Sphinx\SphinxClient::setGroupDistinct PHP Method

    public function setGroupDistinct($attribute)
    {
        if (!is_string($attribute)) {
            throw new \InvalidArgumentException('Attribute name must be a string.');
        }
        $this->groupdistinct = $attribute;
        return $this;
    }

 public function testResetGroupBy()
 {
     $sphinx = new SphinxClient();
     $sphinx->setGroupBy('attr', SphinxClient::SPH_GROUPBY_ATTR, '@group asc');
     $sphinx->setGroupDistinct('id');
     $sphinx->resetGroupBy();
     $this->assertSame($sphinx->groupby, '');
     $this->assertSame($sphinx->groupfunc, SphinxClient::SPH_GROUPBY_DAY);
     $this->assertSame($sphinx->groupsort, '@group desc');
     $this->assertSame($sphinx->groupdistinct, '');
 }