How to get from CouchDB only certain fields of certain documents with a single request?

Question

create a view that return only a subset of values from a document, each with its key and value within a json string. like if one given view returns a document as this following,

Answer 1

A map function that emits a new document with selected fields only. As an example, let's map field1 (a string) and field9 (an array) only:

function map(doc) {
  emit(doc._id, {
    field1: doc.field1, 
    field9: doc.field9
  });
}

In the above example, each document will be fired with a key being the original doc ID and the value being the mapped fields you require. This is useful if you are planning to add a reduce function later.

Depending on your use case, you may just want to emit the mapped objects:

function map(doc) {
  emit({
    field1: doc.field1, 
    field9: doc.field9
  });
}

Please see http://guide.couchdb.org/draft/views.html The documentation on building data views is pretty good, you can discover a lot by experimenting..