[release/3.1] Query: Map projection properly when joining 2 tables

src/EFCore.Relational/Query/SqlExpressions/SelectExpression.cs

@@ -914,9 +914,11 @@ public Expression ApplyCollectionJoin(
             }
 
             var indexOffset = _projection.Count;
-            foreach (var projection in innerSelectExpression.Projection)
+            var innerProjectionCount = innerSelectExpression.Projection.Count;
+            var indexMap = new int[innerProjectionCount];
+            for (var i = 0; i < innerProjectionCount; i++)
             {
-                AddToProjection(MakeNullable(projection.Expression));
+                indexMap[i] = AddToProjection(MakeNullable(innerSelectExpression.Projection[i].Expression));
             }
 
             foreach (var identifier in innerSelectExpression._identifier.Concat(innerSelectExpression._childIdentifiers))
@@ -926,7 +928,10 @@ public Expression ApplyCollectionJoin(
                 AppendOrdering(new OrderingExpression(updatedColumn, ascending: true));
             }
 
-            var shaperRemapper = new ShaperRemappingExpressionVisitor(this, innerSelectExpression, indexOffset);
+            var shaperRemapper = AppContext.TryGetSwitch("Microsoft.EntityFrameworkCore.Issue19616", out var isEnabled)
+                && isEnabled
+                ? new ShaperRemappingExpressionVisitor(this, innerSelectExpression, indexOffset)
+                : new ShaperRemappingExpressionVisitor(this, innerSelectExpression, indexMap);
             innerShaper = shaperRemapper.Visit(innerShaper);
             selfIdentifier = shaperRemapper.Visit(selfIdentifier);
 
@@ -961,21 +966,32 @@ private class ShaperRemappingExpressionVisitor : ExpressionVisitor
             private readonly SelectExpression _queryExpression;
             private readonly SelectExpression _innerSelectExpression;
             private readonly int _offset;
+            private readonly int[] _indexMap;
 
-            public ShaperRemappingExpressionVisitor(SelectExpression queryExpression, SelectExpression innerSelectExpression, int offset)
+            public ShaperRemappingExpressionVisitor(
+                SelectExpression queryExpression, SelectExpression innerSelectExpression, int offset)
             {
                 _queryExpression = queryExpression;
                 _innerSelectExpression = innerSelectExpression;
                 _offset = offset;
             }
 
+            public ShaperRemappingExpressionVisitor(
+                SelectExpression queryExpression, SelectExpression innerSelectExpression, int[] indexMap)
+            {
+                _queryExpression = queryExpression;
+                _innerSelectExpression = innerSelectExpression;
+                _indexMap = indexMap;
+            }
+
             protected override Expression VisitExtension(Expression extensionExpression)
             {
                 if (extensionExpression is ProjectionBindingExpression projectionBindingExpression)
                 {
                     var oldIndex = (int)GetProjectionIndex(projectionBindingExpression);
+                    var newIndex = _indexMap?[oldIndex] ?? oldIndex + _offset;
 
-                    return new ProjectionBindingExpression(_queryExpression, oldIndex + _offset, projectionBindingExpression.Type);
+                    return new ProjectionBindingExpression(_queryExpression, newIndex, projectionBindingExpression.Type);
                 }
 
                 if (extensionExpression is EntityShaperExpression entityShaper)
@@ -985,7 +1001,8 @@ protected override Expression VisitExtension(Expression extensionExpression)
                     var indexMap = new Dictionary<IProperty, int>();
                     foreach (var keyValuePair in oldIndexMap)
                     {
-                        indexMap[keyValuePair.Key] = keyValuePair.Value + _offset;
+                        var oldIndex = keyValuePair.Value;
+                        indexMap[keyValuePair.Key] = _indexMap?[oldIndex] ?? oldIndex + _offset;
                     }
 
                     return new EntityShaperExpression(

test/EFCore.Cosmos.FunctionalTests/Query/SimpleQueryCosmosTest.Select.cs

@@ -921,5 +921,11 @@ public override Task LastOrDefault_member_access_in_projection_translates_to_ser
         {
             return base.LastOrDefault_member_access_in_projection_translates_to_server(isAsync);
         }
+
+        [ConditionalTheory(Skip = "Issue#17246")]
+        public override Task Projecting_multiple_collection_with_same_constant_works(bool async)
+        {
+            return base.Projecting_multiple_collection_with_same_constant_works(async);
+        }
     }
 }

test/EFCore.Specification.Tests/Query/SimpleQueryTestBase.Select.cs

@@ -1492,5 +1492,25 @@ public CustomerWrapper2(Customer customer)
             public string City { get; set; }
             public Customer Customer { get; }
         }
+
+        [ConditionalTheory]
+        [MemberData(nameof(IsAsyncData))]
+        public virtual Task Projecting_multiple_collection_with_same_constant_works(bool async)
+        {
+            return AssertQuery(
+                async,
+                ss => ss.Set<Customer>().Where(c => c.CustomerID == "ALFKI")
+                    .Select(c => new
+                    {
+                        O1 = c.Orders.Select(e => new { Value = 1 }),
+                        O2 = c.Orders.Select(e => new { AnotherValue = 1 })
+                    }),
+                assertOrder: true, //single element
+                elementAsserter: (e, a) =>
+                {
+                    AssertCollection(e.O1, a.O1, ordered: true);
+                    AssertCollection(e.O2, a.O2, ordered: true);
+                });
+        }
     }
 }

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

@@ -1227,5 +1227,18 @@ FROM [Orders] AS [o]
 FROM [Customers] AS [c]
 WHERE [c].[CustomerID] LIKE N'A%'");
         }
+
+        public override async Task Projecting_multiple_collection_with_same_constant_works(bool async)
+        {
+            await base.Projecting_multiple_collection_with_same_constant_works(async);
+
+            AssertSql(
+                @"SELECT [c].[CustomerID], 1, [o].[OrderID], [o0].[OrderID]
+FROM [Customers] AS [c]
+LEFT JOIN [Orders] AS [o] ON [c].[CustomerID] = [o].[CustomerID]
+LEFT JOIN [Orders] AS [o0] ON [c].[CustomerID] = [o0].[CustomerID]
+WHERE [c].[CustomerID] = N'ALFKI'
+ORDER BY [c].[CustomerID], [o].[OrderID], [o0].[OrderID]");
+        }
     }
 }