Merge pull request #26270 from vespa-engine/arnej/ranking-expression-wrapping

Arnej/ranking expression wrapping

17 files changed, 253 insertions, 24 deletions

diff --git a/config-model/src/main/java/com/yahoo/schema/OnnxModel.java b/config-model/src/main/java/com/yahoo/schema/OnnxModel.java
index 6baaea6ea05..272b668b5fb 100644
--- a/config-model/src/main/java/com/yahoo/schema/OnnxModel.java
+++ b/config-model/src/main/java/com/yahoo/schema/OnnxModel.java
@@ -55,7 +55,7 @@ public class OnnxModel extends DistributableResource {
                 return ref.toString();
             }
             // or a function (evaluated by backend)
-            if (ref.isSimple() && "rankingExpression".equals(ref.name())) {
+            if (ref.isSimpleRankingExpressionWrapper()) {
                 var arg = ref.simpleArgument();
                 if (arg.isPresent()) {
                     return ref.toString();
diff --git a/config-model/src/main/java/com/yahoo/schema/RankProfile.java b/config-model/src/main/java/com/yahoo/schema/RankProfile.java
index 7cb0a088f5f..a00bbb682a8 100644
--- a/config-model/src/main/java/com/yahoo/schema/RankProfile.java
+++ b/config-model/src/main/java/com/yahoo/schema/RankProfile.java
@@ -1169,7 +1169,7 @@ public class RankProfile implements Cloneable {
             // Source is either a simple reference (query/attribute/constant/rankingExpression)...
             Optional<Reference> reference = Reference.simple(source);
             if (reference.isPresent()) {
-                if (reference.get().name().equals("rankingExpression") && reference.get().simpleArgument().isPresent()) {
+                if (reference.get().isSimpleRankingExpressionWrapper()) {
                     source = reference.get().simpleArgument().get();  // look up function below
                 } else {
                     return Optional.of(context.getType(reference.get()));
diff --git a/config-model/src/main/java/com/yahoo/schema/derived/RawRankProfile.java b/config-model/src/main/java/com/yahoo/schema/derived/RawRankProfile.java
index 31a38752bec..acb125197d2 100644
--- a/config-model/src/main/java/com/yahoo/schema/derived/RawRankProfile.java
+++ b/config-model/src/main/java/com/yahoo/schema/derived/RawRankProfile.java
@@ -20,6 +20,7 @@ import com.yahoo.searchlib.rankingexpression.parser.ParseException;
 import com.yahoo.searchlib.rankingexpression.rule.ReferenceNode;
 import com.yahoo.searchlib.rankingexpression.rule.SerializationContext;
 import com.yahoo.vespa.config.search.RankProfilesConfig;
+import static com.yahoo.searchlib.rankingexpression.Reference.wrapInRankingExpression;
 
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
@@ -273,9 +274,9 @@ public class RawRankProfile implements RankProfilesConfig.Producer {
                     String propertyName = RankingExpression.propertyName(referenceNode.getName());
                     String expressionString = function.getBody().getRoot().toString(context).toString();
                     context.addFunctionSerialization(propertyName, expressionString);
-                    ReferenceNode backendReferenceNode = new ReferenceNode("rankingExpression(" + referenceNode.getName() + ")",
-                                                                           referenceNode.getArguments().expressions(),
-                                                                           referenceNode.getOutput());
+                    var backendReferenceNode = new ReferenceNode(wrapInRankingExpression(referenceNode.getName()),
+                                                                 referenceNode.getArguments().expressions(),
+                                                                 referenceNode.getOutput());
                     // tell backend to map back to the name the user expects:
                     featureRenames.put(backendReferenceNode.toString(), referenceNode.toString());
                     functionFeatures.put(referenceNode.getName(), backendReferenceNode);
@@ -499,7 +500,7 @@ public class RawRankProfile implements RankProfilesConfig.Producer {
             if (expression.getRoot() instanceof ReferenceNode) {
                 properties.add(new Pair<>("vespa.rank." + phase, expression.getRoot().toString()));
             } else {
-                properties.add(new Pair<>("vespa.rank." + phase, "rankingExpression(" + name + ")"));
+                properties.add(new Pair<>("vespa.rank." + phase, wrapInRankingExpression(name)));
                 properties.add(new Pair<>(RankingExpression.propertyName(name), expression.getRoot().toString()));
             }
             return properties;
@@ -520,7 +521,7 @@ public class RawRankProfile implements RankProfilesConfig.Producer {
                 for (Map.Entry<String, String> mapping : onnxModel.getInputMap().entrySet()) {
                     String source = mapping.getValue();
                     if (functionNames.contains(source)) {
-                        onnxModel.addInputNameMapping(mapping.getKey(), "rankingExpression(" + source + ")");
+                        onnxModel.addInputNameMapping(mapping.getKey(), wrapInRankingExpression(source));
                     }
                 }
             }
diff --git a/config-model/src/test/derived/rankingmacros/rank-profiles.cfg b/config-model/src/test/derived/rankingmacros/rank-profiles.cfg
new file mode 100644
index 00000000000..71b7bc7166c
--- /dev/null
+++ b/config-model/src/test/derived/rankingmacros/rank-profiles.cfg
@@ -0,0 +1,83 @@
+rankprofile[].name "default"
+rankprofile[].name "unranked"
+rankprofile[].fef.property[].name "vespa.rank.firstphase"
+rankprofile[].fef.property[].value "value(0)"
+rankprofile[].fef.property[].name "vespa.hitcollector.heapsize"
+rankprofile[].fef.property[].value "0"
+rankprofile[].fef.property[].name "vespa.hitcollector.arraysize"
+rankprofile[].fef.property[].value "0"
+rankprofile[].fef.property[].name "vespa.dump.ignoredefaultfeatures"
+rankprofile[].fef.property[].value "true"
+rankprofile[].name "standalone"
+rankprofile[].fef.property[].name "rankingExpression(myfeature).rankingScript"
+rankprofile[].fef.property[].value "7 * attribute(num)"
+rankprofile[].fef.property[].name "rankingExpression(fourtimessum@2b1138e8965e7ff5.67f1e87166cfef86).rankingScript"
+rankprofile[].fef.property[].value "4 * (match + match)"
+rankprofile[].fef.property[].name "rankingExpression(macro_with_dollar$).rankingScript"
+rankprofile[].fef.property[].value "69"
+rankprofile[].fef.property[].name "rankingExpression(anotherfeature).rankingScript"
+rankprofile[].fef.property[].value "10 * rankingExpression(myfeature)"
+rankprofile[].fef.property[].name "rankingExpression(yetanotherfeature).rankingScript"
+rankprofile[].fef.property[].value "100 * rankingExpression(myfeature)"
+rankprofile[].fef.property[].name "rankingExpression(fourtimessum).rankingScript"
+rankprofile[].fef.property[].value "4 * (var1 + var2)"
+rankprofile[].fef.property[].name "vespa.rank.firstphase"
+rankprofile[].fef.property[].value "rankingExpression(firstphase)"
+rankprofile[].fef.property[].name "rankingExpression(firstphase).rankingScript"
+rankprofile[].fef.property[].value "match + fieldMatch(title) + rankingExpression(myfeature)"
+rankprofile[].fef.property[].name "vespa.rank.secondphase"
+rankprofile[].fef.property[].value "rankingExpression(secondphase)"
+rankprofile[].fef.property[].name "rankingExpression(secondphase).rankingScript"
+rankprofile[].fef.property[].value "rankingExpression(fourtimessum@2b1138e8965e7ff5.67f1e87166cfef86) + 0 * rankingExpression(macro_with_dollar$)"
+rankprofile[].fef.property[].name "vespa.summary.feature"
+rankprofile[].fef.property[].value "firstPhase"
+rankprofile[].fef.property[].name "vespa.summary.feature"
+rankprofile[].fef.property[].value "rankingExpression(myfeature)"
+rankprofile[].fef.property[].name "vespa.summary.feature"
+rankprofile[].fef.property[].value "rankingExpression(anotherfeature)"
+rankprofile[].fef.property[].name "vespa.summary.feature"
+rankprofile[].fef.property[].value "rankingExpression(yetanotherfeature)"
+rankprofile[].fef.property[].name "vespa.summary.feature"
+rankprofile[].fef.property[].value "rankingExpression(macro_with_dollar$)"
+rankprofile[].fef.property[].name "vespa.feature.rename"
+rankprofile[].fef.property[].value "rankingExpression(anotherfeature)"
+rankprofile[].fef.property[].name "vespa.feature.rename"
+rankprofile[].fef.property[].value "anotherfeature"
+rankprofile[].fef.property[].name "vespa.feature.rename"
+rankprofile[].fef.property[].value "rankingExpression(yetanotherfeature)"
+rankprofile[].fef.property[].name "vespa.feature.rename"
+rankprofile[].fef.property[].value "yetanotherfeature"
+rankprofile[].fef.property[].name "vespa.feature.rename"
+rankprofile[].fef.property[].value "rankingExpression(macro_with_dollar$)"
+rankprofile[].fef.property[].name "vespa.feature.rename"
+rankprofile[].fef.property[].value "macro_with_dollar$"
+rankprofile[].name "constantsAndMacro"
+rankprofile[].fef.property[].name "rankingExpression(c).rankingScript"
+rankprofile[].fef.property[].value "attribute(num)"
+rankprofile[].fef.property[].name "vespa.rank.firstphase"
+rankprofile[].fef.property[].value "rankingExpression(firstphase)"
+rankprofile[].fef.property[].name "rankingExpression(firstphase).rankingScript"
+rankprofile[].fef.property[].value "attribute(num) * 2.0 + 3.0"
+rankprofile[].fef.property[].name "vespa.summary.feature"
+rankprofile[].fef.property[].value "firstPhase"
+rankprofile[].name "doc"
+rankprofile[].fef.property[].name "rankingExpression(myfeature).rankingScript"
+rankprofile[].fef.property[].value "fieldMatch(title) + freshness(timestamp)"
+rankprofile[].fef.property[].name "rankingExpression(otherfeature@6b0a229a66fcaa04).rankingScript"
+rankprofile[].fef.property[].value "nativeRank(title,body)"
+rankprofile[].fef.property[].name "rankingExpression(otherfeature).rankingScript"
+rankprofile[].fef.property[].value "nativeRank(foo,body)"
+rankprofile[].fef.property[].name "vespa.rank.firstphase"
+rankprofile[].fef.property[].value "rankingExpression(firstphase)"
+rankprofile[].fef.property[].name "rankingExpression(firstphase).rankingScript"
+rankprofile[].fef.property[].value "rankingExpression(myfeature) * 10"
+rankprofile[].fef.property[].name "vespa.rank.secondphase"
+rankprofile[].fef.property[].value "rankingExpression(secondphase)"
+rankprofile[].fef.property[].name "rankingExpression(secondphase).rankingScript"
+rankprofile[].fef.property[].value "rankingExpression(otherfeature@6b0a229a66fcaa04) * rankingExpression(myfeature)"
+rankprofile[].fef.property[].name "vespa.summary.feature"
+rankprofile[].fef.property[].value "rankingExpression(myfeature)"
+rankprofile[].fef.property[].name "vespa.feature.rename"
+rankprofile[].fef.property[].value "rankingExpression(myfeature)"
+rankprofile[].fef.property[].name "vespa.feature.rename"
+rankprofile[].fef.property[].value "myfeature"
diff --git a/config-model/src/test/derived/rankingmacros/rankingmacros.sd b/config-model/src/test/derived/rankingmacros/rankingmacros.sd
new file mode 100644
index 00000000000..84598cb483a
--- /dev/null
+++ b/config-model/src/test/derived/rankingmacros/rankingmacros.sd
@@ -0,0 +1,105 @@
+# Copyright 2019 Oath Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+schema rankingmacros {
+
+  document rankingmacros {
+    field title type string {
+      indexing: index
+    }
+    field timestamp type long {
+      indexing: attribute
+    }
+    field description type string {
+      indexing: index
+    }
+    field num type int {
+      indexing: attribute
+    }
+    field abstract type string {
+      indexing: index
+    }
+    field body type string {
+      indexing: index
+    }
+    field usstaticrank type string {
+      indexing: attribute
+    }
+    field boostmax type string {
+      indexing: index
+    }
+    field entitytitle type string {
+      indexing: index
+    }
+  }
+
+  rank-profile standalone {
+    macro fourtimessum(var1, var2) {
+      expression: 4*(var1+var2)
+    }
+    macro myfeature() {
+       expression {
+         7 * attribute(num)
+       }
+    }
+    macro anotherfeature() {
+      expression: 10*myfeature
+    }
+    macro yetanotherfeature() {
+      expression: 100*rankingExpression(myfeature) # legacy form
+    }
+    macro macro_with_dollar$() { # Not allowed
+      expression: 69
+    }
+    first-phase {
+      expression: match + fieldMatch(title) + myfeature
+    }
+    second-phase {
+      expression: fourtimessum(match,match) + 0 * macro_with_dollar$
+    }
+    summary-features {
+      firstPhase
+      rankingExpression(myfeature)
+      anotherfeature
+      yetanotherfeature
+      macro_with_dollar$
+    }
+  }
+
+  # Profile with macro and constants
+  rank-profile constantsAndMacro {
+    macro c() {
+      expression: attribute(num)
+    }
+
+    constants {
+      a: 2
+      b: 3
+    }
+
+    first-phase {
+      expression: attribute(num) * a + b
+    }
+
+    summary-features {
+      firstPhase
+    }
+  }
+
+  # The example in the docs
+  rank-profile doc inherits default {
+    macro myfeature() {
+      expression: fieldMatch(title) + freshness(timestamp)
+    }
+    macro otherfeature(foo) {
+      expression{ nativeRank(foo, body) }
+    }
+
+    first-phase {
+      expression: myfeature * 10
+    }
+    second-phase {
+      expression: otherfeature(title) * myfeature
+    }
+    summary-features: myfeature
+  }
+
+}
diff --git a/config-model/src/test/java/com/yahoo/schema/derived/RankProfilesTestCase.java b/config-model/src/test/java/com/yahoo/schema/derived/RankProfilesTestCase.java
index 5c24b32e275..a4c03291ce2 100644
--- a/config-model/src/test/java/com/yahoo/schema/derived/RankProfilesTestCase.java
+++ b/config-model/src/test/java/com/yahoo/schema/derived/RankProfilesTestCase.java
@@ -17,4 +17,9 @@ public class RankProfilesTestCase extends AbstractExportingTestCase {
     void testRankProfiles() throws IOException, ParseException {
         assertCorrectDeriving("rankprofiles", null, new TestProperties(), new TestableDeployLogger());
     }
+
+    @Test
+    void testMacrosInRankProfiles() throws IOException, ParseException {
+        assertCorrectDeriving("rankingmacros", null, new TestProperties(), new TestableDeployLogger());
+    }
 }
diff --git a/container-search/src/main/java/com/yahoo/search/ranking/HitRescorer.java b/container-search/src/main/java/com/yahoo/search/ranking/HitRescorer.java
index ebdbbb693f1..cce6b42d323 100644
--- a/container-search/src/main/java/com/yahoo/search/ranking/HitRescorer.java
+++ b/container-search/src/main/java/com/yahoo/search/ranking/HitRescorer.java
@@ -3,6 +3,7 @@ package com.yahoo.search.ranking;
 
 import com.yahoo.search.result.FeatureData;
 import com.yahoo.search.result.Hit;
+import static com.yahoo.searchlib.rankingexpression.Reference.RANKING_EXPRESSION_WRAPPER;
 
 import java.util.function.Supplier;
 import java.util.logging.Logger;
@@ -42,7 +43,7 @@ class HitRescorer {
         }
     }
 
-    private static final String RE_PREFIX = "rankingExpression(";
+    private static final String RE_PREFIX = RANKING_EXPRESSION_WRAPPER + "(";
     private static final String RE_SUFFIX = ")";
     private static final int RE_PRE_LEN = RE_PREFIX.length();
     private static final int RE_SUF_LEN = RE_SUFFIX.length();
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 421f19475a6..7e9fa3f748a 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
@@ -11,6 +11,7 @@ import com.yahoo.io.GrowableByteBuffer;
 import com.yahoo.tensor.Tensor;
 import com.yahoo.tensor.serialization.JsonFormat;
 import com.yahoo.tensor.serialization.TypedBinaryFormat;
+import static com.yahoo.searchlib.rankingexpression.Reference.wrapInRankingExpression;
 
 import java.nio.charset.StandardCharsets;
 import java.util.Collections;
@@ -144,7 +145,7 @@ public class FeatureData implements Inspectable, JsonProducer {
         if (featureValue.valid()) return featureValue;
 
         // Try to wrap by rankingExpression(name)
-        return value.field("rankingExpression(" + featureName + ")");
+        return value.field(wrapInRankingExpression(featureName));
     }
 
     /** Returns the names of the features available in this */
diff --git a/model-evaluation/src/main/java/ai/vespa/models/evaluation/FunctionReference.java b/model-evaluation/src/main/java/ai/vespa/models/evaluation/FunctionReference.java
index 46134074137..34e34a3341d 100644
--- a/model-evaluation/src/main/java/ai/vespa/models/evaluation/FunctionReference.java
+++ b/model-evaluation/src/main/java/ai/vespa/models/evaluation/FunctionReference.java
@@ -2,6 +2,7 @@
 package ai.vespa.models.evaluation;
 
 import com.yahoo.collections.Pair;
+import static com.yahoo.searchlib.rankingexpression.Reference.wrapInRankingExpression;
 
 import java.util.Objects;
 import java.util.Optional;
@@ -51,7 +52,8 @@ class FunctionReference {
     }
 
     String serialForm() {
-        return "rankingExpression(" + name + (instance != null ? instance : "") + ")";
+        String extra = (instance != null ? instance : "");
+        return wrapInRankingExpression(name + extra);
     }
 
     @Override
diff --git a/model-evaluation/src/main/java/ai/vespa/models/evaluation/LazyArrayContext.java b/model-evaluation/src/main/java/ai/vespa/models/evaluation/LazyArrayContext.java
index 81325740218..47c246c008e 100644
--- a/model-evaluation/src/main/java/ai/vespa/models/evaluation/LazyArrayContext.java
+++ b/model-evaluation/src/main/java/ai/vespa/models/evaluation/LazyArrayContext.java
@@ -16,6 +16,7 @@ import com.yahoo.searchlib.rankingexpression.rule.ReferenceNode;
 import com.yahoo.stream.CustomCollectors;
 import com.yahoo.tensor.Tensor;
 import com.yahoo.tensor.TensorType;
+import static com.yahoo.searchlib.rankingexpression.Reference.RANKING_EXPRESSION_WRAPPER;
 
 import java.util.Arrays;
 import java.util.HashMap;
@@ -233,7 +234,11 @@ public final class LazyArrayContext extends Context implements ContextIndex {
                                         List<OnnxModel> onnxModels,
                                         Map<String, OnnxModel> onnxModelsInUse) {
             if (isFunctionReference(node)) {
-                FunctionReference reference = FunctionReference.fromSerial(node.toString()).get();
+                var opt = FunctionReference.fromSerial(node.toString());
+                if (opt.isEmpty()) {
+                    throw new IllegalArgumentException("Could not extract function " + node + " from serialized form '" + node.toString() +"'");
+                }
+                FunctionReference reference = opt.get();
                 bindTargets.add(reference.serialForm());
 
                 ExpressionFunction function = functions.get(reference);
@@ -313,7 +318,7 @@ public final class LazyArrayContext extends Context implements ContextIndex {
 
         private boolean isFunctionReference(ExpressionNode node) {
             if ( ! (node instanceof ReferenceNode reference)) return false;
-            return reference.getName().equals("rankingExpression") && reference.getArguments().size() == 1;
+            return reference.getName().equals(RANKING_EXPRESSION_WRAPPER) && reference.getArguments().size() == 1;
         }
 
         private boolean isOnnx(ExpressionNode node) {
diff --git a/model-evaluation/src/test/java/ai/vespa/models/evaluation/RankProfileImportingTest.java b/model-evaluation/src/test/java/ai/vespa/models/evaluation/RankProfileImportingTest.java
index 1a6f6925caf..c5084166c1f 100644
--- a/model-evaluation/src/test/java/ai/vespa/models/evaluation/RankProfileImportingTest.java
+++ b/model-evaluation/src/test/java/ai/vespa/models/evaluation/RankProfileImportingTest.java
@@ -49,4 +49,9 @@ public class RankProfileImportingTest {
         assertEquals("tensor()", rt.get().toString());
     }
 
+    @Test
+    public void testImportingExpressionsAsArguments() {
+        ModelTester tester = new ModelTester("src/test/resources/config/expressions-as-arguments/");
+        assertEquals(3, tester.models().size());
+    }
 }
diff --git a/searchlib/abi-spec.json b/searchlib/abi-spec.json
index 5413907e967..be0414421fe 100644
--- a/searchlib/abi-spec.json
+++ b/searchlib/abi-spec.json
@@ -364,6 +364,8 @@
       "public boolean equals(java.lang.Object)",
       "public int hashCode()",
       "public java.lang.String toString()",
+      "public static java.lang.String wrapInRankingExpression(java.lang.String)",
+      "public boolean isSimpleRankingExpressionWrapper()",
       "public java.lang.StringBuilder toString(java.lang.StringBuilder, com.yahoo.searchlib.rankingexpression.rule.SerializationContext, java.util.Deque, com.yahoo.searchlib.rankingexpression.rule.CompositeNode)",
       "public int compareTo(com.yahoo.searchlib.rankingexpression.Reference)",
       "public static com.yahoo.searchlib.rankingexpression.Reference fromIdentifier(java.lang.String)",
@@ -371,7 +373,9 @@
       "public static java.util.Optional simple(java.lang.String)",
       "public bridge synthetic int compareTo(java.lang.Object)"
     ],
-    "fields" : [ ]
+    "fields" : [
+      "public static final java.lang.String RANKING_EXPRESSION_WRAPPER"
+    ]
   },
   "com.yahoo.searchlib.rankingexpression.evaluation.AbstractArrayContext" : {
     "superClass" : "com.yahoo.searchlib.rankingexpression.evaluation.Context",
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/ExpressionFunction.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/ExpressionFunction.java
index 171151bfdf4..c7d69d7a36a 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/ExpressionFunction.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/ExpressionFunction.java
@@ -10,6 +10,7 @@ import com.yahoo.searchlib.rankingexpression.rule.ReferenceNode;
 import com.yahoo.searchlib.rankingexpression.rule.SerializationContext;
 import com.yahoo.tensor.TensorType;
 import com.yahoo.text.Utf8;
+import static com.yahoo.searchlib.rankingexpression.Reference.wrapInRankingExpression;
 
 import java.security.MessageDigest;
 import java.security.NoSuchAlgorithmException;
@@ -142,7 +143,7 @@ public class ExpressionFunction {
             if (shouldGenerateFeature(expr)) {
                 String funcName = "autogenerated_ranking_feature@" + Long.toHexString(symbolCode(key + "=" + binding));
                 context.addFunctionSerialization(RankingExpression.propertyName(funcName), binding);
-                binding = "rankingExpression(" + funcName + ")";
+                binding = wrapInRankingExpression(funcName);
             }
             argumentBindings.put(key, binding);
         }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/RankingExpression.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/RankingExpression.java
index c9f818544e3..c6de04ed755 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/RankingExpression.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/RankingExpression.java
@@ -11,6 +11,7 @@ import com.yahoo.searchlib.rankingexpression.rule.SerializationContext;
 import com.yahoo.tensor.TensorType;
 import com.yahoo.tensor.evaluation.TypeContext;
 import com.yahoo.text.Text;
+import static com.yahoo.searchlib.rankingexpression.Reference.RANKING_EXPRESSION_WRAPPER;
 
 import java.io.File;
 import java.io.FileNotFoundException;
@@ -80,7 +81,7 @@ public class RankingExpression implements Serializable {
 
     private String name = "";
     private ExpressionNode root;
-    private final static String RANKEXPRESSION = "rankingExpression(";
+    private final static String RANKEXPRESSION = RANKING_EXPRESSION_WRAPPER + "(";
     private final static String RANKINGSCRIPT = ").rankingScript";
     private final static String EXPRESSION_NAME = ").expressionName";
 
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/Reference.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/Reference.java
index eaecdf78162..64b251c0cd4 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/Reference.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/Reference.java
@@ -120,17 +120,30 @@ public class Reference extends Name implements Comparable<Reference> {
         return toString(new StringBuilder(), new SerializationContext(), null, null).toString();
     }
 
+    public static final String RANKING_EXPRESSION_WRAPPER = "rankingExpression";
+
+    public static String wrapInRankingExpression(String name) {
+        return RANKING_EXPRESSION_WRAPPER + "(" + name + ")";
+    }
+
+    public boolean isSimpleRankingExpressionWrapper() {
+        return name().equals(RANKING_EXPRESSION_WRAPPER) && isSimple();
+    }
+
     public StringBuilder toString(StringBuilder b, SerializationContext context, Deque<String> path, CompositeNode parent) {
         b.append(name());
         if (arguments.expressions().size() > 0) {
             b.append("(");
-            for (int i = 0; i < arguments.expressions().size(); i++) {
-                ExpressionNode e = arguments.expressions().get(i);
-                e.toString(b, context, path, parent);
-                if (i+1 < arguments.expressions().size()) {
-                    b.append(',');
+            if (isSimpleRankingExpressionWrapper()) {
+                b.append(simpleArgument().get());
+            } else {
+                for (int i = 0; i < arguments.expressions().size(); i++) {
+                    ExpressionNode e = arguments.expressions().get(i);
+                    e.toString(b, context, path, parent);
+                    if (i+1 < arguments.expressions().size()) {
+                        b.append(',');
+                    }
                 }
-
             }
             b.append(")");
         }
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ReferenceNode.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ReferenceNode.java
index 85a12a49958..ec377c6f5d9 100755
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ReferenceNode.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/ReferenceNode.java
@@ -8,6 +8,7 @@ import com.yahoo.searchlib.rankingexpression.evaluation.Context;
 import com.yahoo.searchlib.rankingexpression.evaluation.Value;
 import com.yahoo.tensor.TensorType;
 import com.yahoo.tensor.evaluation.TypeContext;
+import static com.yahoo.searchlib.rankingexpression.Reference.wrapInRankingExpression;
 
 import java.util.ArrayDeque;
 import java.util.Deque;
@@ -95,7 +96,7 @@ public final class ReferenceNode extends CompositeNode {
                     context.addFunctionTypeSerialization(functionName, function.returnType().get());
             }
             path.removeLast();
-            return string.append("rankingExpression(").append(functionName).append(')');
+            return string.append(wrapInRankingExpression(functionName));
         }
 
         // Not resolved in this context: output as-is
diff --git a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SerializationContext.java b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SerializationContext.java
index 7d0c0b98910..e2fffd824b9 100644
--- a/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SerializationContext.java
+++ b/searchlib/src/main/java/com/yahoo/searchlib/rankingexpression/rule/SerializationContext.java
@@ -6,6 +6,7 @@ import com.yahoo.searchlib.rankingexpression.RankingExpression;
 import com.yahoo.searchlib.rankingexpression.Reference;
 import com.yahoo.tensor.TensorType;
 import com.yahoo.tensor.evaluation.TypeContext;
+import static com.yahoo.searchlib.rankingexpression.Reference.wrapInRankingExpression;
 
 import java.util.Collection;
 import java.util.Collections;
@@ -97,13 +98,13 @@ public class SerializationContext extends FunctionReferenceContext {
 
     /** Adds the serialization of the argument type to a function */
     public void addArgumentTypeSerialization(String functionName, String argumentName, TensorType type) {
-        serializedFunctions.put("rankingExpression(" + functionName + ")." + argumentName + ".type", type.toString());
+        serializedFunctions.put(wrapInRankingExpression(functionName) + "." + argumentName + ".type", type.toString());
     }
 
     /** Adds the serialization of the return type of a function */
     public void addFunctionTypeSerialization(String functionName, TensorType type) {
         if (type.rank() == 0) return; // no explicit type implies scalar (aka rank 0 tensor)
-        serializedFunctions.put("rankingExpression(" + functionName + ").type", type.toString());
+        serializedFunctions.put(wrapInRankingExpression(functionName) + ".type", type.toString());
     }
 
     @Override