lib/mosql/schema.rb in mosql-0.4.0 vs lib/mosql/schema.rb in mosql-0.4.1

@@ -157,14 +157,28 @@
       end
 
       val
     end
 
-    def fetch_special_source(obj, source)
+    def fetch_exists(obj, dotted)
+      pieces = dotted.split(".")
+      while pieces.length > 1
+        key = pieces.shift
+        obj = obj[key]
+        return false unless obj.is_a?(Hash)
+      end
+      obj.has_key?(pieces.first)
+    end
+
+    def fetch_special_source(obj, source, original)
       case source
       when "$timestamp"
         Sequel.function(:now)
+      when /^\$exists (.+)/
+        # We need to look in the cloned original object, not in the version that
+        # has had some fields deleted.
+        fetch_exists(original, $1)
       else
         raise SchemaError.new("Unknown source: #{source}")
       end
     end
 
@@ -186,18 +200,23 @@
     end
 
     def transform(ns, obj, schema=nil)
       schema ||= find_ns!(ns)
 
-      obj = obj.dup
+      original = obj
+
+      # Do a deep clone, because we're potentially going to be
+      # mutating embedded objects.
+      obj = BSON.deserialize(BSON.serialize(obj))
+
       row = []
       schema[:columns].each do |col|
 
         source = col[:source]
         type = col[:type]
 
         if source.start_with?("$")
-          v = fetch_special_source(obj, source)
+          v = fetch_special_source(obj, source, original)
         else
           v = fetch_and_delete_dotted(obj, source)
           case v
           when Hash
             v = JSON.dump(Hash[v.map { |k,v| [k, transform_primitive(v)] }])