Assume labels are correct in ListChanges

To reduce end-user latency when displaying changes in a search result
or user dashboard, assume the labels are accurate in the database at
display time and don't recompute the access privileges of a reviewer.

Change-Id: I1316adf627e88fdcde1cd845444d56da9abaeb57

gerrit-server/src/main/java/com/google/gerrit/server/project/ChangeControl.java

@@ -292,11 +292,11 @@ public class ChangeControl {
   }
 
   public List<SubmitRecord> canSubmit(ReviewDb db, PatchSet patchSet) {
-    return canSubmit(db, patchSet, null);
+    return canSubmit(db, patchSet, null, false);
   }
 
   public List<SubmitRecord> canSubmit(ReviewDb db, PatchSet patchSet,
-      @Nullable ChangeData cd) {
+      @Nullable ChangeData cd, boolean fastEvalLabels) {
     if (change.getStatus().isClosed()) {
       SubmitRecord rec = new SubmitRecord();
       rec.status = SubmitRecord.Status.CLOSED;
@@ -353,6 +353,10 @@ public class ChangeControl {
             + getProject().getName());
       }
 
+      if (fastEvalLabels) {
+        env.once("gerrit", "assume_range_from_label");
+      }
+
       try {
         for (Term[] template : env.all(
             "gerrit", "can_submit",
@@ -391,6 +395,10 @@ public class ChangeControl {
             parentEnv.once("gerrit", "locate_submit_filter", new VariableTerm());
         if (filterRule != null) {
           try {
+            if (fastEvalLabels) {
+              env.once("gerrit", "assume_range_from_label");
+            }
+
             Term resultsTerm = toListTerm(results);
             results.clear();
             Term[] template = parentEnv.once(

gerrit-server/src/main/java/com/google/gerrit/server/query/change/ListChanges.java

@@ -226,7 +226,7 @@ public class ListChanges {
 
     PatchSet ps = cd.currentPatchSet(db);
     Map<String, LabelInfo> labels = Maps.newLinkedHashMap();
-    for (SubmitRecord rec : ctl.canSubmit(db.get(), ps, cd)) {
+    for (SubmitRecord rec : ctl.canSubmit(db.get(), ps, cd, true)) {
       if (rec.labels == null) {
         continue;
       }

gerrit-server/src/main/prolog/gerrit_common.pl

@@ -25,8 +25,7 @@
 %%   predicate that needs to obtain it.
 %%
 init :-
-  define_hash(commit_labels),
+  define_hash(commit_labels).
-  define_hash(current_user).
 
 define_hash(A) :- hash_exists(A), !, hash_clear(A).
 define_hash(A) :- atom(A), !, new_hash(_, [alias(A)]).
@@ -97,6 +96,10 @@ index_commit_labels([_ | Rs]) :-
 %%
 %%   Lookup the range allowed to be used.
 %%
+user_label_range(Label, Who, Min, Max) :-
+  hash_get(commit_labels, '$fast_range', true), !,
+  atom(Label),
+  assume_range_from_label(Label, Who, Min, Max).
 user_label_range(Label, Who, Min, Max) :-
   Who = user(_), !,
   atom(Label),
@@ -106,6 +109,14 @@ user_label_range(Label, test_user(Name), Min, Max) :-
   clause(user:test_grant(Label, test_user(Name), range(Min, Max)), _)
   .
 
+assume_range_from_label :-
+  hash_put(commit_labels, '$fast_range', true).
+
+assume_range_from_label(Label, Who, Min, Max) :-
+  commit_label(label(Label, Value), Who), !,
+  Min = Value, Max = Value.
+assume_range_from_label(_, _, 0, 0).
+
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%