Question

Is it possible to change the limits of a Query without executing it again.

Here is my code:

$this->db->select("SQL_CALC_FOUND_ROWS e.emp_no, e.birth_date, e.first_name, e.last_name, e.gender, e.hire_date, t.title, s.salary, d.dept_name", FALSE)
            ->from('employees AS e')
            ->join('titles AS t', 'e.emp_no = t.emp_no')
            ->join('salaries AS s', 't.emp_no = s.emp_no')
            ->join('dept_emp AS de', 's.emp_no = de.emp_no')
            ->join('departments AS d', 'de.dept_no = d.dept_no')
            ->join('dept_manager AS dm', 'd.dept_no = dm.dept_no')
            ->order_by($sort_by, $sort_order)
            ->group_by('e.emp_no')
            ->where('t.title', $title)
                        ->limit($limit, $offset);


    $ret['rows'] = $q->get()->result(); 

I am using pagination so if I keep loading a query that return about 100,000 rows it slows down the return.

I wanted to make it faster by running the query once then changing the limit dynamically.

Answer 1

The limit doesn’t slow down your application. “SQL_CALC_FOUND_ROWS” does. It’s known fact that it can slow down a query, and i mean SLOW. Check this post for benchmarks and explanation of how it works: http://www.mysqlperformanceblog.com/2007/08/28/to-sql_calc_found_rows-or-not-to-sql_calc_found_rows/