Read mergeable bit from cache

Change callers on the client side to get this from ChangeInfo
(populated by ChangeJson) rather than Change.

Continue writing to the database, to facilitate online migration.

Change-Id: I7273e0253d357ff80aa3baf2b833419749b958ef

gerrit-common/src/main/java/com/google/gerrit/common/data/ChangeDetail.java

@@ -45,6 +45,7 @@ public class ChangeDetail {
   protected SubmitType submitType;
   protected SubmitTypeRecord submitTypeRecord;
   protected boolean canSubmit;
+  protected boolean mergeable;
   protected List<ChangeMessage> messages;
   protected PatchSet.Id currentPatchSetId;
   protected PatchSetDetail currentDetail;
@@ -274,4 +275,12 @@ public class ChangeDetail {
   public boolean canEdit() {
     return canEdit;
   }
+
+  public void setMergeable(boolean m) {
+    mergeable = m;
+  }
+
+  public boolean isMergeable() {
+    return mergeable;
+  }
 }

gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeDetailCache.java

@@ -91,6 +91,7 @@ public class ChangeDetailCache extends ListenableValue<ChangeDetail> {
     r.setChange(toChange(info));
     r.setStarred(info.starred());
     r.setPatchSets(toPatchSets(info));
+    r.setMergeable(info.mergeable());
     r.setMessages(toMessages(info));
     r.setAccounts(users(info));
     r.setCurrentPatchSetId(new PatchSet.Id(info.legacy_id(), rev._number()));
@@ -224,7 +225,6 @@ public class ChangeDetailCache extends ListenableValue<ChangeDetail> {
     c.setStatus(info.status());
     c.setCurrentPatchSet(p);
     c.setLastUpdatedOn(info.updated());
-    c.setMergeable(info.mergeable());
     return c;
   }
 

gerrit-gwtui/src/main/java/com/google/gerrit/client/changes/ChangeInfoBlock.java

@@ -125,7 +125,7 @@ public class ChangeInfoBlock extends Composite {
     if (Gerrit.getConfig().getNewFeatures()
         && (status.equals(Change.Status.NEW) || status.equals(Change.Status.DRAFT))) {
       table.getRowFormatter().setVisible(R_MERGE_TEST, true);
-      table.setText(R_MERGE_TEST, 1, chg.isMergeable() ? Util.C
+      table.setText(R_MERGE_TEST, 1, changeDetail.isMergeable() ? Util.C
           .changeInfoBlockCanMergeYes() : Util.C.changeInfoBlockCanMergeNo());
     } else {
       table.getRowFormatter().setVisible(R_MERGE_TEST, false);

gerrit-server/src/main/java/com/google/gerrit/server/change/MergeabilityCache.java

@@ -106,6 +106,12 @@ public class MergeabilityCache {
     };
   }
 
+  public static ObjectId toId(Ref ref) {
+    return ref != null && ref.getObjectId() != null
+        ? ref.getObjectId()
+        : ObjectId.zeroId();
+  }
+
   public static class EntryKey implements Serializable {
     private static final long serialVersionUID = 1L;
 
@@ -307,4 +313,10 @@ public class MergeabilityCache {
       return false;
     }
   }
+
+  public boolean getIfPresent(ObjectId commit, Ref intoRef,
+      SubmitType submitType, String mergeStrategy) {
+    return cache.getIfPresent(new EntryKey(
+        commit, toId(intoRef), submitType, mergeStrategy, null, null, null));
+  }
 }

gerrit-server/src/main/java/com/google/gerrit/server/change/Mergeable.java

@@ -14,8 +14,6 @@
 
 package com.google.gerrit.server.change;
 
-import static com.google.gerrit.extensions.common.SubmitType.CHERRY_PICK;
-
 import com.google.gerrit.common.data.SubmitTypeRecord;
 import com.google.gerrit.extensions.common.SubmitType;
 import com.google.gerrit.extensions.restapi.AuthException;
@@ -50,6 +48,7 @@ import org.slf4j.LoggerFactory;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Objects;
 
 public class Mergeable implements RestReadView<RevisionResource> {
   private static final Logger log = LoggerFactory.getLogger(Mergeable.class);
@@ -123,18 +122,22 @@ public class Mergeable implements RestReadView<RevisionResource> {
 
     Repository git = gitManager.openRepository(change.getProject());
     try {
-      Ref ref = git.getRef(change.getDest().get());
-      boolean refresh = force || isStale(change, ref);
-      if (!refresh && !otherBranches) {
+      ObjectId commit = toId(ps);
+      if (commit == null) {
+        result.mergeable = false;
         return result;
       }
+
+      Ref ref = git.getRef(change.getDest().get());
       ProjectState projectState = projectCache.get(change.getProject());
       String strategy = mergeUtilFactory.create(projectState)
           .mergeStrategyName();
+      Boolean old =
+          cache.getIfPresent(commit, ref, result.submitType, strategy);
 
-      if (refresh) {
-        result.mergeable =
-            refresh(change, ps, ref, result.submitType, strategy, git);
+      if (force || old == null) {
+        result.mergeable = refresh(change, ps, commit, ref, result.submitType,
+            strategy, git, old);
       }
 
       if (otherBranches) {
@@ -147,7 +150,8 @@ public class Mergeable implements RestReadView<RevisionResource> {
             if (other == null) {
               continue;
             }
-            if (isMergeable(change, ps, other, CHERRY_PICK, strategy, git)) {
+            if (cache.get(commit, other, SubmitType.CHERRY_PICK, strategy,
+                change.getDest(), git, db.get())) {
               result.mergeableInto.add(other.getName().substring(prefixLen));
             }
           }
@@ -159,23 +163,21 @@ public class Mergeable implements RestReadView<RevisionResource> {
     return result;
   }
 
-  private static boolean isStale(Change change, Ref ref) {
-    return change.getLastSha1MergeTested() == null
-        || !toRevId(ref).equals(change.getLastSha1MergeTested());
-  }
-
-  private static RevId toRevId(Ref ref) {
-    return new RevId(ref != null && ref.getObjectId() != null
-        ? ref.getObjectId().name()
-        : "");
+  private static ObjectId toId(PatchSet ps) {
+    try {
+      return ObjectId.fromString(ps.getRevision().get());
+    } catch (IllegalArgumentException e) {
+      log.error("Invalid revision on patch set " + ps);
+      return null;
+    }
   }
 
   private boolean refresh(final Change change, final PatchSet ps,
-      final Ref ref, SubmitType type, String strategy, Repository git)
-      throws OrmException, IOException {
-    final boolean mergeable = isMergeable(change, ps, ref, type, strategy, git);
-
-    Change c = db.get().changes().atomicUpdate(
+      ObjectId commit, final Ref ref, SubmitType type, String strategy,
+      Repository git, Boolean old) throws OrmException, IOException {
+    final boolean mergeable =
+        cache.get(commit, ref, type, strategy, change.getDest(), git, db.get());
+    db.get().changes().atomicUpdate(
         change.getId(),
         new AtomicUpdate<Change>() {
           @Override
@@ -183,29 +185,18 @@ public class Mergeable implements RestReadView<RevisionResource> {
             if (c.getStatus().isOpen()
                 && ps.getId().equals(c.currentPatchSetId())) {
               c.setMergeable(mergeable);
-              c.setLastSha1MergeTested(toRevId(ref));
+              ObjectId into = MergeabilityCache.toId(ref);
+              c.setLastSha1MergeTested(new RevId(
+                  !into.equals(ObjectId.zeroId()) ? into.name() : ""));
               return c;
             } else {
               return null;
             }
           }
         });
-    if (c != null) {
-      indexer.index(db.get(), c);
+    if (!Objects.equals(mergeable, old)) {
+      indexer.index(db.get(), change);
     }
     return mergeable;
   }
-
-  private boolean isMergeable(Change change, PatchSet ps, Ref ref,
-      SubmitType type, String strategy, Repository git) {
-    ObjectId commit;
-    try {
-      commit = ObjectId.fromString(ps.getRevision().get());
-    } catch (IllegalArgumentException e) {
-      log.error("Invalid revision on patch set " + ps);
-      return false;
-    }
-    return cache.get(
-        commit, ref, type, strategy, change.getDest(), git, db.get());
-  }
 }