framework/db/ActiveRecord.php
protected function deleteInternal()
    {
        if (!$this->beforeDelete()) {
            return false;
        }

        // we do not check the return value of deleteAll() because it's possible
        // the record is already deleted in the database and thus the method will return 0
        $condition = $this->getOldPrimaryKey(true);
        $lock = $this->optimisticLock();
        if ($lock !== null) {
            $condition[$lock] = $this->$lock;
        }
        $result = static::deleteAll($condition);
        if ($lock !== null && !$result) {
            throw new StaleObjectException('The object being deleted is outdated.');
        }
        $this->setOldAttributes(null);
        $this->afterDelete();

        return $result;
    }
protected function deleteInternal()
    {
        if (!$this->beforeDelete()) {
            return false;
        }

        // we do not check the return value of deleteAll() because it's possible
        // the record is already deleted in the database and thus the method will return 0
        $condition = $this->getOldPrimaryKey(true);
        $lock = $this->optimisticLock();
        if ($lock !== null) {
            $condition[$lock] = $this->$lock;
        }
        $result = static::deleteAll($condition);
        if ($lock !== null && !$result) {
            throw new StaleObjectException('The object being deleted is outdated.');
        }
        $this->setOldAttributes(null);
        $this->afterDelete();

        return $result;
    }
Deletes an ActiveRecord without considering transaction.
@return int|false the number of rows deleted, or `false` if the deletion is unsuccessful for some reason.
Note that it is possible the number of rows deleted is 0, even though the deletion execution is successful.
@throws StaleObjectException