Set PerThreadCache as readonly after merging a change

Apply the same optimisation made for Change-Id: I1b71bfcf to
the production of events after merging a change and for returning
the merged change JSON response.

The same considerations of performance improvement and reduction
of /meta refs lookup are valid in this use-case.

Release-Notes: enable the read-only cache of /meta refs for merged changes
Change-Id: I34e147d644dfcdb5a6b1baa32cd4347805e506fc

3 files changed, 28 insertions, 15 deletions

diff --git a/java/com/google/gerrit/server/events/StreamEventsApiListener.java b/java/com/google/gerrit/server/events/StreamEventsApiListener.java
index 272c835c0b..413269a6fa 100644
--- a/java/com/google/gerrit/server/events/StreamEventsApiListener.java
+++ b/java/com/google/gerrit/server/events/StreamEventsApiListener.java
@@ -441,14 +441,18 @@ public class StreamEventsApiListener
   @Override
   public void onChangeMerged(ChangeMergedListener.Event ev) {
     try {
-      ChangeNotes notes = getNotes(ev.getChange());
-      Change change = notes.getChange();
-      ChangeMergedEvent event = new ChangeMergedEvent(change);
+      ChangeMergedEvent event;
+      Change change;
+      try (ReadonlyRequestWindow window = PerThreadCache.openReadonlyRequestWindow()) {
+        ChangeNotes notes = getNotes(ev.getChange());
+        change = notes.getChange();
+        event = new ChangeMergedEvent(change);
 
-      event.change = changeAttributeSupplier(change, notes);
-      event.submitter = accountAttributeSupplier(ev.getWho());
-      event.patchSet = patchSetAttributeSupplier(change, psUtil.current(db.get(), notes));
-      event.newRev = ev.getNewRevisionId();
+        event.change = changeAttributeSupplier(change, notes);
+        event.submitter = accountAttributeSupplier(ev.getWho());
+        event.patchSet = patchSetAttributeSupplier(change, psUtil.current(db.get(), notes));
+        event.newRev = ev.getNewRevisionId();
+      }
 
       dispatcher.run(d -> d.postEvent(change, event));
     } catch (OrmException e) {
diff --git a/java/com/google/gerrit/server/extensions/events/ChangeMerged.java b/java/com/google/gerrit/server/extensions/events/ChangeMerged.java
index 7b814aed0f..1f14db399f 100644
--- a/java/com/google/gerrit/server/extensions/events/ChangeMerged.java
+++ b/java/com/google/gerrit/server/extensions/events/ChangeMerged.java
@@ -24,6 +24,8 @@ import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.server.GpgException;
 import com.google.gerrit.server.account.AccountState;
+import com.google.gerrit.server.cache.PerThreadCache;
+import com.google.gerrit.server.cache.PerThreadCache.ReadonlyRequestWindow;
 import com.google.gerrit.server.patch.PatchListNotAvailableException;
 import com.google.gerrit.server.patch.PatchListObjectTooLargeException;
 import com.google.gerrit.server.permissions.PermissionBackendException;
@@ -52,14 +54,18 @@ public class ChangeMerged {
     if (listeners.isEmpty()) {
       return;
     }
+
     try {
-      Event event =
-          new Event(
-              util.changeInfo(change),
-              util.revisionInfo(change.getProject(), ps),
-              util.accountInfo(merger),
-              newRevisionId,
-              when);
+      Event event;
+      try (ReadonlyRequestWindow window = PerThreadCache.openReadonlyRequestWindow()) {
+        event =
+            new Event(
+                util.changeInfo(change),
+                util.revisionInfo(change.getProject(), ps),
+                util.accountInfo(merger),
+                newRevisionId,
+                when);
+      }
       listeners.runEach(l -> l.onChangeMerged(event));
     } catch (PatchListObjectTooLargeException e) {
       logger.atWarning().log("Couldn't fire event: %s", e.getMessage());
diff --git a/java/com/google/gerrit/server/restapi/change/Submit.java b/java/com/google/gerrit/server/restapi/change/Submit.java
index a775c9399f..0839534d8a 100644
--- a/java/com/google/gerrit/server/restapi/change/Submit.java
+++ b/java/com/google/gerrit/server/restapi/change/Submit.java
@@ -43,6 +43,8 @@ import com.google.gerrit.server.IdentifiedUser;
 import com.google.gerrit.server.PatchSetUtil;
 import com.google.gerrit.server.ProjectUtil;
 import com.google.gerrit.server.account.AccountResolver;
+import com.google.gerrit.server.cache.PerThreadCache;
+import com.google.gerrit.server.cache.PerThreadCache.ReadonlyRequestWindow;
 import com.google.gerrit.server.change.ChangeJson;
 import com.google.gerrit.server.change.ChangeResource;
 import com.google.gerrit.server.change.RevisionResource;
@@ -214,7 +216,8 @@ public class Submit
     try (MergeOp op = mergeOpProvider.get()) {
       ReviewDb db = dbProvider.get();
       op.merge(db, change, submitter, true, input, false);
-      try {
+      try (ReadonlyRequestWindow readonlyRequestWindow =
+          PerThreadCache.openReadonlyRequestWindow()) {
         change =
             changeNotesFactory.createChecked(db, change.getProject(), change.getId()).getChange();
       } catch (NoSuchChangeException e) {