Remove unnecessary fold in enrich policy name

server/src/main/java/org/elasticsearch/common/lucene/BytesRefs.java

@@ -23,8 +23,8 @@ public static String toString(Object value) {
         if (value == null) {
             return null;
         }
-        if (value instanceof BytesRef) {
-            return ((BytesRef) value).utf8ToString();
+        if (value instanceof BytesRef bytesRef) {
+            return bytesRef.utf8ToString();
         }
         return value.toString();
     }
@@ -36,8 +36,8 @@ public static BytesRef toBytesRef(Object value) {
         if (value == null) {
             return null;
         }
-        if (value instanceof BytesRef) {
-            return (BytesRef) value;
+        if (value instanceof BytesRef bytesRef) {
+            return bytesRef;
         }
         return new BytesRef(value.toString());
     }

x-pack/plugin/esql-core/src/main/java/org/elasticsearch/xpack/esql/core/expression/Foldables.java

@@ -6,6 +6,7 @@
  */
 package org.elasticsearch.xpack.esql.core.expression;
 
+import org.apache.lucene.util.BytesRef;
 import org.elasticsearch.xpack.esql.core.QlIllegalArgumentException;
 
 public abstract class Foldables {
@@ -16,4 +17,11 @@ public static Object valueOf(FoldContext ctx, Expression e) {
         }
         throw new QlIllegalArgumentException("Cannot determine value for {}", e);
     }
+
+    public static String stringLiteralValueOf(Expression expression, String message) {
+        if (expression instanceof Literal literal && literal.value() instanceof BytesRef bytesRef) {
+            return bytesRef.utf8ToString();
+        }
+        throw new QlIllegalArgumentException(message);
+    }
 }

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/enrich/EnrichPolicyResolver.java

@@ -59,6 +59,7 @@
 import java.util.Set;
 import java.util.stream.Collectors;
 
+import static org.elasticsearch.xpack.esql.core.expression.Foldables.stringLiteralValueOf;
 import static org.elasticsearch.xpack.esql.session.EsqlCCSUtils.markClusterWithFinalStateAndNoShards;
 
 /**
@@ -101,7 +102,9 @@ public EnrichPolicyResolver(
     }
 
     public record UnresolvedPolicy(String name, Enrich.Mode mode) {
-
+        public static UnresolvedPolicy from(Enrich e) {
+            return new UnresolvedPolicy(stringLiteralValueOf(e.policyName(), "Enrich policy must be a constant string"), e.mode());
+        }
     }
 
     /**

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/session/EsqlSession.java

@@ -15,7 +15,6 @@
 import org.elasticsearch.action.search.ShardSearchFailure;
 import org.elasticsearch.action.support.SubscribableListener;
 import org.elasticsearch.common.collect.Iterators;
-import org.elasticsearch.common.lucene.BytesRefs;
 import org.elasticsearch.compute.data.Block;
 import org.elasticsearch.compute.data.BlockUtils;
 import org.elasticsearch.compute.data.Page;
@@ -46,7 +45,6 @@
 import org.elasticsearch.xpack.esql.analysis.PreAnalyzer;
 import org.elasticsearch.xpack.esql.analysis.Verifier;
 import org.elasticsearch.xpack.esql.core.expression.Attribute;
-import org.elasticsearch.xpack.esql.core.expression.FoldContext;
 import org.elasticsearch.xpack.esql.core.expression.ReferenceAttribute;
 import org.elasticsearch.xpack.esql.core.tree.Source;
 import org.elasticsearch.xpack.esql.core.type.DataType;
@@ -88,6 +86,7 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import static java.util.stream.Collectors.toSet;
 import static org.elasticsearch.index.query.QueryBuilders.boolQuery;
 import static org.elasticsearch.xpack.esql.core.tree.Source.EMPTY;
 import static org.elasticsearch.xpack.esql.plan.logical.join.InlineJoin.firstSubPlan;
@@ -382,14 +381,7 @@ public void analyzedPlan(
         };
 
         PreAnalyzer.PreAnalysis preAnalysis = preAnalyzer.preAnalyze(parsed);
-        var unresolvedPolicies = preAnalysis.enriches.stream()
-            .map(
-                e -> new EnrichPolicyResolver.UnresolvedPolicy(
-                    BytesRefs.toString(e.policyName().fold(FoldContext.small() /* TODO remove me*/)),
-                    e.mode()
-                )
-            )
-            .collect(Collectors.toSet());
+        var unresolvedPolicies = preAnalysis.enriches.stream().map(EnrichPolicyResolver.UnresolvedPolicy::from).collect(toSet());
 
         EsqlCCSUtils.initCrossClusterState(indicesExpressionGrouper, verifier.licenseState(), preAnalysis.indices, executionInfo);
 
@@ -587,7 +579,7 @@ private IndexResolution checkSingleIndex(
     ) {
         // If all indices resolve to the same name, we can use that for BWC
         // Older clusters only can handle one name in LOOKUP JOIN
-        var localIndexNames = indexNames.stream().map(n -> RemoteClusterAware.splitIndexName(n)[1]).collect(Collectors.toSet());
+        var localIndexNames = indexNames.stream().map(n -> RemoteClusterAware.splitIndexName(n)[1]).collect(toSet());
         if (localIndexNames.size() == 1) {
             String indexName = localIndexNames.iterator().next();
             EsIndex newIndex = new EsIndex(index, lookupIndexResolution.get().mapping(), Map.of(indexName, IndexMode.LOOKUP));