Compare "async" and "co" libraries

01_async.js

server.get('/queue/pending',function(req,res,next){
  var page = req.params.page || 1;
  page = page - 1;
  var per_page = req.params.per_page || 50;
  pool.getConnection(function(err,db){
    async.series([
      function(done){
        db.query(
          'SELECT COUNT(*) AS total FROM '+
          '(SELECT DISTINCT event, venue, event_time FROM import_queue '+
          'WHERE event_id IS NULL) A',
          [],
          done
        );
      },
      function(done){
        db.query(
          'SELECT DISTINCT event, venue, event_time, '+
          'MD5(CONCAT(event,venue,event_time)) AS hash, '+
          'COUNT(id) AS queue_count FROM import_queue '+
          'WHERE event_id IS NULL '+
          'GROUP BY event, venue, event_time ORDER BY queue_count DESC '+
          'LIMIT ?, ?',
          [ page*per_page, parseInt(per_page) ],
          done
        ) 
      } 
    ],function(err,results){
      db.release();
      var output = results[1][0];
      output.map(function(item){
        item.hash = item.hash.toString();
        return item;
      });
      res.json({
        total_rows: results[0][0][0].total,
        queued: output
      });
      next();
    });
  });
});

02_with_co.js

server.get('/queue/pending',function(req,res,next){
  var page = (req.params.page || 1) - 1;
  var per_page = req.params.per_page || 50;
  
  co(function *(){
    
    var pending_rows = yield query(
      'SELECT COUNT(*) AS total FROM '+
      '(SELECT DISTINCT event, venue, event_time FROM import_queue '+
      'WHERE event_id IS NULL) A',
      []  
    );    
          
    var queued_hashes = yield query(
      'SELECT DISTINCT event, venue, event_time, '+
      'MD5(CONCAT(event,venue,event_time)) AS hash, '+
      'COUNT(id) AS queue_count FROM import_queue '+
      'WHERE event_id IS NULL '+
      'GROUP BY event, venue, event_time ORDER BY queue_count DESC '+
      'LIMIT ?, ?',
      [ page*per_page, parseInt(per_page) ]
    );    
          
    res.json({
      total_rows: pending_rows[0].total,
      queued: queued_hashes.map(function(item){
        item.hash = item.hash.toString();
        return item;
      })
    });
    
  })(next);
      
});