Avoiding storing the 'id' key as a normal document attribute.

duplicates of the id were being stored (id and _id). Using select() to filter the schema

couchdb.lua

@@ -37,6 +37,19 @@ local function delegate(parent)
  return obj
 end
 
+
+-- util
+
+function select(tb, fun)
+ local ret = {}
+ for k,v in pairs(tb) do
+ if (fun(v,k)) then
+ ret[k] = v
+ end
+ end
+ return ret
+end
+
 -- Local functions
 
 local function _do_request(url, method, content)
@@ -89,8 +102,12 @@ end
 
 function create_document(schema)
  local obj = delegate(Document)
- obj.schema = schema
- obj.id = schema.id or obj.id
+ if schema.id then
+ obj.id = schema.id
+ obj.schema = select(obj, function(v,k) return k ~= 'id' end)
+ else
+ obj.schema = schema
+ end
  return obj
 end