From d6ab2fd110f0f2b3133f2a552ffb991eac522f74 Mon Sep 17 00:00:00 2001
From: Andrea Boriero <andrea@hibernate.org>
Date: Tue, 27 Aug 2024 10:58:40 +0200
Subject: [PATCH] HHH-18511 ArrayIndexOutOfBoundsException in
 ImmutableFetchList

---
 .../internal/CompoundNaturalIdMapping.java      | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/CompoundNaturalIdMapping.java b/hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/CompoundNaturalIdMapping.java
index 37c931e949..0e942286af 100644
--- a/hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/CompoundNaturalIdMapping.java
+++ b/hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/CompoundNaturalIdMapping.java
@@ -61,6 +61,11 @@ public class CompoundNaturalIdMapping extends AbstractNaturalIdMapping implement
 	private final List<SingularAttributeMapping> attributes;
 
 	private List<JdbcMapping> jdbcMappings;
+	/*
+		This value is used to determine the size of the array used to create the ImmutableFetchList (see org.hibernate.sql.results.graph.internal.ImmutableFetchList#Builder)
+		The Fetch is inserted into the array at a position corresponding to its Fetchable key value.
+	 */
+	private final int maxFetchableKeyIndex;
 
 	public CompoundNaturalIdMapping(
 			EntityMappingType declaringType,
@@ -69,6 +74,14 @@ public class CompoundNaturalIdMapping extends AbstractNaturalIdMapping implement
 		super( declaringType, isMutable( attributes ) );
 		this.attributes = attributes;
 
+		int maxIndex = 0;
+		for ( SingularAttributeMapping attribute : attributes ) {
+			if ( attribute.getFetchableKey() > maxIndex ) {
+				maxIndex = attribute.getFetchableKey();
+			}
+		}
+		this.maxFetchableKeyIndex = maxIndex + 1;
+
 		creationProcess.registerInitializationCallback(
 				"Determine compound natural-id JDBC mappings ( " + declaringType.getEntityName() + ")",
 				() -> {
@@ -531,6 +544,10 @@ public class CompoundNaturalIdMapping extends AbstractNaturalIdMapping implement
 		attributes.forEach( consumer );
 	}
 
+	@Override
+	public int getNumberOfFetchableKeys() {
+		return maxFetchableKeyIndex;
+	}
 
 	public static class DomainResultImpl implements DomainResult<Object[]>, FetchParent {
 		private final NavigablePath navigablePath;