Query: Lift subqueries projecting single scalar values

Resolves #15705

src/EFCore.Cosmos/Query/Pipeline/CosmosEntityQueryableTranslatorFactory.cs

@@ -26,7 +26,7 @@ public override EntityQueryableTranslator Create(QueryCompilationContext2 queryC
 
     public class CosmosQueryableMethodTranslatingExpressionVisitorFactory : IQueryableMethodTranslatingExpressionVisitorFactory
     {
-        public QueryableMethodTranslatingExpressionVisitor Create(QueryCompilationContext2 queryCompilationContext)
+        public QueryableMethodTranslatingExpressionVisitor Create(IModel model)
         {
             throw new NotImplementedException();
         }

src/EFCore.InMemory/Query/Pipeline/InMemoryProjectionBindingExpressionVisitor.cs

@@ -66,6 +66,8 @@ public override Expression Visit(Expression expression)
                     && methodCall.Arguments[0] is EntityShaperExpression entityShaperExpression
                     && entityShaperExpression.EntityType.GetProperties().Count() == newArrayExpression.Expressions.Count)
                 {
+                    VerifyQueryExpression(entityShaperExpression.ValueBufferExpression);
+
                     _projectionMapping[_projectionMembers.Peek()]
                        = _queryExpression.GetProjectionExpression(
                            entityShaperExpression.ValueBufferExpression.ProjectionMember);
@@ -77,7 +79,7 @@ public override Expression Visit(Expression expression)
 
                 _projectionMapping[_projectionMembers.Peek()] = translation;
 
-                return new ProjectionBindingExpression(_projectionMembers.Peek(), expression.Type);
+                return new ProjectionBindingExpression(_queryExpression, _projectionMembers.Peek(), expression.Type);
             }
 
             return base.Visit(expression);
@@ -87,12 +89,14 @@ protected override Expression VisitExtension(Expression extensionExpression)
         {
             if (extensionExpression is EntityShaperExpression entityShaperExpression)
             {
+                VerifyQueryExpression(entityShaperExpression.ValueBufferExpression);
+
                 _projectionMapping[_projectionMembers.Peek()]
                     = _queryExpression.GetProjectionExpression(
                         entityShaperExpression.ValueBufferExpression.ProjectionMember);
 
                 return entityShaperExpression.Update(
-                    new ProjectionBindingExpression(_projectionMembers.Peek(), typeof(ValueBuffer)));
+                    new ProjectionBindingExpression(_queryExpression, _projectionMembers.Peek(), typeof(ValueBuffer)));
             }
 
             throw new InvalidOperationException();
@@ -132,5 +136,14 @@ protected override Expression VisitMemberInit(MemberInitExpression memberInitExp
 
             return memberInitExpression.Update(newExpression, newBindings);
         }
+
+        // TODO: Debugging
+        private void VerifyQueryExpression(ProjectionBindingExpression projectionBindingExpression)
+        {
+            if (projectionBindingExpression.QueryExpression != _queryExpression)
+            {
+                throw new InvalidOperationException();
+            }
+        }
     }
 }

src/EFCore.InMemory/Query/Pipeline/InMemoryQueryExpression.cs

@@ -90,7 +90,7 @@ public Expression GetSingleScalarProjection()
             _projectionMapping.Clear();
             _projectionMapping[new ProjectionMember()] = _valueBufferSlots[0];
 
-            return new ProjectionBindingExpression(new ProjectionMember(), ServerQueryExpression.Type);
+            return new ProjectionBindingExpression(this, new ProjectionMember(), ServerQueryExpression.Type);
         }
 
         public Expression BindProperty(Expression projectionExpression, IProperty property)

src/EFCore.InMemory/Query/Pipeline/InMemoryQueryableMethodTranslatingExpressionVisitorFactory.cs

@@ -1,13 +1,14 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using Microsoft.EntityFrameworkCore.Metadata;
 using Microsoft.EntityFrameworkCore.Query.Pipeline;
 
 namespace Microsoft.EntityFrameworkCore.InMemory.Query.Pipeline
 {
     public class InMemoryQueryableMethodTranslatingExpressionVisitorFactory : IQueryableMethodTranslatingExpressionVisitorFactory
     {
-        public QueryableMethodTranslatingExpressionVisitor Create(QueryCompilationContext2 queryCompilationContext)
+        public QueryableMethodTranslatingExpressionVisitor Create(IModel model)
         {
             return new InMemoryQueryableMethodTranslatingExpressionVisitor();
         }

src/EFCore.InMemory/Query/Pipeline/InMemoryShapedQueryExpression.cs

@@ -14,7 +14,9 @@ public InMemoryShapedQueryExpression(IEntityType entityType)
             QueryExpression = new InMemoryQueryExpression(entityType);
             ShaperExpression = new EntityShaperExpression(
                 entityType,
-                new ProjectionBindingExpression(new ProjectionMember(), typeof(ValueBuffer)),
+                new ProjectionBindingExpression(
+                    QueryExpression,
+                    new ProjectionMember(), typeof(ValueBuffer)),
                 false);
         }
     }

src/EFCore.Relational/Query/Pipeline/PipeLine/IRelationalSqlTranslatingExpressionVisitorFactory.cs → src/EFCore.Relational/Query/Pipeline/IRelationalSqlTranslatingExpressionVisitorFactory.cs

@@ -2,11 +2,14 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using Microsoft.EntityFrameworkCore.Metadata;
+using Microsoft.EntityFrameworkCore.Query.Pipeline;
 
 namespace Microsoft.EntityFrameworkCore.Relational.Query.Pipeline
 {
     public interface IRelationalSqlTranslatingExpressionVisitorFactory
     {
-        RelationalSqlTranslatingExpressionVisitor Create(IModel model);
+        RelationalSqlTranslatingExpressionVisitor Create(
+            IModel model,
+            IQueryableMethodTranslatingExpressionVisitorFactory queryableMethodTranslatingExpressionVisitorFactory);
     }
 }

src/EFCore.Relational/Query/Pipeline/NullableValueTranslator.cs

@@ -0,0 +1,36 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Reflection;
+using Microsoft.EntityFrameworkCore.Relational.Query.Pipeline.SqlExpressions;
+
+namespace Microsoft.EntityFrameworkCore.Relational.Query.Pipeline
+{
+    public class NullableMemberTranslator : IMemberTranslator
+    {
+        private readonly ISqlExpressionFactory _sqlExpressionFactory;
+
+        public NullableMemberTranslator(ISqlExpressionFactory sqlExpressionFactory)
+        {
+            _sqlExpressionFactory = sqlExpressionFactory;
+        }
+
+        public SqlExpression Translate(SqlExpression instance, MemberInfo member, Type returnType)
+        {
+            if (member.DeclaringType.IsNullableType())
+            {
+                switch (member.Name)
+                {
+                    case nameof(Nullable<int>.Value):
+                        return instance;
+
+                    case nameof(Nullable<int>.HasValue):
+                        return _sqlExpressionFactory.IsNotNull(instance);
+                }
+            }
+
+            return null;
+        }
+    }
+}

src/EFCore.Relational/Query/Pipeline/PipeLine/QuerySqlGenerator.cs → src/EFCore.Relational/Query/Pipeline/QuerySqlGenerator.cs

@@ -635,5 +635,17 @@ protected override Expression VisitLeftJoin(LeftJoinExpression leftJoinExpressio
 
             return leftJoinExpression;
         }
+
+        protected override Expression VisitSubSelect(SubSelectExpression subSelectExpression)
+        {
+            _relationalCommandBuilder.Append("(");
+			using (_relationalCommandBuilder.Indent())
+			{
+				Visit(subSelectExpression.Subquery);
+			}
+            _relationalCommandBuilder.Append(")");
+
+            return subSelectExpression;
+        }
     }
 }

src/EFCore.Relational/Query/Pipeline/PipeLine/RelationalMemberTranslatorProvider.cs → src/EFCore.Relational/Query/Pipeline/RelationalMemberTranslatorProvider.cs

@@ -14,14 +14,15 @@ public class RelationalMemberTranslatorProvider : IMemberTranslatorProvider
         private readonly List<IMemberTranslator> _plugins = new List<IMemberTranslator>();
         private readonly List<IMemberTranslator> _translators = new List<IMemberTranslator>();
 
-        public RelationalMemberTranslatorProvider(IEnumerable<IMemberTranslatorPlugin> plugins)
+        public RelationalMemberTranslatorProvider(ISqlExpressionFactory sqlExpressionFactory,
+            IEnumerable<IMemberTranslatorPlugin> plugins)
         {
             _plugins.AddRange(plugins.SelectMany(p => p.Translators));
             _translators
                 .AddRange(
                 new[]
                 {
-                    new NullableValueTranslator(),
+                    new NullableMemberTranslator(sqlExpressionFactory),
                 });
         }
 

src/EFCore.Relational/Query/Pipeline/PipeLine/RelationalProjectionBindingExpressionVisitor.cs → src/EFCore.Relational/Query/Pipeline/RelationalProjectionBindingExpressionVisitor.cs

@@ -76,18 +76,20 @@ public override Expression Visit(Expression expression)
                     && methodCall.Arguments[0] is EntityShaperExpression entityShaperExpression
                     && entityShaperExpression.EntityType.GetProperties().Count() == newArrayExpression.Expressions.Count)
                 {
+                    VerifySelectExpression(entityShaperExpression.ValueBufferExpression);
+
                     _projectionMapping[_projectionMembers.Peek()]
                        = _selectExpression.GetProjectionExpression(
                            entityShaperExpression.ValueBufferExpression.ProjectionMember);
 
                     return new EntityValuesExpression(entityShaperExpression.EntityType, entityShaperExpression.ValueBufferExpression);
                 }
 
-                var translation = _sqlTranslator.Translate(_selectExpression, expression);
+                var translation = _sqlTranslator.Translate(expression);
 
                 _projectionMapping[_projectionMembers.Peek()] = translation ?? throw new InvalidOperationException();
 
-                return new ProjectionBindingExpression(_projectionMembers.Peek(), expression.Type);
+                return new ProjectionBindingExpression(_selectExpression, _projectionMembers.Peek(), expression.Type);
             }
 
             return base.Visit(expression);
@@ -97,12 +99,14 @@ protected override Expression VisitExtension(Expression extensionExpression)
         {
             if (extensionExpression is EntityShaperExpression entityShaperExpression)
             {
+                VerifySelectExpression(entityShaperExpression.ValueBufferExpression);
+
                 _projectionMapping[_projectionMembers.Peek()]
                     = _selectExpression.GetProjectionExpression(
                         entityShaperExpression.ValueBufferExpression.ProjectionMember);
 
                 return entityShaperExpression.Update(
-                    new ProjectionBindingExpression(_projectionMembers.Peek(), typeof(ValueBuffer)));
+                    new ProjectionBindingExpression(_selectExpression, _projectionMembers.Peek(), typeof(ValueBuffer)));
             }
 
             throw new InvalidOperationException();
@@ -142,5 +146,14 @@ protected override Expression VisitMemberInit(MemberInitExpression memberInitExp
 
             return memberInitExpression.Update(newExpression, newBindings);
         }
+
+        // TODO: Debugging
+        private void VerifySelectExpression(ProjectionBindingExpression projectionBindingExpression)
+        {
+            if (projectionBindingExpression.QueryExpression != _selectExpression)
+            {
+                throw new InvalidOperationException();
+            }
+        }
     }
 }