Always return metadata in get/search APIs.

core/src/main/java/org/elasticsearch/index/engine/Engine.java

@@ -995,7 +995,6 @@ public long endTime() {
     public static class Get {
         private final boolean realtime;
         private final Term uid;
-        private boolean loadSource = true;
         private long version = Versions.MATCH_ANY;
         private VersionType versionType = VersionType.INTERNAL;
 
@@ -1012,15 +1011,6 @@ public Term uid() {
             return uid;
         }
 
-        public boolean loadSource() {
-            return this.loadSource;
-        }
-
-        public Get loadSource(boolean loadSource) {
-            this.loadSource = loadSource;
-            return this;
-        }
-
         public long version() {
             return version;
         }

core/src/main/java/org/elasticsearch/index/engine/InternalEngine.java

@@ -305,9 +305,6 @@ public GetResult get(Get get) throws EngineException {
                         Uid uid = Uid.createUid(get.uid().text());
                         throw new VersionConflictEngineException(shardId, uid.type(), uid.id(), versionValue.version(), get.version());
                     }
-                    if (!get.loadSource()) {
-                        return new GetResult(true, versionValue.version(), null);
-                    }
                     Translog.Operation op = translog.read(versionValue.translogLocation());
                     if (op != null) {
                         return new GetResult(true, versionValue.version(), op.getSource());

core/src/main/java/org/elasticsearch/index/fieldvisitor/AllFieldsVisitor.java

@@ -27,6 +27,7 @@
 public class AllFieldsVisitor extends FieldsVisitor {
 
     public AllFieldsVisitor() {
+        super(true);
     }
 
     @Override

core/src/main/java/org/elasticsearch/index/fieldvisitor/CustomFieldsVisitor.java

@@ -19,8 +19,6 @@
 package org.elasticsearch.index.fieldvisitor;
 
 import org.apache.lucene.index.FieldInfo;
-import org.elasticsearch.index.mapper.internal.SourceFieldMapper;
-import org.elasticsearch.index.mapper.internal.UidFieldMapper;
 
 import java.io.IOException;
 import java.util.Set;
@@ -32,21 +30,16 @@
  */
 public class CustomFieldsVisitor extends FieldsVisitor {
 
-    private final boolean loadSource;
     private final Set<String> fields;
 
     public CustomFieldsVisitor(Set<String> fields, boolean loadSource) {
-        this.loadSource = loadSource;
+        super(loadSource);
         this.fields = fields;
     }
 
     @Override
     public Status needsField(FieldInfo fieldInfo) throws IOException {
-
-        if (loadSource && SourceFieldMapper.NAME.equals(fieldInfo.name)) {
-            return Status.YES;
-        }
-        if (UidFieldMapper.NAME.equals(fieldInfo.name)) {
+        if (super.needsField(fieldInfo) == Status.YES) {
             return Status.YES;
         }
 

core/src/main/java/org/elasticsearch/index/fieldvisitor/FieldsVisitor.java

@@ -19,6 +19,7 @@
 package org.elasticsearch.index.fieldvisitor;
 
 import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableSet;
 
 import org.apache.lucene.index.FieldInfo;
 import org.apache.lucene.index.StoredFieldVisitor;
@@ -27,30 +28,63 @@
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.index.mapper.DocumentMapper;
 import org.elasticsearch.index.mapper.FieldMapper;
-import org.elasticsearch.index.mapper.FieldMappers;
 import org.elasticsearch.index.mapper.MappedFieldType;
 import org.elasticsearch.index.mapper.MapperService;
 import org.elasticsearch.index.mapper.Uid;
+import org.elasticsearch.index.mapper.internal.ParentFieldMapper;
+import org.elasticsearch.index.mapper.internal.RoutingFieldMapper;
 import org.elasticsearch.index.mapper.internal.SourceFieldMapper;
+import org.elasticsearch.index.mapper.internal.TTLFieldMapper;
+import org.elasticsearch.index.mapper.internal.TimestampFieldMapper;
 import org.elasticsearch.index.mapper.internal.UidFieldMapper;
 
 import java.io.IOException;
-import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
+import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
 
 import static com.google.common.collect.Maps.newHashMap;
 
 /**
+ * Base {@link StoredFieldsVisitor} that retrieves all non-redundant metadata.
  */
-public abstract class FieldsVisitor extends StoredFieldVisitor {
-
+public class FieldsVisitor extends StoredFieldVisitor {
+
+    private static final Set<String> BASE_REQUIRED_FIELDS = ImmutableSet.of(
+            UidFieldMapper.NAME,
+            TimestampFieldMapper.NAME,
+            TTLFieldMapper.NAME,
+            RoutingFieldMapper.NAME,
+            ParentFieldMapper.NAME
+   );
+
+    private final boolean loadSource;
+    private final Set<String> requiredFields;
     protected BytesReference source;
     protected Uid uid;
     protected Map<String, List<Object>> fieldsValues;
 
+    public FieldsVisitor(boolean loadSource) {
+        this.loadSource = loadSource;
+        requiredFields = new HashSet<>();
+        reset();
+    }
+
+    @Override
+    public Status needsField(FieldInfo fieldInfo) throws IOException {
+        if (requiredFields.remove(fieldInfo.name)) {
+            return Status.YES;
+        }
+        // All these fields are single-valued so we can stop when the set is
+        // empty
+        return requiredFields.isEmpty()
+                ? Status.STOP
+                : Status.NO;
+    }
+
     public void postProcess(MapperService mapperService) {
         if (uid != null) {
             DocumentMapper documentMapper = mapperService.documentMapper(uid.type());
@@ -133,6 +167,18 @@ public Uid uid() {
         return uid;
     }
 
+    public String routing() {
+        if (fieldsValues == null) {
+            return null;
+        }
+        List<Object> values = fieldsValues.get(RoutingFieldMapper.NAME);
+        if (values == null || values.isEmpty()) {
+            return null;
+        }
+        assert values.size() == 1;
+        return values.get(0).toString();
+    }
+
     public Map<String, List<Object>> fields() {
         return fieldsValues != null
                 ? fieldsValues
@@ -143,6 +189,11 @@ public void reset() {
         if (fieldsValues != null) fieldsValues.clear();
         source = null;
         uid = null;
+
+        requiredFields.addAll(BASE_REQUIRED_FIELDS);
+        if (loadSource) {
+            requiredFields.add(SourceFieldMapper.NAME);
+        }
     }
 
     void addValue(String name, Object value) {

core/src/main/java/org/elasticsearch/index/fieldvisitor/JustUidFieldsVisitor.java

@@ -27,6 +27,10 @@
  */
 public class JustUidFieldsVisitor extends FieldsVisitor {
 
+    public JustUidFieldsVisitor() {
+        super(false);
+    }
+
     @Override
     public Status needsField(FieldInfo fieldInfo) throws IOException {
         if (UidFieldMapper.NAME.equals(fieldInfo.name)) {

core/src/main/java/org/elasticsearch/index/fieldvisitor/SingleFieldsVisitor.java

@@ -35,6 +35,7 @@ public class SingleFieldsVisitor extends FieldsVisitor {
     private String field;
 
     public SingleFieldsVisitor(String field) {
+        super(false);
         this.field = field;
     }