1 files changed, 23 insertions, 8 deletions
diff --git a/container-search/src/main/java/com/yahoo/search/result/FeatureData.java b/container-search/src/main/java/com/yahoo/search/result/FeatureData.java
index 7e5d6b12f30..1fd8f6e7e17 100644
--- a/container-search/src/main/java/com/yahoo/search/result/FeatureData.java
+++ b/container-search/src/main/java/com/yahoo/search/result/FeatureData.java
@@ -18,7 +18,7 @@ import java.util.Set;
 
 /**
  * A wrapper for structured data representing feature values: A map of floats and tensors.
- * This class is not thread safe even when it is only consumed.
+ * This class is immutable but not thread safe.
  */
 public class FeatureData implements Inspectable, JsonProducer {
 
@@ -26,6 +26,8 @@ public class FeatureData implements Inspectable, JsonProducer {
 
     private Set<String> featureNames = null;
 
+    private String jsonForm = null;
+
     public FeatureData(Inspector value) {
         this.value = value;
     }
@@ -39,14 +41,11 @@ public class FeatureData implements Inspectable, JsonProducer {
     public Inspector inspect() { return value; }
 
     @Override
-    public String toString() {
-        if (value.type() == Type.EMPTY) return "";
-        return toJson();
-    }
-
-    @Override
     public String toJson() {
-        return writeJson(new StringBuilder()).toString();
+        if (jsonForm != null) return jsonForm;
+
+        jsonForm = writeJson(new StringBuilder()).toString();
+        return jsonForm;
     }
 
     @Override
@@ -95,6 +94,22 @@ public class FeatureData implements Inspectable, JsonProducer {
         return featureNames;
     }
 
+    @Override
+    public String toString() {
+        if (value.type() == Type.EMPTY) return "";
+        return toJson();
+    }
+
+    @Override
+    public int hashCode() { return toJson().hashCode(); }
+
+    @Override
+    public boolean equals(Object other) {
+        if (other == this) return true;
+        if ( ! (other instanceof FeatureData)) return false;
+        return ((FeatureData)other).toJson().equals(this.toJson());
+    }
+
     /** A JSON encoder which encodes DATA as a tensor */
     private static class Encoder extends JsonRender.StringEncoder {