public function primary(/*# string */ $conflictClause = '')
    {
        $col = &$this->col_defs[count($this->col_defs) - 1];
        $col['primary'] = $conflictClause;
        return $this;
    }
public function primary(/*# string */ $conflictClause = '')
    {
        $col = &$this->col_defs[count($this->col_defs) - 1];
        $col['primary'] = $conflictClause;
        return $this;
    }
{@inheritDoc}