        $this->addRelation($name,$config);
    }
}

public function addRelation($name,$config)
{
    if(isset($config[0],$config[1],$config[2]))  // relation class, AR class, FK
        $this->relations[$name]=new $config[0]($name,$config[1],$config[2],array_slice($config,3));
    else
        throw new CDbException(Yii::t('yii','Active record "{class}" has an invalid configuration for relation "{relation}". It must specify the relation type, the related active record class and the foreign key.', array('{class}'=>$this->_modelClassName,'{relation}'=>$name)));
}

public function hasRelation($name)
{
    return isset($this->relations[$name]);
}

public function removeRelation($name)
{
    unset($this->relations[$name]);
}