The preceding map function we just wrote has a limitation—it will identify only those last names where the desired name appears before the hyphen. Therefore, the last name Van Der Beek-Moody would not be found. To address this issue, we could query a second time, with the startkey and endkey parameters reversed from our previous query. However, there is a better way.

There is no rule that a document must have only one key per row in an index. Therefore, we can rewrite our index to emit an index row for every possible last name. In this example, a possible last name is anything appearing before or after a hyphen:

function(doc, meta) {
  if (doc.type == "user" && doc.lastName) {
    var parts = doc.lastName.split("-");
    for(vari = 0; i<parts.length; i++) {
      emit(parts[i], null);
    }
  }
}

In this new map function, we use JavaScript's string split() function to return each of the names contained in a last name. For each match name we find, we send...