From 41111b06cd7fed7a0271e5a649692e7061bf46bd Mon Sep 17 00:00:00 2001
From: Sanne Grinovero <sanne@hibernate.org>
Date: Wed, 30 Jul 2025 14:10:08 +0100
Subject: [PATCH] HHH-19668 Reduce size of collections held in
 ParameterInterpretationImpl before storing them in the cache
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Instances of ParameterInterpretationImpl are being held in the interpretation cache for native queries. We had reports of these elements having a substantial impact on memory consumption.

A simple improvement is to ensure the collections being held on by the container object are minimized; some more substantial improvements could also be investigated but I’ll leave those for another time.
---
 .../internal/util/collections/CollectionHelper.java       | 6 ++++++
 .../org/hibernate/query/sql/internal/NativeQueryImpl.java | 8 +++++---
 .../query/sql/internal/ParameterRecognizerImpl.java       | 5 ++---
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/hibernate-core/src/main/java/org/hibernate/internal/util/collections/CollectionHelper.java b/hibernate-core/src/main/java/org/hibernate/internal/util/collections/CollectionHelper.java
index a6486608c77b..f1dea4a5e78d 100644
--- a/hibernate-core/src/main/java/org/hibernate/internal/util/collections/CollectionHelper.java
+++ b/hibernate-core/src/main/java/org/hibernate/internal/util/collections/CollectionHelper.java
@@ -343,6 +343,9 @@ public static <T> Set<T> toSmallSet(Set<T> set) {
 	 * The goal is to save memory.
 	 */
 	public static <K, V> Map<K, V> toSmallMap(final Map<K, V> map) {
+		if ( map == null ) {
+			return emptyMap();
+		}
 		return switch ( map.size() ) {
 			case 0 -> emptyMap();
 			case 1 -> {
@@ -363,6 +366,9 @@ public static <K, V> Map<K, V> toSmallMap(final Map<K, V> map) {
 	 * The goal is to save memory.
 	 */
 	public static <V> List<V> toSmallList(ArrayList<V> arrayList) {
+		if ( arrayList == null ) {
+			return emptyList();
+		}
 		return switch ( arrayList.size() ) {
 			case 0 -> emptyList();
 			case 1 -> singletonList( arrayList.get( 0 ) );
diff --git a/hibernate-core/src/main/java/org/hibernate/query/sql/internal/NativeQueryImpl.java b/hibernate-core/src/main/java/org/hibernate/query/sql/internal/NativeQueryImpl.java
index 1af5735720e7..1ce0bbdd8bab 100644
--- a/hibernate-core/src/main/java/org/hibernate/query/sql/internal/NativeQueryImpl.java
+++ b/hibernate-core/src/main/java/org/hibernate/query/sql/internal/NativeQueryImpl.java
@@ -128,6 +128,8 @@
 import static org.hibernate.internal.util.collections.CollectionHelper.isEmpty;
 import static org.hibernate.internal.util.collections.CollectionHelper.isNotEmpty;
 import static org.hibernate.internal.util.collections.CollectionHelper.makeCopy;
+import static org.hibernate.internal.util.collections.CollectionHelper.toSmallList;
+import static org.hibernate.internal.util.collections.CollectionHelper.toSmallMap;
 import static org.hibernate.internal.util.type.PrimitiveWrapperHelper.getDescriptorByPrimitiveType;
 import static org.hibernate.jpa.HibernateHints.HINT_NATIVE_LOCK_MODE;
 import static org.hibernate.query.results.internal.Builders.resultClassBuilder;
@@ -1742,9 +1744,9 @@ private static class ParameterInterpretationImpl implements ParameterInterpretat
 
 		public ParameterInterpretationImpl(ParameterRecognizerImpl parameterRecognizer) {
 			this.sqlString = parameterRecognizer.getAdjustedSqlString();
-			this.parameterList = parameterRecognizer.getParameterList();
-			this.positionalParameters = parameterRecognizer.getPositionalQueryParameters();
-			this.namedParameters = parameterRecognizer.getNamedQueryParameters();
+			this.parameterList = toSmallList( parameterRecognizer.getParameterList() );
+			this.positionalParameters = toSmallMap( parameterRecognizer.getPositionalQueryParameters() );
+			this.namedParameters = toSmallMap( parameterRecognizer.getNamedQueryParameters() );
 		}
 
 		@Override
diff --git a/hibernate-core/src/main/java/org/hibernate/query/sql/internal/ParameterRecognizerImpl.java b/hibernate-core/src/main/java/org/hibernate/query/sql/internal/ParameterRecognizerImpl.java
index d8561de73130..71b66daec418 100644
--- a/hibernate-core/src/main/java/org/hibernate/query/sql/internal/ParameterRecognizerImpl.java
+++ b/hibernate-core/src/main/java/org/hibernate/query/sql/internal/ParameterRecognizerImpl.java
@@ -7,7 +7,6 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.HashMap;
-import java.util.List;
 import java.util.Map;
 
 import org.hibernate.QueryException;
@@ -36,7 +35,7 @@ private enum ParameterStyle {
 
 	private int ordinalParameterImplicitPosition;
 
-	private List<ParameterOccurrence> parameterList;
+	private ArrayList<ParameterOccurrence> parameterList;
 	private final StringBuilder sqlStringBuffer = new StringBuilder();
 
 	public ParameterRecognizerImpl() {
@@ -81,7 +80,7 @@ public Map<Integer, QueryParameterImplementor<?>> getPositionalQueryParameters()
 		return positionalQueryParameters;
 	}
 
-	public List<ParameterOccurrence> getParameterList() {
+	public ArrayList<ParameterOccurrence> getParameterList() {
 		return parameterList;
 	}