From 615267f61ddf8d30a4646f4c63e9f6ea8504e06c Mon Sep 17 00:00:00 2001
From: Marco Belladelli <marco@hibernate.org>
Date: Mon, 13 Mar 2023 17:08:02 +0100
Subject: [PATCH] HHH-16210 Avoid join fetching multiple bag-type collections

---
 .../ast/internal/LoaderSelectBuilder.java     |  6 ++++--
 .../internal/PluralAttributeMappingImpl.java  | 21 +++++++------------
 2 files changed, 12 insertions(+), 15 deletions(-)

diff --git a/hibernate-core/src/main/java/org/hibernate/loader/ast/internal/LoaderSelectBuilder.java b/hibernate-core/src/main/java/org/hibernate/loader/ast/internal/LoaderSelectBuilder.java
index 1e28f45fc0..b1d16b9c00 100644
--- a/hibernate-core/src/main/java/org/hibernate/loader/ast/internal/LoaderSelectBuilder.java
+++ b/hibernate-core/src/main/java/org/hibernate/loader/ast/internal/LoaderSelectBuilder.java
@@ -29,6 +29,7 @@ import org.hibernate.graph.GraphSemantic;
 import org.hibernate.graph.spi.RootGraphImplementor;
 import org.hibernate.loader.ast.spi.Loadable;
 import org.hibernate.loader.ast.spi.Loader;
+import org.hibernate.metamodel.CollectionClassification;
 import org.hibernate.metamodel.mapping.BasicValuedModelPart;
 import org.hibernate.metamodel.mapping.CollectionPart;
 import org.hibernate.metamodel.mapping.EntityIdentifierMapping;
@@ -793,7 +794,8 @@ public class LoaderSelectBuilder {
 			final String bagRole;
 			if ( isFetchablePluralAttributeMapping
 					&& ( (PluralAttributeMapping) fetchable ).getMappedType()
-					.getCollectionSemantics() instanceof BagSemantics ) {
+					.getCollectionSemantics()
+					.getCollectionClassification() == CollectionClassification.BAG ) {
 				bagRole = fetchable.getNavigableRole().getNavigableName();
 			}
 			else {
@@ -801,7 +803,7 @@ public class LoaderSelectBuilder {
 			}
 
 			if ( joined && previousBagRole != null && bagRole != null ) {
-				// Avoid join fetching multiple bags
+				// Avoid join fetching multiple bags to prevent result multiplication
 				joined = false;
 			}
 
diff --git a/hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/PluralAttributeMappingImpl.java b/hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/PluralAttributeMappingImpl.java
index 50428e66f7..8fe858e22d 100644
--- a/hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/PluralAttributeMappingImpl.java
+++ b/hibernate-core/src/main/java/org/hibernate/metamodel/mapping/internal/PluralAttributeMappingImpl.java
@@ -467,26 +467,21 @@ public class PluralAttributeMappingImpl
 	private Fetch createSelectEagerCollectionFetch(
 			FetchParent fetchParent,
 			NavigablePath fetchablePath,
-			DomainResultCreationState creationState, SqlAstCreationState sqlAstCreationState) {
+			DomainResultCreationState creationState,
+			SqlAstCreationState sqlAstCreationState) {
+		final DomainResult<?> collectionKeyDomainResult;
 		if ( referencedPropertyName != null ) {
-			resolveCollectionTableGroup(
-					fetchParent,
-					fetchablePath,
-					creationState,
-					sqlAstCreationState
-			);
-
-			final DomainResult<?> collectionKeyDomainResult = getKeyDescriptor().createTargetDomainResult(
+			collectionKeyDomainResult = getKeyDescriptor().createTargetDomainResult(
 					fetchablePath,
 					sqlAstCreationState.getFromClauseAccess().getTableGroup( fetchParent.getNavigablePath() ),
 					fetchParent,
 					creationState
 			);
-
-			return new SelectEagerCollectionFetch( fetchablePath, this, collectionKeyDomainResult, fetchParent );
-
 		}
-		return new SelectEagerCollectionFetch( fetchablePath, this, null, fetchParent );
+		else {
+			collectionKeyDomainResult = null;
+		}
+		return new SelectEagerCollectionFetch( fetchablePath, this, collectionKeyDomainResult, fetchParent );
 	}
 
 	private TableGroup resolveCollectionTableGroup(