Query: Avoid applying entity equality rewrite to subquery coming from…

… let

Resolves #11728

src/EFCore.Specification.Tests/Query/SimpleQueryTestBase.cs

@@ -4258,5 +4258,32 @@ where details.Any()
  select new { Count = details.Count() });
  }
 
+ [ConditionalFact]
+ public virtual void Let_entity_equality_to_null()
+ {
+ AssertQuery<Customer>(
+ cs => from c in cs.Where(c => c.CustomerID.StartsWith("A"))
+ let o = c.Orders.OrderBy(e => e.OrderDate).FirstOrDefault()
+ where o != null
+ select new
+ {
+ c.CustomerID,
+ o.OrderDate
+ });
+ }
+
+ [ConditionalFact]
+ public virtual void Let_entity_equality_to_other_entity()
+ {
+ AssertQuery<Customer>(
+ cs => from c in cs.Where(c => c.CustomerID.StartsWith("A"))
+ let o = c.Orders.OrderBy(e => e.OrderDate).FirstOrDefault()
+ where o != new Order()
+ select new
+ {
+ c.CustomerID,
+ A = (o != null ? o.OrderDate : null)
+ });
+ }
  }
 }

src/EFCore/Query/EntityQueryModelVisitor.cs

@@ -265,6 +265,34 @@ protected virtual void OnBeforeNavigationRewrite([NotNull] QueryModel queryModel
  {
  }
 
+ private class DuplicateQueryModelIdentifyingExpressionVisitor : RelinqExpressionVisitor
+ {
+ private readonly QueryCompilationContext _queryCompilationContext;
+ private ISet<QueryModel> _queryModels = new HashSet<QueryModel>();
+
+ public DuplicateQueryModelIdentifyingExpressionVisitor(QueryCompilationContext queryCompilationContext)
+ {
+ _queryCompilationContext = queryCompilationContext;
+ }
+
+ protected override Expression VisitSubQuery(SubQueryExpression subQueryExpression)
+ {
+ var subQueryModel = subQueryExpression.QueryModel;
+ if (_queryModels.Contains(subQueryModel))
+ {
+ _queryCompilationContext.DuplicateQueryModels.Add(subQueryModel);
+ }
+ else
+ {
+ _queryModels.Add(subQueryModel);
+ }
+
+ subQueryModel.TransformExpressions(Visit);
+
+ return base.VisitSubQuery(subQueryExpression);
+ }
+ }
+
  /// <summary>
  /// Applies optimizations to the query.
  /// </summary>
@@ -276,6 +304,9 @@ protected virtual void OptimizeQueryModel(
  {
  Check.NotNull(queryModel, nameof(queryModel));
 
+ queryModel.TransformExpressions(
+ new DuplicateQueryModelIdentifyingExpressionVisitor(_queryCompilationContext).Visit);
+
  ExtractQueryAnnotations(queryModel);
 
  new EagerLoadingExpressionVisitor(_queryCompilationContext, _querySourceTracingExpressionVisitorFactory)

src/EFCore/Query/ExpressionVisitors/Internal/EntityEqualityRewritingExpressionVisitor.cs

@@ -166,6 +166,11 @@ private Expression RewriteNullEquality(ExpressionType nodeType, Expression nonNu
  Expression.Constant(null)));
  }
 
+ if (IsInvalidSubQueryExpression(nonNullExpression))
+ {
+ return null;
+ }
+
  var entityType = _model.FindEntityType(nonNullExpression.Type)
  ?? GetEntityType(properties, qsre);
 
@@ -220,6 +225,10 @@ var nullConstantExpression
  return Expression.MakeBinary(nodeType, keyAccessExpression, nullConstantExpression);
  }
 
+ private bool IsInvalidSubQueryExpression(Expression expression)
+ => expression is SubQueryExpression subQuery
+ && _queryCompilationContext.DuplicateQueryModels.Contains(subQuery.QueryModel);
+
  private Expression RewriteEntityEquality(ExpressionType nodeType, Expression left, Expression right)
  {
  var leftProperties = MemberAccessBindingExpressionVisitor
@@ -249,6 +258,12 @@ private Expression RewriteEntityEquality(ExpressionType nodeType, Expression lef
  return Expression.Constant(false);
  }
 
+ if (IsInvalidSubQueryExpression(left)
+ || IsInvalidSubQueryExpression(right))
+ {
+ return null;
+ }
+
  var entityType = _model.FindEntityType(left.Type)
  ?? _model.FindEntityType(right.Type)
  ?? GetEntityType(leftProperties, leftQsre)

src/EFCore/Query/ExpressionVisitors/Internal/RequiresMaterializationExpressionVisitor.cs

@@ -192,6 +192,37 @@ protected override Expression VisitMethodCall(MethodCallExpression node)
  return newExpression;
  }
 
+ /// <summary>
+ /// This API supports the Entity Framework Core infrastructure and is not intended to be used
+ /// directly from your code. This API may change or be removed in future releases.
+ /// </summary>
+ protected override Expression VisitBinary(BinaryExpression node)
+ => node.Update(
+ VisitBinaryOperand(node.Left, node.NodeType),
+ node.Conversion,
+ VisitBinaryOperand(node.Right, node.NodeType));
+
+ private Expression VisitBinaryOperand(Expression operand, ExpressionType comparison)
+ {
+ if (comparison == ExpressionType.Equal
+ || comparison == ExpressionType.NotEqual)
+ {
+ if (operand is SubQueryExpression subQueryExpression
+ && _queryModelVisitor.QueryCompilationContext.DuplicateQueryModels.Contains(subQueryExpression.QueryModel))
+ {
+ _queryModelStack.Push(subQueryExpression.QueryModel);
+
+ subQueryExpression.QueryModel.TransformExpressions(Visit);
+
+ _queryModelStack.Pop();
+
+ return operand;
+ }
+ }
+
+ return Visit(operand);
+ }
+
  /// <summary>
  /// This API supports the Entity Framework Core infrastructure and is not intended to be used
  /// directly from your code. This API may change or be removed in future releases.

src/EFCore/Query/QueryCompilationContext.cs

@@ -65,6 +65,8 @@ public QueryCompilationContext(
  TrackQueryResults = trackQueryResults;
  }
 
+ internal ISet<QueryModel> DuplicateQueryModels = new HashSet<QueryModel>();
+
  /// <summary>
  /// Registers a mapping between correlated collection query models and metadata needed to process them.
  /// </summary>

test/EFCore.SqlServer.FunctionalTests/Query/SimpleQuerySqlServerTest.cs

@@ -4514,6 +4514,120 @@ FROM [Order Details] AS [od]
  WHERE ([od].[Quantity] < CAST(10 AS smallint)) AND ([o].[OrderID] = [od].[OrderID]))");
  }
 
+ public override void Let_entity_equality_to_null()
+ {
+ base.Let_entity_equality_to_null();
+
+ AssertSql(
+ @"SELECT [c].[CustomerID], (
+ SELECT TOP(1) [e0].[OrderDate]
+ FROM [Orders] AS [e0]
+ WHERE [c].[CustomerID] = [e0].[CustomerID]
+ ORDER BY [e0].[OrderDate]
+) AS [OrderDate]
+FROM [Customers] AS [c]
+WHERE [c].[CustomerID] LIKE N'A' + N'%' AND (LEFT([c].[CustomerID], LEN(N'A')) = N'A')",
+ //
+ @"@_outer_CustomerID='ALFKI' (Size = 5)
+
+SELECT TOP(1) [e].[OrderID], [e].[CustomerID], [e].[EmployeeID], [e].[OrderDate]
+FROM [Orders] AS [e]
+WHERE @_outer_CustomerID = [e].[CustomerID]
+ORDER BY [e].[OrderDate]",
+ //
+ @"@_outer_CustomerID='ANATR' (Size = 5)
+
+SELECT TOP(1) [e].[OrderID], [e].[CustomerID], [e].[EmployeeID], [e].[OrderDate]
+FROM [Orders] AS [e]
+WHERE @_outer_CustomerID = [e].[CustomerID]
+ORDER BY [e].[OrderDate]",
+ //
+ @"@_outer_CustomerID='ANTON' (Size = 5)
+
+SELECT TOP(1) [e].[OrderID], [e].[CustomerID], [e].[EmployeeID], [e].[OrderDate]
+FROM [Orders] AS [e]
+WHERE @_outer_CustomerID = [e].[CustomerID]
+ORDER BY [e].[OrderDate]",
+ //
+ @"@_outer_CustomerID='AROUT' (Size = 5)
+
+SELECT TOP(1) [e].[OrderID], [e].[CustomerID], [e].[EmployeeID], [e].[OrderDate]
+FROM [Orders] AS [e]
+WHERE @_outer_CustomerID = [e].[CustomerID]
+ORDER BY [e].[OrderDate]");
+ }
+
+ public override void Let_entity_equality_to_other_entity()
+ {
+ base.Let_entity_equality_to_other_entity();
+
+ AssertSql(
+ @"SELECT [c].[CustomerID], (
+ SELECT TOP(1) [e2].[OrderDate]
+ FROM [Orders] AS [e2]
+ WHERE [c].[CustomerID] = [e2].[CustomerID]
+ ORDER BY [e2].[OrderDate]
+)
+FROM [Customers] AS [c]
+WHERE [c].[CustomerID] LIKE N'A' + N'%' AND (LEFT([c].[CustomerID], LEN(N'A')) = N'A')",
+ //
+ @"@_outer_CustomerID='ALFKI' (Size = 5)
+
+SELECT TOP(1) [e].[OrderID], [e].[CustomerID], [e].[EmployeeID], [e].[OrderDate]
+FROM [Orders] AS [e]
+WHERE @_outer_CustomerID = [e].[CustomerID]
+ORDER BY [e].[OrderDate]",
+ //
+ @"@_outer_CustomerID1='ALFKI' (Size = 5)
+
+SELECT TOP(1) [e1].[OrderID], [e1].[CustomerID], [e1].[EmployeeID], [e1].[OrderDate]
+FROM [Orders] AS [e1]
+WHERE @_outer_CustomerID1 = [e1].[CustomerID]
+ORDER BY [e1].[OrderDate]",
+ //
+ @"@_outer_CustomerID='ANATR' (Size = 5)
+
+SELECT TOP(1) [e].[OrderID], [e].[CustomerID], [e].[EmployeeID], [e].[OrderDate]
+FROM [Orders] AS [e]
+WHERE @_outer_CustomerID = [e].[CustomerID]
+ORDER BY [e].[OrderDate]",
+ //
+ @"@_outer_CustomerID1='ANATR' (Size = 5)
+
+SELECT TOP(1) [e1].[OrderID], [e1].[CustomerID], [e1].[EmployeeID], [e1].[OrderDate]
+FROM [Orders] AS [e1]
+WHERE @_outer_CustomerID1 = [e1].[CustomerID]
+ORDER BY [e1].[OrderDate]",
+ //
+ @"@_outer_CustomerID='ANTON' (Size = 5)
+
+SELECT TOP(1) [e].[OrderID], [e].[CustomerID], [e].[EmployeeID], [e].[OrderDate]
+FROM [Orders] AS [e]
+WHERE @_outer_CustomerID = [e].[CustomerID]
+ORDER BY [e].[OrderDate]",
+ //
+ @"@_outer_CustomerID1='ANTON' (Size = 5)
+
+SELECT TOP(1) [e1].[OrderID], [e1].[CustomerID], [e1].[EmployeeID], [e1].[OrderDate]
+FROM [Orders] AS [e1]
+WHERE @_outer_CustomerID1 = [e1].[CustomerID]
+ORDER BY [e1].[OrderDate]",
+ //
+ @"@_outer_CustomerID='AROUT' (Size = 5)
+
+SELECT TOP(1) [e].[OrderID], [e].[CustomerID], [e].[EmployeeID], [e].[OrderDate]
+FROM [Orders] AS [e]
+WHERE @_outer_CustomerID = [e].[CustomerID]
+ORDER BY [e].[OrderDate]",
+ //
+ @"@_outer_CustomerID1='AROUT' (Size = 5)
+
+SELECT TOP(1) [e1].[OrderID], [e1].[CustomerID], [e1].[EmployeeID], [e1].[OrderDate]
+FROM [Orders] AS [e1]
+WHERE @_outer_CustomerID1 = [e1].[CustomerID]
+ORDER BY [e1].[OrderDate]");
+ }
+
  private void AssertSql(params string[] expected)
  => Fixture.TestSqlLoggerFactory.AssertBaseline(expected);