The map and reduce functions for a Couchbase view to show the stats on the size of the documents in a bucket grouped by the key prefix when it is either an underscore or colon.

Map.js

function (doc, meta) {

  // calculate the size of the document
  var size;
  if (meta.type == "json") {
    size = JSON.stringify(doc).length;
  } else if (meta.type == "base64") {
    size = decodeBase64(doc).length;
  }

  // try to figure out the separator
  
  // try underscore first
  var firstSeparator = meta.id.indexOf('_');
  
  // try colon second
  firstSeparator = (firstSeparator > -1) ? firstSeparator : meta.id.indexOf(':');

  // use the firstKeyPart when possible
  if (firstSeparator > -1) {
    var firstKeyPart = meta.id.substring(0, firstSeparator);
    emit(firstKeyPart, size);
  } else {
    emit('n/a', size);
  }
  
}

Reduce.js

function (keys, values, rereduce) {

  function createResult() {
    return {
      sum: 0,
      cnt: 0,
      avg: 0,
      min: false,
      max: false,
    };
  }

  var result = {};
  if (rereduce) {
   	
    values.forEach(function (v) {
      for (var k in v) {
        
        // try to get the result associated with this key
        var keyResult = result[k];
        
        // when it doesn't exist then init default
        if (!keyResult) {
          keyResult = createResult();
          result[k] = keyResult;
        }
        
        // get this result
        var valueResult = v[k];
        
        // merge all values
        keyResult.cnt += valueResult.cnt;
        keyResult.sum += valueResult.sum;
        keyResult.min = keyResult.min === false ? valueResult.min : Math.min(keyResult.min, valueResult.min);
        keyResult.max = keyResult.max === false ? valueResult.max : Math.max(keyResult.max, valueResult.max);  
      }
      
    });    
    
  } else {

    for (var i = 0; i < keys.length; i++) {
    
      var key = keys[i];
      var value = values[i];
      
      // build the result for this key
      var keyResult = createResult();
      result[key] = keyResult;
      
      // increment the values
      keyResult.cnt++;
      keyResult.sum += value;
      keyResult.min = keyResult.min === false ? value : Math.min(keyResult.min, value);
      keyResult.max = keyResult.max === false ? value : Math.max(keyResult.max, value);
    
    }
    
  }
  
  // set the avg
  for (var k in result) {
    var keyResult = result[k];
    keyResult.avg = keyResult.sum / keyResult.cnt;     
  }
  
  return result;
  
}