Remove alias substitution for filtered many-to-many collection in hql (#2538)

It is no longer needed with table group joins

Author: bahusoid

src/NHibernate/Loader/Hql/QueryLoader.cs

@@ -45,7 +45,6 @@ public partial class QueryLoader : BasicLoader
 		private int _selectLength;
 		private LockMode[] _defaultLockModes;
 		private ISet<ICollectionPersister> _uncacheableCollectionPersisters;
-		private Dictionary<string, string[]>[] _collectionUserProvidedAliases;
 		private IReadOnlyDictionary<int, int> _entityByResultTypeDic;
 
 		public QueryLoader(QueryTranslatorImpl queryTranslator, ISessionFactoryImplementor factory, SelectClause selectClause)
@@ -204,11 +203,6 @@ protected internal override ICollectionPersister[] CollectionPersisters
 			get { return _collectionPersisters; }
 		}
 
-		protected override IDictionary<string, string[]> GetCollectionUserProvidedAlias(int index)
-		{
-			return _collectionUserProvidedAliases?[index];
-		}
-
 		private void Initialize(SelectClause selectClause)
 		{
 			IList<FromElement> fromElementList = selectClause.FromElementsForLoad;
@@ -229,8 +223,6 @@ private void Initialize(SelectClause selectClause)
 				_collectionPersisters = new IQueryableCollection[length];
 				_collectionOwners = new int[length];
 				_collectionSuffixes = new string[length];
-				if (collectionFromElements.Any(qc => qc.QueryableCollection.IsManyToMany))
-					_collectionUserProvidedAliases = new Dictionary<string, string[]>[length];
 
 				for (int i = 0; i < length; i++)
 				{
@@ -280,24 +272,6 @@ private void Initialize(SelectClause selectClause)
 					_selectLength++;
 				}
 
-				if (collectionFromElements != null && element.IsFetch && element.QueryableCollection?.IsManyToMany == true
-					&& element.QueryableCollection.IsManyToManyFiltered(_queryTranslator.EnabledFilters))
-				{
-					var collectionIndex = collectionFromElements.IndexOf(element);
-
-					if (collectionIndex >= 0)
-					{
-						// When many-to-many is filtered we need to populate collection from element persister and not from bridge table.
-						// As bridge table will contain not-null values for filtered elements
-						// So do alias substitution for collection persister with element persister
-						// See test TestFilteredLinqQuery for details
-						_collectionUserProvidedAliases[collectionIndex] = new Dictionary<string, string[]>
-						{
-							{CollectionPersister.PropElement, _entityPersisters[i].GetIdentifierAliases(Suffixes[i])}
-						};
-					}
-				}
-
 				_owners[i] = -1; //by default
 				if (element.IsFetch)
 				{

src/NHibernate/Persister/Collection/AbstractCollectionPersister.cs

@@ -1380,7 +1380,9 @@ public string GetManyToManyFilterFragment(string alias, IDictionary<string, IFil
 
 			return buffer.ToString();
 		}
-		
+
+		// Since 5.4
+		[Obsolete("This method has no more usages and will be removed in a future version.")]
 		public bool IsManyToManyFiltered(IDictionary<string, IFilter> enabledFilters)
 		{
 			return IsManyToMany && (manyToManyWhereString != null || manyToManyFilterHelper.IsAffectedBy(enabledFilters));

src/NHibernate/Persister/Collection/ICollectionPersister.cs

@@ -305,18 +305,5 @@ public static int GetBatchSize(this ICollectionPersister persister)
 
 			return 1;
 		}
-
-		/// <summary>
-		/// Is this persister has enabled many-to-many filter or has many-to-many where clause
-		/// </summary>
-		internal static bool IsManyToManyFiltered(this ICollectionPersister persister, IDictionary<string, IFilter> enabledFilters)
-		{
-			if (persister is AbstractCollectionPersister acp)
-			{
-				return acp.IsManyToManyFiltered(enabledFilters);
-			}
-
-			return persister.IsManyToMany && !string.IsNullOrEmpty(persister.GetManyToManyFilterFragment("x", enabledFilters));
-		}
 	}
 }