Render JSON results for the change table only using the index

Define a new type of field, STORED_ONLY, for storing arbitrary raw
bytes that cannot be searched. Add two fields of this type storing the
Change object and the list of SubmitRecord.Labels, which is exactly
the set of data needed to render a ChangeTable2. This avoids hitting
the database in the common case of rendering dashboards and search
results in the web UI, which may be costly on non-SQL implementations
Similarly we can avoid running and re-running the submit rule
evaluator.

This implementation has a minor bug in that changes to submit rules
may invalidate previously indexed labels, as can changing the set of
plugins with PredicateProviders.

There is substantial collateral damage to Reindex stemming from the
fact that indexing now depends on the submit rule evaluator, which in
turn requires pulling in plugins and hence a lot more Guice glue.

Change-Id: I3c10ed936eb9258e453c46f947abf35f5b8fb308

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

@@ -14,21 +14,35 @@
 
 package com.google.gerrit.server.index;
 
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Maps;
 import com.google.common.collect.Sets;
 import com.google.gerrit.reviewdb.client.Account;
+import com.google.gerrit.reviewdb.client.Change;
 import com.google.gerrit.reviewdb.client.ChangeMessage;
 import com.google.gerrit.reviewdb.client.PatchLineComment;
 import com.google.gerrit.reviewdb.client.PatchSet;
 import com.google.gerrit.reviewdb.client.PatchSetApproval;
+import com.google.gerrit.reviewdb.client.SubmitRecord;
 import com.google.gerrit.reviewdb.client.TrackingId;
 import com.google.gerrit.server.ChangeUtil;
+import com.google.gerrit.server.project.ChangeControl;
+import com.google.gerrit.server.project.NoSuchChangeException;
 import com.google.gerrit.server.query.change.ChangeData;
 import com.google.gerrit.server.query.change.ChangeQueryBuilder;
 import com.google.gerrit.server.query.change.ChangeStatusPredicate;
+import com.google.gwtorm.protobuf.CodecFactory;
+import com.google.gwtorm.protobuf.ProtobufCodec;
 import com.google.gwtorm.server.OrmException;
+import com.google.protobuf.CodedOutputStream;
 
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.sql.Timestamp;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
 import java.util.Set;
 
 /**
@@ -233,6 +247,82 @@ public class ChangeField {
         }
       };
 
+  public static class ChangeProtoField extends FieldDef.Single<ChangeData, byte[]> {
+    public static final ProtobufCodec<Change> CODEC =
+        CodecFactory.encoder(Change.class);
+
+    private ChangeProtoField() {
+      super("_change", FieldType.STORED_ONLY, true);
+    }
+
+    @Override
+    public byte[] get(ChangeData input, FieldDef.FillArgs args)
+        throws OrmException {
+      return CODEC.encodeToByteArray(input.change(args.db));
+    }
+  }
+
+  /** Serialized change object, used for pre-populating results. */
+  public static final ChangeProtoField CHANGE = new ChangeProtoField();
+
+  public static class SubmitLabelProtoField
+      extends FieldDef.Repeatable<ChangeData, byte[]> {
+    public static final ProtobufCodec<SubmitRecord.Label> CODEC =
+        CodecFactory.encoder(SubmitRecord.Label.class);
+
+    private SubmitLabelProtoField() {
+      super("_label", FieldType.STORED_ONLY, true);
+    }
+
+    @Override
+    public Iterable<byte[]> get(ChangeData input, FillArgs args)
+        throws OrmException {
+      // Flatten the highest-valued labels to mimic the results from ChangeJson
+      // with standard labels.
+      Map<String, SubmitRecord.Label> labels = Maps.newLinkedHashMap();
+      for (SubmitRecord rec : getSubmitRecords(input, args)) {
+        if (rec.labels == null) {
+          continue;
+        }
+        for (SubmitRecord.Label r : rec.labels) {
+          SubmitRecord.Label p = labels.get(r.label);
+          if (p == null || p.status.compareTo(r.status) < 0) {
+            labels.put(r.label, r);
+          }
+        }
+      }
+      return toProtos(CODEC, labels.values());
+    }
+
+    private List<SubmitRecord> getSubmitRecords(ChangeData input,
+        FillArgs args) throws OrmException {
+      ChangeControl ctl;
+      try {
+        // Use the ChangeControl for InternalUser. This will give bogus
+        // results for whether or not the change is submittable, but does
+        // not affect label calculation.
+        ctl = args.changeControlFor(input.change(args.db));
+      } catch (NoSuchChangeException e) {
+        throw new OrmException(e);
+      }
+      if (ctl == null) {
+        return ImmutableList.of();
+      }
+      PatchSet ps = input.currentPatchSet(args.db);
+      if (ps == null) {
+        return ImmutableList.of();
+      }
+      return ctl.canSubmit(args.db.get(), ps, input, true, true, true);
+    }
+  }
+
+  /**
+   * Serialized labels from the submit rule evaluator, used for pre-populating
+   * results.
+   */
+  public static final SubmitLabelProtoField SUBMIT_RECORD_LABEL =
+      new SubmitLabelProtoField();
+
   public static String formatLabel(String label, int value) {
     return formatLabel(label, value, null);
   }
@@ -273,4 +363,22 @@ public class ChangeField {
           return r;
         }
       };
+
+  private static <T> List<byte[]> toProtos(ProtobufCodec<T> codec, Collection<T> objs)
+      throws OrmException {
+    List<byte[]> result = Lists.newArrayListWithCapacity(objs.size());
+    ByteArrayOutputStream out = new ByteArrayOutputStream(256);
+    try {
+      for (T obj : objs) {
+        out.reset();
+        CodedOutputStream cos = CodedOutputStream.newInstance(out);
+        codec.encode(obj, cos);
+        cos.flush();
+        result.add(out.toByteArray());
+      }
+    } catch (IOException e) {
+      throw new OrmException(e);
+    }
+    return result;
+  }
 }