Remove invalidation flag and update last-update timestamp on task completion, not on metadata update

src/database-backends/postgresql/index.js

@@ -283,19 +283,12 @@ module.exports = function(state) {
 						return Promise.try(() => {
 							return getTaskResult(tx, task, id);
 						}).then((taskResult) => {
-							let sharedFields = {
-								isInvalidated: false,
-								updatedAt: new Date()
-							};
-
 							if (taskResult != null) {
 								return taskResult.$query(tx).patch({
-									... sharedFields,
 									metadata: update(taskResult.metadata),
 								});
 							} else {
 								return db.TaskResult.query(tx).insert({
-									... sharedFields,
 									task: task.name,
 									itemId: id,
 									metadata: update({})
@@ -333,7 +326,9 @@ module.exports = function(state) {
 						}).then((taskResult) => {
 							let sharedFields = {
 								isSuccessful: isSuccessful,
+								isInvalidated: false,
 								taskVersion: task.version,
+								updatedAt: new Date(),
 								expiresAt: (task.ttl != null)
 									? addMilliseconds(new Date(), task.ttl)
 									: undefined