Searching and Sorting by Count of Related Items in CGridView Follow @yiiframework

class Author extends CActiveRecord 
{
    ...
    function relations() {
        return array(
            'posts' => array(self::HAS_MANY, 'Post', 'author_id'),
        );
    }
    ...
}
 
class Post extends CActiveRecord 
{
    ...
}

$this->widget('zii.widgets.grid.CGridView', array(
    'dataProvider' => $model->search(),
    'filter' => $model,
    'columns' => array(
        'username',
        array(
            // 'name' => 'posts',
            'header' => 'Post Count',
            'value' => 'count($data->posts)',
        ),
    ),
));
// You can't use 'posts' relation as 'name' property.

class Author extends CActiveRecord 
{
    ...
    function relations() {
        return array(
            'posts' => array(self::HAS_MANY, 'Post', 'author_id'),
            'postCount' => array(self::STAT, 'Post', 'author_id'),
        );
    }
    ...
}
 
$this->widget('zii.widgets.grid.CGridView', array(
    'dataProvider' => $model->search(),
    'filter' => $model,
    'columns' => array(
        'username',
        'postCount',
    ),
));

class Author extends CActiveRecord 
{
    public $post_count;
    ...
    public function rules() {
        return array(
            ...
            array('username, xxx, yyy, post_count', 'safe', 'on' => 'search' ),
        );
    }
}

public function search() 
{
    $criteria=new CDbCriteria;
 
    // sub query to retrieve the count of posts
    $post_table = Post::model()->tableName();
    $post_count_sql = "(select count(*) from $post_table pt where pt.author_id = t.id)";
 
    // select
    $criteria->select = array(
        '*',
        $post_count_sql . " as post_count",
    );
 
    ...
    // where
    $criteria->compare($post_count_sql, $this->post_count);
    ...
 
    return new CActiveDataProvider(get_class($this), array(
        'criteria' => $criteria,
        'sort' => array(
            'defaultOrder' => 't.username',
                'attributes' => array(
                    ...
                    // order by
                    'post_count' => array(
                        'asc' => 'post_count ASC',
                        'desc' => 'post_count DESC',
                    ),
                    '*',
                ),
            ),
            'pagination' => array(
                'pageSize' => 20,
            ),
        ));
}

$this->widget('zii.widgets.grid.CGridView', array(
    'dataProvider' => $model->search(),
    'filter' => $model,
    'columns' => array(
        'username',
        'post_count',
        array(
            'class'=>'CButtonColumn',
        ),
    ),
));