MAP products bought together in CouchDB and create facets via REDUCE

map.js

function(doc) {
  if (doc.type === "sale") {
    if (doc.register_sale_products && doc.register_sale_products.length>1) {
      for (var i=0; i < doc.register_sale_products.length; i++) {
        for (var j=0; j < doc.register_sale_products.length; j++) {
          if (i != j) {
            emit([doc.register_sale_products[i].name,
                  doc.register_sale_products[j].name],
                  1)
}}}}}}

reduce.js

function(keys, values) {
   return sum(values);
}