Cgridview CLinkPager返回一个小于pageSize中指定的记录

I am using CGridView in application and setting pageSize to 10 but on loading the page it shows 9 records.

Here is my code:

Model Function returning data:

  public function myTasks()
    {
        $criteria = new CDbCriteria();
        $criteria->select = "*";
        $criteria->join = 'LEFT JOIN task_assignment t2 on t.id=t2.task_id';
        $criteria->condition = "t2.task_id is NULL  AND t.user_id=" . Yii::app()->user->id;
        $criteria->compare('t.task_title', $this->task_title, true);
        $criteria->compare('t.task_description', $this->task_description, true);
        $criteria->compare('t.project_id', $this->project_id, true);
        $criteria->addCondition("t.status!='Deleted'");
        $criteria->distinct = true;
        $criteria->order = 'id desc';

        return new CActiveDataProvider('Task', array(
            'criteria' => $criteria,
            'pagination' => array(
                'pageSize' => 10
            ),
        ));
    }

Here is my view:

Yii::app()->clientscript->scriptMap['jquery.js'] = FALSE;
$this->widget('zii.widgets.grid.CGridView', array(
    'dataProvider' => $model->myTasks(),
    'summaryText' => '',
    'emptyText' => 'There are no tasks to dispaly',
    'itemsCssClass' => 'table table-striped',
    'pagerCssClass' => 'dataTables_paginate paging_bootstrap text-center paginationBg',
    'pager' => array(
        'prevPageLabel' => '‹  Previous',
        'nextPageLabel' => 'Next  ›',
        'firstPageLabel' => '«  First',
        'lastPageLabel' => 'Last  »',
        'header' => '',
        'htmlOptions' => array('class' => 'pagination')

    ),
    'htmlOptions' => array(
        'class' => 'table-responsive',
        'id' => "my-task-grid"
    ),
    'columns' => array(
        array(
            'name' => 'task_title',
            'value' => '$data->task_title',
            'type' => 'raw',
        )
    )
));

Also if I click page number 2 and then click on page 1 back then it returns correct 10 results.

Any ideas? Thanks for your help.