How to build "Tagging" support using CouchDB?

Question

I'm using the following view function to iterate over all items in the database (in order to find a tag), but I think the performance is very poor if the dataset is large. Any other approach?

def by_tag(tag):
return  '''
        function(doc) {
            if (doc.tags.length > 0) {
                for (var tag in doc.tags) {
                    if (doc.tags[tag] == "%s") {
                        emit(doc.published, doc)
                    }
                }
            }
        };
        ''' % tag

Answer 1

Disclaimer: I didn't test this and don't know if it can perform better.

Create a single perm view:

function(doc) {
  for (var tag in doc.tags) {
    emit([tag, doc.published], doc)
  }
};

And query with _view/your_view/all?startkey=['your_tag_here']&endkey=['your_tag_here', {}]

Resulting JSON structure will be slightly different but you will still get the publish date sorting.