SiteIndexer: Always scan changes from repo/db

This was changed to use ChangeCache in a2b7358d, with the intention of
binding ChangeCache to ScanningChangeCacheImpl in Reindex.
Unfortunately I forgot about the online reindexing case, where
ChangeCache is bound to SearchingChangeCacheImpl in a running master.
This had the effect of omitting from the list of changes to reindex
any changes that were not already present in the index. In many cases
this is fine, but if a change is missing for some reason (including a
race condition during creation), it would not be found.

Fix this by exposing the method in ScanningChangeCacheImpl to actually
scan a repo, and using that from both its Loader and SiteIndexer
directly.

Change-Id: Id384ff93abbb7b6c54819b6c2672fb1f45dc55bc

gerrit-server/src/main/java/com/google/gerrit/server/git/ScanningChangeCacheImpl.java

@@ -26,6 +26,7 @@ import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.cache.CacheModule;
 import com.google.gerrit.server.util.ManualRequestContext;
 import com.google.gerrit.server.util.OneOffRequestContext;
+import com.google.gwtorm.server.OrmException;
 import com.google.inject.Inject;
 import com.google.inject.Module;
 import com.google.inject.Singleton;
@@ -37,6 +38,7 @@ import org.eclipse.jgit.lib.Repository;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
+import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.LinkedHashSet;
@@ -95,29 +97,31 @@ public class ScanningChangeCacheImpl implements ChangeCache {
 
     @Override
     public List<Change> load(Project.NameKey key) throws Exception {
-      Repository repo = repoManager.openRepository(key);
-      try (ManualRequestContext ctx = requestContext.open()) {
-        ReviewDb db = ctx.getReviewDbProvider().get();
-        Map<String, Ref> refs =
-            repo.getRefDatabase().getRefs(RefNames.REFS_CHANGES);
-        Set<Change.Id> ids = new LinkedHashSet<>();
-        for (Ref r : refs.values()) {
-          Change.Id id = Change.Id.fromRef(r.getName());
-          if (id != null) {
-            ids.add(id);
-          }
-        }
-        List<Change> changes = new ArrayList<>(ids.size());
-         // A batch size of N may overload get(Iterable), so use something smaller,
-         // but still >1.
-        for (List<Change.Id> batch : Iterables.partition(ids, 30)) {
-          Iterables.addAll(changes, db.changes().get(batch));
-        }
-        return changes;
-      } finally {
-        repo.close();
+      try (Repository repo = repoManager.openRepository(key);
+          ManualRequestContext ctx = requestContext.open()) {
+        return scan(repo, ctx.getReviewDbProvider().get());
       }
     }
 
   }
+
+  public static List<Change> scan(Repository repo, ReviewDb db)
+      throws OrmException, IOException {
+    Map<String, Ref> refs =
+        repo.getRefDatabase().getRefs(RefNames.REFS_CHANGES);
+    Set<Change.Id> ids = new LinkedHashSet<>();
+    for (Ref r : refs.values()) {
+      Change.Id id = Change.Id.fromRef(r.getName());
+      if (id != null) {
+        ids.add(id);
+      }
+    }
+    List<Change> changes = new ArrayList<>(ids.size());
+    // A batch size of N may overload get(Iterable), so use something smaller,
+    // but still >1.
+    for (List<Change.Id> batch : Iterables.partition(ids, 30)) {
+      Iterables.addAll(changes, db.changes().get(batch));
+    }
+    return changes;
+  }
 }

gerrit-server/src/main/java/com/google/gerrit/server/index/SiteIndexer.java

@@ -33,11 +33,11 @@ import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.Project;
 import com.google.gerrit.reviewdb.server.ReviewDb;
 import com.google.gerrit.server.config.GerritServerConfig;
-import com.google.gerrit.server.git.ChangeCache;
 import com.google.gerrit.server.git.GitRepositoryManager;
 import com.google.gerrit.server.git.MergeUtil;
 import com.google.gerrit.server.git.MultiProgressMonitor;
 import com.google.gerrit.server.git.MultiProgressMonitor.Task;
+import com.google.gerrit.server.git.ScanningChangeCacheImpl;
 import com.google.gerrit.server.patch.PatchListLoader;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gwtorm.server.SchemaFactory;
@@ -112,7 +112,6 @@ public class SiteIndexer {
   }
 
   private final SchemaFactory<ReviewDb> schemaFactory;
-  private final ChangeCache changeCache;
   private final ChangeData.Factory changeDataFactory;
   private final GitRepositoryManager repoManager;
   private final ListeningExecutorService executor;
@@ -126,14 +125,12 @@ public class SiteIndexer {
 
   @Inject
   SiteIndexer(SchemaFactory<ReviewDb> schemaFactory,
-      ChangeCache changeCache,
       ChangeData.Factory changeDataFactory,
       GitRepositoryManager repoManager,
       @IndexExecutor(BATCH) ListeningExecutorService executor,
       ChangeIndexer.Factory indexerFactory,
       @GerritServerConfig Config config) {
     this.schemaFactory = schemaFactory;
-    this.changeCache = changeCache;
     this.changeDataFactory = changeDataFactory;
     this.repoManager = repoManager;
     this.executor = executor;
@@ -241,7 +238,7 @@ public class SiteIndexer {
           repo = repoManager.openRepository(project);
           Map<String, Ref> refs = repo.getRefDatabase().getRefs(ALL);
           db = schemaFactory.open();
-          for (Change c : changeCache.get(project)) {
+          for (Change c : ScanningChangeCacheImpl.scan(repo, db)) {
             Ref r = refs.get(c.currentPatchSetId().toRefName());
             if (r != null) {
               byId.put(r.getObjectId(), changeDataFactory.create(db, c));