createdAt kept during any kind of update

lib/datastore.js

@@ -590,7 +590,7 @@ Datastore.prototype._update = function (query, updateQuery, options, cb) {
     });
   }
   , function () {   // Perform the update
-    var modifiedDoc , modifications = [];
+    var modifiedDoc , modifications = [], createdAt;
 
     self.getCandidates(query, function (err, candidates) {
       if (err) { return callback(err); }
@@ -601,8 +601,12 @@ Datastore.prototype._update = function (query, updateQuery, options, cb) {
         for (i = 0; i < candidates.length; i += 1) {
           if (model.match(candidates[i], query) && (multi || numReplaced === 0)) {
             numReplaced += 1;
+            if (self.timestampData) { createdAt = candidates[i].createdAt; }
             modifiedDoc = model.modify(candidates[i], updateQuery);
-            if (self.timestampData) { modifiedDoc.updatedAt = new Date(); }
+            if (self.timestampData) {
+              modifiedDoc.createdAt = createdAt;
+              modifiedDoc.updatedAt = new Date();
+            }
             modifications.push({ oldDoc: candidates[i], newDoc: modifiedDoc });
           }
         }

test/db.test.js

@@ -1619,6 +1619,34 @@ describe('Database', function () {
       });
     });
 
+    it("createdAt property is unchanged and updatedAt correct after an update, even a complete document replacement", function (done) {
+      var d2 = new Datastore({ inMemoryOnly: true, timestampData: true });
+      d2.insert({ a: 1 });
+      d2.findOne({ a: 1 }, function (err, doc) {
+        var createdAt = doc.createdAt.getTime();
+
+        // Modifying update
+        setTimeout(function () {
+          d2.update({ a: 1 }, { $set: { b: 2 } }, {});
+          d2.findOne({ a: 1 }, function (err, doc) {
+            doc.createdAt.getTime().should.equal(createdAt);
+            assert.isBelow(Date.now() - doc.updatedAt.getTime(), 5);
+
+            // Complete replacement
+            setTimeout(function () {
+              d2.update({ a: 1 }, { c: 3 }, {});
+              d2.findOne({ c: 3 }, function (err, doc) {
+                doc.createdAt.getTime().should.equal(createdAt);
+                assert.isBelow(Date.now() - doc.updatedAt.getTime(), 5);
+
+                done();
+              });
+            }, 20);
+          });
+        }, 20);
+      });
+    });
+
   });   // ==== End of 'Update' ==== //