diff --git a/src/main/java/com/google/gerrit/elasticsearch/AbstractElasticIndex.java b/src/main/java/com/google/gerrit/elasticsearch/AbstractElasticIndex.java
index 908d9a7..d4f2c5d 100644
--- a/src/main/java/com/google/gerrit/elasticsearch/AbstractElasticIndex.java
+++ b/src/main/java/com/google/gerrit/elasticsearch/AbstractElasticIndex.java
@@ -30,7 +30,7 @@
 import com.google.common.io.BaseEncoding;
 import com.google.common.io.CharStreams;
 import com.google.gerrit.common.Nullable;
-import com.google.gerrit.elasticsearch.ElasticMapping.MappingProperties;
+import com.google.gerrit.elasticsearch.ElasticMapping.Mapping;
 import com.google.gerrit.elasticsearch.builders.QueryBuilder;
 import com.google.gerrit.elasticsearch.builders.SearchSourceBuilder;
 import com.google.gerrit.elasticsearch.bulk.DeleteRequest;
@@ -226,14 +226,14 @@
 
   protected abstract String getId(V v);
 
-  protected String getMappingsForSingleType(MappingProperties properties) {
-    return getMappingsFor(properties);
+  protected String getMappingsForSingleType(Mapping mapping) {
+    return getMappingsFor(mapping);
   }
 
-  protected String getMappingsFor(MappingProperties properties) {
+  protected String getMappingsFor(Mapping mapping) {
     JsonObject mappings = new JsonObject();
 
-    mappings.add(MAPPINGS, gson.toJsonTree(properties));
+    mappings.add(MAPPINGS, gson.toJsonTree(mapping));
     return gson.toJson(mappings);
   }
 
diff --git a/src/main/java/com/google/gerrit/elasticsearch/ElasticAccountIndex.java b/src/main/java/com/google/gerrit/elasticsearch/ElasticAccountIndex.java
index 1da80ae..1e94148 100644
--- a/src/main/java/com/google/gerrit/elasticsearch/ElasticAccountIndex.java
+++ b/src/main/java/com/google/gerrit/elasticsearch/ElasticAccountIndex.java
@@ -15,7 +15,7 @@
 package com.google.gerrit.elasticsearch;
 
 import com.google.common.collect.ImmutableSet;
-import com.google.gerrit.elasticsearch.ElasticMapping.MappingProperties;
+import com.google.gerrit.elasticsearch.ElasticMapping.Mapping;
 import com.google.gerrit.elasticsearch.bulk.BulkRequest;
 import com.google.gerrit.elasticsearch.bulk.IndexRequest;
 import com.google.gerrit.elasticsearch.bulk.UpdateRequest;
@@ -46,7 +46,7 @@
 public class ElasticAccountIndex extends AbstractElasticIndex<Account.Id, AccountState>
     implements AccountIndex {
   static class AccountMapping {
-    final MappingProperties accounts;
+    final Mapping accounts;
 
     AccountMapping(Schema<AccountState> schema, ElasticQueryAdapter adapter) {
       this.accounts = ElasticMapping.createMapping(schema, adapter);
diff --git a/src/main/java/com/google/gerrit/elasticsearch/ElasticChangeIndex.java b/src/main/java/com/google/gerrit/elasticsearch/ElasticChangeIndex.java
index a4674bf..8504e16 100644
--- a/src/main/java/com/google/gerrit/elasticsearch/ElasticChangeIndex.java
+++ b/src/main/java/com/google/gerrit/elasticsearch/ElasticChangeIndex.java
@@ -17,7 +17,7 @@
 import static java.util.Objects.requireNonNull;
 
 import com.google.common.collect.ImmutableSet;
-import com.google.gerrit.elasticsearch.ElasticMapping.MappingProperties;
+import com.google.gerrit.elasticsearch.ElasticMapping.Mapping;
 import com.google.gerrit.elasticsearch.bulk.BulkRequest;
 import com.google.gerrit.elasticsearch.bulk.IndexRequest;
 import com.google.gerrit.elasticsearch.bulk.UpdateRequest;
@@ -53,12 +53,12 @@
 class ElasticChangeIndex extends AbstractElasticIndex<Change.Id, ChangeData>
     implements ChangeIndex {
   static class ChangeMapping {
-    final MappingProperties changes;
-    final MappingProperties openChanges;
-    final MappingProperties closedChanges;
+    final Mapping changes;
+    final Mapping openChanges;
+    final Mapping closedChanges;
 
     ChangeMapping(Schema<ChangeData> schema, ElasticQueryAdapter adapter) {
-      MappingProperties mapping = ElasticMapping.createMapping(schema, adapter);
+      Mapping mapping = ElasticMapping.createMapping(schema, adapter);
       this.changes = mapping;
       this.openChanges = mapping;
       this.closedChanges = mapping;
diff --git a/src/main/java/com/google/gerrit/elasticsearch/ElasticGroupIndex.java b/src/main/java/com/google/gerrit/elasticsearch/ElasticGroupIndex.java
index 626203a..e0b337e 100644
--- a/src/main/java/com/google/gerrit/elasticsearch/ElasticGroupIndex.java
+++ b/src/main/java/com/google/gerrit/elasticsearch/ElasticGroupIndex.java
@@ -15,7 +15,7 @@
 package com.google.gerrit.elasticsearch;
 
 import com.google.common.collect.ImmutableSet;
-import com.google.gerrit.elasticsearch.ElasticMapping.MappingProperties;
+import com.google.gerrit.elasticsearch.ElasticMapping.Mapping;
 import com.google.gerrit.elasticsearch.bulk.BulkRequest;
 import com.google.gerrit.elasticsearch.bulk.IndexRequest;
 import com.google.gerrit.elasticsearch.bulk.UpdateRequest;
@@ -46,7 +46,7 @@
 public class ElasticGroupIndex extends AbstractElasticIndex<AccountGroup.UUID, InternalGroup>
     implements GroupIndex {
   static class GroupMapping {
-    final MappingProperties groups;
+    final Mapping groups;
 
     GroupMapping(Schema<InternalGroup> schema, ElasticQueryAdapter adapter) {
       this.groups = ElasticMapping.createMapping(schema, adapter);
diff --git a/src/main/java/com/google/gerrit/elasticsearch/ElasticMapping.java b/src/main/java/com/google/gerrit/elasticsearch/ElasticMapping.java
index 6bae325..1668450 100644
--- a/src/main/java/com/google/gerrit/elasticsearch/ElasticMapping.java
+++ b/src/main/java/com/google/gerrit/elasticsearch/ElasticMapping.java
@@ -18,6 +18,7 @@
 import com.google.gerrit.index.FieldDef;
 import com.google.gerrit.index.FieldType;
 import com.google.gerrit.index.Schema;
+import com.google.gson.annotations.SerializedName;
 import java.util.Map;
 
 class ElasticMapping {
@@ -25,7 +26,7 @@
   protected static final String TIMESTAMP_FIELD_TYPE = "date";
   protected static final String TIMESTAMP_FIELD_FORMAT = "date_optional_time";
 
-  static MappingProperties createMapping(Schema<?> schema, ElasticQueryAdapter adapter) {
+  static Mapping createMapping(Schema<?> schema, ElasticQueryAdapter adapter) {
     ElasticMapping.Builder mapping = new ElasticMapping.Builder(adapter);
     for (FieldDef<?, ?> field : schema.getFields().values()) {
       String name = field.getName();
@@ -46,6 +47,11 @@
         throw new IllegalStateException("Unsupported field type: " + fieldType.getName());
       }
     }
+    mapping.addSourceIncludes(
+        schema.getFields().values().stream()
+            .filter(f -> f.isStored())
+            .map(f -> f.getName())
+            .toArray(String[]::new));
     return mapping.build();
   }
 
@@ -53,15 +59,18 @@
     private final ElasticQueryAdapter adapter;
     private final ImmutableMap.Builder<String, FieldProperties> fields =
         new ImmutableMap.Builder<>();
+    private final ImmutableMap.Builder<String, String[]> sourceIncludes =
+        new ImmutableMap.Builder<>();
 
     Builder(ElasticQueryAdapter adapter) {
       this.adapter = adapter;
     }
 
-    MappingProperties build() {
-      MappingProperties properties = new MappingProperties();
-      properties.properties = fields.build();
-      return properties;
+    Mapping build() {
+      Mapping mapping = new Mapping();
+      mapping.properties = fields.build();
+      mapping.source = sourceIncludes.build();
+      return mapping;
     }
 
     Builder addExactField(String name) {
@@ -99,13 +108,21 @@
       return this;
     }
 
+    Builder addSourceIncludes(String[] includes) {
+      sourceIncludes.put("includes", includes);
+      return this;
+    }
+
     Builder add(String name, String type) {
       fields.put(name, new FieldProperties(type));
       return this;
     }
   }
 
-  static class MappingProperties {
+  static class Mapping {
+    @SerializedName("_source")
+    Map<String, String[]> source;
+
     Map<String, FieldProperties> properties;
   }
 
diff --git a/src/main/java/com/google/gerrit/elasticsearch/ElasticProjectIndex.java b/src/main/java/com/google/gerrit/elasticsearch/ElasticProjectIndex.java
index 99b202d..4703f1f 100644
--- a/src/main/java/com/google/gerrit/elasticsearch/ElasticProjectIndex.java
+++ b/src/main/java/com/google/gerrit/elasticsearch/ElasticProjectIndex.java
@@ -15,7 +15,7 @@
 package com.google.gerrit.elasticsearch;
 
 import com.google.common.collect.ImmutableSet;
-import com.google.gerrit.elasticsearch.ElasticMapping.MappingProperties;
+import com.google.gerrit.elasticsearch.ElasticMapping.Mapping;
 import com.google.gerrit.elasticsearch.bulk.BulkRequest;
 import com.google.gerrit.elasticsearch.bulk.IndexRequest;
 import com.google.gerrit.elasticsearch.bulk.UpdateRequest;
@@ -48,7 +48,7 @@
 public class ElasticProjectIndex extends AbstractElasticIndex<Project.NameKey, ProjectData>
     implements ProjectIndex {
   static class ProjectMapping {
-    MappingProperties projects;
+    Mapping projects;
 
     ProjectMapping(Schema<ProjectData> schema, ElasticQueryAdapter adapter) {
       this.projects = ElasticMapping.createMapping(schema, adapter);