Example map function with sample output and list function.

list-format.js

function(head, req){
  var i, 
      x, 
      results = {},
      headers = {},
      csv = [];
  while(x = getRow()){
    (function(row){
      var result = results[JSON.stringify(row.key)] || {};
      for(i in row.value){
        headers[i] = true;
        result[i] = row.value[i];
      }
      for(i in row.key){
        headers[i] = true;
        result[i] = row.key[i];
      }
      results[JSON.stringify(row.key)] = result;
    })(x);
  }
  headers = Object.keys(headers);
  for(i in results){
    csv.push(results[i]);
  }
  csv = csv.map(function(row){
    var csv_row = [];
    for(i in headers){
      var header = headers[i];
      csv_row.push(row[header]);
    }
    return csv_row;
  });
  csv.unshift(headers);
  send(csv.map(function(row){
    return row.join(',');
  }).join('\n'));
}

list-output.csv

map-output.json

{
  "total_rows": 10000,
  "offset": 1,
  "rows": [
    {
      "id": "8a41c8ae025a90c8d748aeb71746ef71",
      "key": {
        "studyId": 1,
        "subjectId": "0",
        "eventId": "SCR"
      },
      "value": {
        "1000": "female",
        "1001": " 22 ",
        "1002": "10-Oct-2012"
      }
    }
  ]
}

map.js

function (doc) {
  if (doc.type == "record" && doc.deleted !== true) {
    var i,
        keys = {},
        values = {};

    if (doc.studyId) {
      keys.studyId = doc.studyId;
      for (i in doc.mappingRules) {
        var mappingRule = doc.mappingRules[i],
            columnId = require('views/lib/module').test(doc, mappingRule.sourceColumn);

        switch(mappingRule.columnType){
          case "subject":
            keys.subjectId = columnId;
            break;
          case "event":
            keys.eventId = columnId;
            break;
          case "variable":
            values[mappingRule.variableId] = columnId;
            break;
        }
      }

      emit(keys, values);
    }
  }
}