title: Mysql Query takes too much time to execute
body: <p>So I have to tables, <code>products_used</code> aprox 600MB and <code>products_language_description</code> which is about 5MB, but the thing is that this query never finishes running...</p>
  
  <p>I have tried REPAIR,OPTIMIZE ANALYZE, I'm out of ideas how to improve this...</p>
  
  <pre><code>SELECT pu.products_id, count(pu.products_id) as products_count, p.products_name,
  pu.time_used FROM products_used pu, products_language_description p
  WHERE pu.merchant_id='69'
  AND p.products_id=pu.products_id GROUP BY products_id ORDER BY products_count
  DESC LIMIT 0, 20
  
  
  
  CREATE TABLE `products_used` (
      `products_used_id` INT(15) NOT NULL AUTO_INCREMENT,
      `plans_key` VARCHAR(255) NOT NULL DEFAULT '0',
      `products_id` BIGINT(20) NOT NULL DEFAULT '0',
      `customers_id` INT(10) NOT NULL DEFAULT '0',
      `merchant_id` INT(10) NOT NULL DEFAULT '0',
      `time_used` DATETIME NOT NULL DEFAULT '0000-00-00 00:00:00',
      PRIMARY KEY (`products_used_id`),
      INDEX `plans_key` (`plans_key`)
  )
  COLLATE='latin1_swedish_ci'
  ENGINE=MyISAM
  AUTO_INCREMENT=24625441;
  
  CREATE TABLE `products_language_description` (
      `products_id` INT(5) NOT NULL DEFAULT '0',
      `products_description` LONGTEXT NOT NULL,
      `products_name` TEXT NOT NULL COLLATE 'utf8_general_ci',
      `products_help_info` LONGBLOB NOT NULL,
      `products_language` VARCHAR(255) NOT NULL DEFAULT '',
      PRIMARY KEY (`products_id`, `products_language`)
  )
  COLLATE='latin1_swedish_ci'
  ENGINE=MyISAM;
  </code></pre>