Use transactions to handle comments when possible

If the database supports transactions (see gwtorm, not all do)
try to perform some update operations as a single transaction on
the change. This may allow the database to batch together any
record updates, saving some time.

Change-Id: I5af9efe3a541d83515109e3bf9a3497b3d8127de

gerrit-httpd/src/main/java/com/google/gerrit/httpd/rpc/patch/PatchDetailServiceImpl.java

@@ -110,6 +110,9 @@ class PatchDetailServiceImpl extends BaseServiceImplementation implements
       final AsyncCallback<VoidResult> callback) {
     run(callback, new Action<VoidResult>() {
       public VoidResult run(ReviewDb db) throws OrmException, Failure {
+        Change.Id id = commentKey.getParentKey().getParentKey().getParentKey();
+        db.changes().beginTransaction(id);
+        try {
           final PatchLineComment comment = db.patchComments().get(commentKey);
           if (comment == null) {
             throw new Failure(new NoSuchEntityException());
@@ -121,7 +124,11 @@ class PatchDetailServiceImpl extends BaseServiceImplementation implements
             throw new Failure(new IllegalStateException("Comment published"));
           }
           db.patchComments().delete(Collections.singleton(comment));
+          db.commit();
           return VoidResult.INSTANCE;
+        } finally {
+          db.rollback();
+        }
       }
     });
   }
@@ -142,6 +149,8 @@ class PatchDetailServiceImpl extends BaseServiceImplementation implements
         Account.Id account = getAccountId();
         AccountPatchReview.Key key =
             new AccountPatchReview.Key(patchKey, account);
+        db.accounts().beginTransaction(account);
+        try {
           AccountPatchReview apr = db.accountPatchReviews().get(key);
           if (apr == null && reviewed) {
             db.accountPatchReviews().insert(
@@ -149,7 +158,11 @@ class PatchDetailServiceImpl extends BaseServiceImplementation implements
           } else if (apr != null && !reviewed) {
             db.accountPatchReviews().delete(Collections.singleton(apr));
           }
+          db.commit();
           return VoidResult.INSTANCE;
+        } finally {
+          db.rollback();
+        }
       }
     });
   }

gerrit-httpd/src/main/java/com/google/gerrit/httpd/rpc/patch/SaveDraft.java

@@ -49,7 +49,6 @@ class SaveDraft extends Handler<PatchLineComment> {
     this.changeControlFactory = changeControlFactory;
     this.db = db;
     this.currentUser = currentUser;
-
     this.comment = comment;
   }
 
@@ -62,6 +61,9 @@ class SaveDraft extends Handler<PatchLineComment> {
     final Patch.Key patchKey = comment.getKey().getParentKey();
     final PatchSet.Id patchSetId = patchKey.getParentKey();
     final Change.Id changeId = patchKey.getParentKey().getParentKey();
+
+    db.changes().beginTransaction(changeId);
+    try {
       changeControlFactory.validateFor(changeId);
       if (db.patchSets().get(patchSetId) == null) {
         throw new NoSuchChangeException(changeId);
@@ -89,6 +91,7 @@ class SaveDraft extends Handler<PatchLineComment> {
         nc.setSide(comment.getSide());
         nc.setMessage(comment.getMessage());
         db.patchComments().insert(Collections.singleton(nc));
+        db.commit();
         return nc;
 
       } else {
@@ -97,7 +100,11 @@ class SaveDraft extends Handler<PatchLineComment> {
         }
         comment.updated();
         db.patchComments().update(Collections.singleton(comment));
+        db.commit();
         return comment;
       }
+    } finally {
+      db.rollback();
+    }
   }
 }

gerrit-server/src/main/java/com/google/gerrit/server/patch/PublishComments.java

@@ -116,18 +116,25 @@ public class PublishComments implements Callable<VoidResult> {
     }
     drafts = drafts();
 
+    db.changes().beginTransaction(changeId);
+    try {
       publishDrafts();
 
       final boolean isCurrent = patchSetId.equals(change.currentPatchSetId());
       if (isCurrent && change.getStatus().isOpen()) {
         publishApprovals(ctl);
-    } else if (! approvals.isEmpty()) {
+      } else if (!approvals.isEmpty()) {
         throw new InvalidChangeOperationException("Change is closed");
       } else {
         publishMessageOnly();
       }
 
       touchChange();
+      db.commit();
+    } finally {
+      db.rollback();
+    }
+
     email();
     fireHook();
     return VoidResult.INSTANCE;