The map and reduce functions for Couchbase View to count the prefix of a cache key separated with an underscore.

Map.js

function (doc, meta) {
  	var firstSeparator = meta.id.indexOf('_');
    if (firstSeparator > -1) {
      var firstKeyPart = meta.id.substring(0, firstSeparator);
      emit(firstKeyPart, null);
    } else {
      emit('n/a', null);
    }
}

Reduce.js

function (keys, values, rereduce) {
  var result = {}
  if (rereduce) {
   	values.forEach(function (v) {
    	for(var n in v) {
        result[n] = (result[n] || 0) + v[n];
      }
    });
  } else {    
    keys.forEach(function (k) {
    	result[k] = (result[k] || 0) + 1;
    });
  }
  return result;
}