Basic FromSql() support in new pipeline

* Parameterization not implemented (see #15750)
* FromSqlRaw() and FromSqlInterpolated() are now defined over DbSet<>,
  not IQueryable<>. FromSql() is still defined over IQueryable<> but
  throws if not directly on a DbSet<>.

Closes #15704

src/EFCore.Relational/Extensions/RelationalQueryableExtensions.cs

@@ -17,9 +17,9 @@ namespace Microsoft.EntityFrameworkCore
     /// </summary>
     public static class RelationalQueryableExtensions
     {
-        internal static readonly MethodInfo FromSqlMethodInfo
+        private static readonly MethodInfo _fromSqlOnQueryableMethodInfo
             = typeof(RelationalQueryableExtensions)
-                .GetTypeInfo().GetDeclaredMethods(nameof(FromSqlRaw))
+                .GetTypeInfo().GetDeclaredMethods(nameof(FromSqlOnQueryable))
                 .Single();
 
         /// <summary>
@@ -54,7 +54,10 @@ internal static readonly MethodInfo FromSqlMethodInfo
         /// <returns> An <see cref="IQueryable{T}" /> representing the raw SQL query. </returns>
         [StringFormatMethod("sql")]
         [Obsolete(
-            "For returning objects from SQL queries using plain strings, use FromSqlRaw instead. For returning objects from SQL queries using interpolated string syntax to create parameters, use FromSqlInterpolated instead.")]
+            "For returning objects from SQL queries using plain strings, use FromSqlRaw instead. " +
+            "For returning objects from SQL queries using interpolated string syntax to create parameters, use FromSqlInterpolated instead. " +
+            "Call either new method directly on the DbSet at the root of the query.",
+            error: true)]
         public static IQueryable<TEntity> FromSql<TEntity>(
             [NotNull] this IQueryable<TEntity> source,
             [NotParameterized] RawSqlString sql,
@@ -68,7 +71,7 @@ public static IQueryable<TEntity> FromSql<TEntity>(
             return source.Provider.CreateQuery<TEntity>(
                 Expression.Call(
                     null,
-                    FromSqlMethodInfo.MakeGenericMethod(typeof(TEntity)),
+                    _fromSqlOnQueryableMethodInfo.MakeGenericMethod(typeof(TEntity)),
                     source.Expression,
                     Expression.Constant(sql.Format),
                     Expression.Constant(parameters)));
@@ -96,7 +99,10 @@ public static IQueryable<TEntity> FromSql<TEntity>(
         /// <param name="sql"> The interpolated string representing a SQL query. </param>
         /// <returns> An <see cref="IQueryable{T}" /> representing the interpolated string SQL query. </returns>
         [Obsolete(
-            "For returning objects from SQL queries using plain strings, use FromSqlRaw instead. For returning objects from SQL queries using interpolated string syntax to create parameters, use FromSqlInterpolated instead.")]
+            "For returning objects from SQL queries using plain strings, use FromSqlRaw instead. " +
+            "For returning objects from SQL queries using interpolated string syntax to create parameters, use FromSqlInterpolated instead. " +
+            "Call either new method directly on the DbSet at the root of the query.",
+            error: true)]
         public static IQueryable<TEntity> FromSql<TEntity>(
             [NotNull] this IQueryable<TEntity> source,
             [NotNull] [NotParameterized] FormattableString sql)
@@ -109,7 +115,7 @@ public static IQueryable<TEntity> FromSql<TEntity>(
             return source.Provider.CreateQuery<TEntity>(
                 Expression.Call(
                     null,
-                    FromSqlMethodInfo.MakeGenericMethod(typeof(TEntity)),
+                    _fromSqlOnQueryableMethodInfo.MakeGenericMethod(typeof(TEntity)),
                     source.Expression,
                     Expression.Constant(sql.Format),
                     Expression.Constant(sql.GetArguments())));
@@ -145,7 +151,7 @@ public static IQueryable<TEntity> FromSql<TEntity>(
         /// <returns> An <see cref="IQueryable{T}" /> representing the raw SQL query. </returns>
         [StringFormatMethod("sql")]
         public static IQueryable<TEntity> FromSqlRaw<TEntity>(
-            [NotNull] this IQueryable<TEntity> source,
+            [NotNull] this DbSet<TEntity> source,
             [NotParameterized] string sql,
             [NotNull] params object[] parameters)
             where TEntity : class
@@ -154,11 +160,12 @@ public static IQueryable<TEntity> FromSqlRaw<TEntity>(
             Check.NotEmpty(sql, nameof(sql));
             Check.NotNull(parameters, nameof(parameters));
 
-            return source.Provider.CreateQuery<TEntity>(
+            var queryableSource = (IQueryable)source;
+            return queryableSource.Provider.CreateQuery<TEntity>(
                 Expression.Call(
                     null,
-                    FromSqlMethodInfo.MakeGenericMethod(typeof(TEntity)),
-                    source.Expression,
+                    _fromSqlOnQueryableMethodInfo.MakeGenericMethod(typeof(TEntity)),
+                    queryableSource.Expression,
                     Expression.Constant(sql),
                     Expression.Constant(parameters)));
         }
@@ -185,21 +192,29 @@ public static IQueryable<TEntity> FromSqlRaw<TEntity>(
         /// <param name="sql"> The interpolated string representing a SQL query with parameters. </param>
         /// <returns> An <see cref="IQueryable{T}" /> representing the interpolated string SQL query. </returns>
         public static IQueryable<TEntity> FromSqlInterpolated<TEntity>(
-            [NotNull] this IQueryable<TEntity> source,
+            [NotNull] this DbSet<TEntity> source,
             [NotNull] [NotParameterized] FormattableString sql)
             where TEntity : class
         {
             Check.NotNull(source, nameof(source));
             Check.NotNull(sql, nameof(sql));
             Check.NotEmpty(sql.Format, nameof(source));
 
-            return source.Provider.CreateQuery<TEntity>(
+            var queryableSource = (IQueryable)source;
+            return queryableSource.Provider.CreateQuery<TEntity>(
                 Expression.Call(
                     null,
-                    FromSqlMethodInfo.MakeGenericMethod(typeof(TEntity)),
-                    source.Expression,
+                    _fromSqlOnQueryableMethodInfo.MakeGenericMethod(typeof(TEntity)),
+                    queryableSource.Expression,
                     Expression.Constant(sql.Format),
                     Expression.Constant(sql.GetArguments())));
         }
+
+        internal static IQueryable<TEntity> FromSqlOnQueryable<TEntity>(
+            [NotNull] this IQueryable<TEntity> source,
+            [NotParameterized] string sql,
+            [NotNull] params object[] parameters)
+            where TEntity : class
+        => throw new NotSupportedException();
     }
 }

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

@@ -216,6 +216,22 @@ protected override Expression VisitTable(TableExpression tableExpression)
             return tableExpression;
         }
 
+        protected override Expression VisitFromSql(FromSqlExpression fromSqlExpression)
+        {
+            _relationalCommandBuilder.AppendLine("(");
+
+            using (_relationalCommandBuilder.Indent())
+            {
+                _relationalCommandBuilder.AppendLines(fromSqlExpression.Sql);
+                // TODO: Generate parameters
+            }
+
+            _relationalCommandBuilder.Append(") AS ")
+                .Append(_sqlGenerationHelper.DelimitIdentifier(fromSqlExpression.Alias));
+
+            return fromSqlExpression;
+        }
+
         protected override Expression VisitSqlBinary(SqlBinaryExpression sqlBinaryExpression)
         {
             if (sqlBinaryExpression.OperatorType == ExpressionType.Coalesce)

src/EFCore.Relational/Query/Pipeline/RelationalEntityQueryableExpressionVisitor2.cs

@@ -2,23 +2,51 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
+using System.Linq;
+using System.Linq.Expressions;
+using Microsoft.EntityFrameworkCore.Diagnostics;
 using Microsoft.EntityFrameworkCore.Metadata;
 using Microsoft.EntityFrameworkCore.Query.Pipeline;
+using Microsoft.EntityFrameworkCore.Internal;
 
 namespace Microsoft.EntityFrameworkCore.Relational.Query.Pipeline
 {
     public class RelationalEntityQueryableExpressionVisitor2 : EntityQueryableExpressionVisitor2
     {
-        private IModel _model;
+        private readonly IModel _model;
 
         public RelationalEntityQueryableExpressionVisitor2(IModel model)
         {
             _model = model;
         }
 
-        protected override ShapedQueryExpression CreateShapedQueryExpression(Type elementType)
+        protected override Expression VisitMethodCall(MethodCallExpression methodCallExpression)
         {
-            return new RelationalShapedQueryExpression(_model.FindEntityType(elementType));
+            if (methodCallExpression.Method.DeclaringType == typeof(RelationalQueryableExtensions)
+                && methodCallExpression.Method.Name == nameof(RelationalQueryableExtensions.FromSqlOnQueryable))
+            {
+                // The obsolete FromSql extension method is still defined as IQueryable (so that users get obsolete warnings),
+                // so we do a runtime check that it's invoked on an EntityQueryable<>. The new FromSqlRaw/FromSqlInterpolated methods
+                // are now defined on DbSet<> instead.
+                if (!(methodCallExpression.Arguments[0] is ConstantExpression constantExpression
+                      && constantExpression.IsEntityQueryable()))
+                {
+                    throw new NotSupportedException(RelationalStrings.FromSqlNotOnDbSet);
+                }
+
+                // TODO: Implement parameters
+                var sql = (string)((ConstantExpression)methodCallExpression.Arguments[1]).Value;
+                var queryable = (IQueryable)((ConstantExpression)methodCallExpression.Arguments[0]).Value;
+                return CreateShapedQueryExpression(queryable.ElementType, sql);
+            }
+
+            return base.VisitMethodCall(methodCallExpression);
         }
+
+        protected override ShapedQueryExpression CreateShapedQueryExpression(Type elementType)
+            => new RelationalShapedQueryExpression(_model.FindEntityType(elementType));
+
+        protected virtual ShapedQueryExpression CreateShapedQueryExpression(Type elementType, string sql)
+            => new RelationalShapedQueryExpression(_model.FindEntityType(elementType), sql);
     }
 }

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

@@ -21,5 +21,17 @@ public RelationalShapedQueryExpression(IEntityType entityType)
                     typeof(ValueBuffer)),
                 false);
         }
+
+        public RelationalShapedQueryExpression(IEntityType entityType, string sql)
+        {
+            QueryExpression = new SelectExpression(entityType, sql);
+            ShaperExpression = new EntityShaperExpression(
+                entityType,
+                new ProjectionBindingExpression(
+                    QueryExpression,
+                    new ProjectionMember(),
+                    typeof(ValueBuffer)),
+                false);
+        }
     }
 }

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

@@ -24,6 +24,9 @@ protected override Expression VisitExtension(Expression extensionExpression)
                 case ExistsExpression existsExpression:
                     return VisitExists(existsExpression);
 
+                case FromSqlExpression fromSqlExpression:
+                    return VisitFromSql(fromSqlExpression);
+
                 case InExpression inExpression:
                     return VisitIn(inExpression);
 
@@ -76,6 +79,7 @@ protected override Expression VisitExtension(Expression extensionExpression)
         protected abstract Expression VisitExists(ExistsExpression existsExpression);
         protected abstract Expression VisitIn(InExpression inExpression);
         protected abstract Expression VisitCrossJoin(CrossJoinExpression crossJoinExpression);
+        protected abstract Expression VisitFromSql(FromSqlExpression fromSqlExpression);
         protected abstract Expression VisitInnerJoin(InnerJoinExpression innerJoinExpression);
         protected abstract Expression VisitLeftJoin(LeftJoinExpression leftJoinExpression);
         protected abstract Expression VisitProjection(ProjectionExpression projectionExpression);

src/EFCore.Relational/Query/Pipeline/SqlExpressions/FromSqlExpression.cs

@@ -0,0 +1,69 @@
+// 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.Linq.Expressions;
+using JetBrains.Annotations;
+using Microsoft.EntityFrameworkCore.Query.Internal;
+
+namespace Microsoft.EntityFrameworkCore.Relational.Query.Pipeline.SqlExpressions
+{
+    public class FromSqlExpression : TableExpressionBase
+    {
+        #region Fields & Constructors
+        public FromSqlExpression(
+            [NotNull] string sql,
+            [NotNull] string alias)
+            : base(alias)
+        {
+            Sql = sql;
+        }
+        #endregion
+
+        #region Public Properties
+
+        /// <summary>
+        ///     Gets the SQL.
+        /// </summary>
+        /// <value>
+        ///     The SQL.
+        /// </value>
+        public string Sql { get; }
+
+        #endregion
+
+        #region Expression-based methods
+
+        protected override Expression VisitChildren(ExpressionVisitor visitor)
+            => this;
+
+        public override void Print(ExpressionPrinter expressionPrinter)
+            => expressionPrinter.StringBuilder.Append(Sql);
+
+        #endregion
+
+        #region Equality & HashCode
+
+        public override bool Equals(object obj)
+            => obj != null
+               && (ReferenceEquals(this, obj)
+                   || obj is FromSqlExpression fromSqlExpression
+                   && Equals(fromSqlExpression));
+
+        private bool Equals(FromSqlExpression fromSqlExpression)
+            => base.Equals(fromSqlExpression)
+               && string.Equals(Sql, fromSqlExpression.Sql);
+
+        public override int GetHashCode()
+        {
+            unchecked
+            {
+                var hashCode = base.GetHashCode();
+                hashCode = (hashCode * 397) ^ Sql.GetHashCode();
+
+                return hashCode;
+            }
+        }
+
+        #endregion
+    }
+}

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

@@ -54,6 +54,18 @@ public SelectExpression(IEntityType entityType)
             _projectionMapping[new ProjectionMember()] = new EntityProjectionExpression(entityType, tableExpression, false);
         }
 
+        public SelectExpression(IEntityType entityType, string sql)
+            : base("")
+        {
+            var fromSqlExpression = new FromSqlExpression(
+                sql,
+                entityType.GetTableName().ToLower().Substring(0, 1));
+
+            _tables.Add(fromSqlExpression);
+
+            _projectionMapping[new ProjectionMember()] = new EntityProjectionExpression(entityType, fromSqlExpression, false);
+        }
+
         public SqlExpression BindProperty(Expression projectionExpression, IProperty property)
         {
             var member = (projectionExpression as ProjectionBindingExpression).ProjectionMember;

src/EFCore.Relational/Query/ResultOperators/Internal/FromSqlExpressionNode.cs

@@ -24,7 +24,10 @@ public class FromSqlExpressionNode : ResultOperatorExpressionNodeBase
         ///     any release. You should only use it directly in your code with extreme caution and knowing that
         ///     doing so can result in application failures when updating to a new Entity Framework Core release.
         /// </summary>
-        public static readonly IReadOnlyCollection<MethodInfo> SupportedMethods = new[] { RelationalQueryableExtensions.FromSqlMethodInfo };
+        public static readonly IReadOnlyCollection<MethodInfo> SupportedMethods = new List<MethodInfo>
+        {
+            // RelationalQueryableExtensions.FromSqlMethodInfo
+        };
 
         private readonly string _sql;
         private readonly Expression _arguments;

src/EFCore.SqlServer/Query/Pipeline/SearchConditionConvertingExpressionVisitor.cs

@@ -91,6 +91,9 @@ protected override Expression VisitExists(ExistsExpression existsExpression)
             return ApplyConversion(existsExpression.Update(subquery), condition: true);
         }
 
+        protected override Expression VisitFromSql(FromSqlExpression fromSqlExpression)
+            => fromSqlExpression;
+
         protected override Expression VisitIn(InExpression inExpression)
         {
             var parentSearchCondition = _isSearchCondition;