Query: Make it easy to map built-in functions

Resolves #17268

- Introduces new API `IsBuiltIn` on DbFunctionBuilder which marks the function as built-in and we translate it accordingly.
- Add `DbFunctionAttribute.IsBuiltIn` and convention to set the flag appropriately.

src/EFCore.Abstractions/DbFunctionAttribute.cs

@@ -19,6 +19,7 @@ public class DbFunctionAttribute : Attribute
     {
         private string _name;
         private string _schema;
+        private bool _builtIn;
 
         /// <summary>
         ///     Initializes a new instance of the <see cref="DbFunctionAttribute" /> class.
@@ -32,12 +33,14 @@ public DbFunctionAttribute()
         /// </summary>
         /// <param name="name">The name of the function in the database.</param>
         /// <param name="schema">The schema of the function in the database.</param>
-        public DbFunctionAttribute([NotNull] string name, [CanBeNull] string schema = null)
+        /// <param name="builtIn"> The value indicating whether the database function is built-in or not. </param>
+        public DbFunctionAttribute([NotNull] string name, [CanBeNull] string schema = null, bool builtIn = false)
         {
             Check.NotEmpty(name, nameof(name));
 
             _name = name;
             _schema = schema;
+            _builtIn = builtIn;
         }
 
         /// <summary>
@@ -63,5 +66,14 @@ public virtual string Schema
             get => _schema;
             [param: CanBeNull] set => _schema = value;
         }
+
+        /// <summary>
+        ///     The value indicating wheather the database function is built-in or not.
+        /// </summary>
+        public virtual bool IsBuiltIn
+        {
+            get => _builtIn;
+            set => _builtIn = value;
+        }
     }
 }

src/EFCore.Relational/Metadata/Builders/DbFunctionBuilder.cs

@@ -70,6 +70,18 @@ public virtual DbFunctionBuilder HasSchema([CanBeNull] string schema)
             return this;
         }
 
+        /// <summary>
+        ///     Marks whether the database function is built-in or not.
+        /// </summary>
+        /// <param name="builtIn"> The value indicating wheather the database function is built-in or not. </param>
+        /// <returns> The same builder instance so that multiple configuration calls can be chained. </returns>
+        public virtual DbFunctionBuilder IsBuiltIn(bool builtIn = true)
+        {
+            Builder.IsBuiltIn(builtIn, ConfigurationSource.Explicit);
+
+            return this;
+        }
+
         /// <summary>
         ///     Sets the store type of the database function.
         /// </summary>

src/EFCore.Relational/Metadata/Builders/IConventionDbFunctionBuilder.cs

@@ -57,6 +57,25 @@ public interface IConventionDbFunctionBuilder : IConventionAnnotatableBuilder
         /// <returns> <see langword="true" /> if the given schema can be set for the database function. </returns>
         bool CanSetSchema([CanBeNull] string schema, bool fromDataAnnotation = false);
 
+        /// <summary>
+        ///     Sets the value indicating wheather the database function is built-in or not.
+        /// </summary>
+        /// <param name="builtIn"> The value indicating whether the database function is built-in or not. </param>
+        /// <param name="fromDataAnnotation"> Indicates whether the configuration was specified using a data annotation. </param>
+        /// <returns>
+        ///     The same builder instance if the configuration was applied,
+        ///     <see langword="null" /> otherwise.
+        /// </returns>
+        IConventionDbFunctionBuilder IsBuiltIn(bool builtIn, bool fromDataAnnotation = false);
+
+        /// <summary>
+        ///     Returns a value indicating whether the given built-in can be set for the database function.
+        /// </summary>
+        /// <param name="builtIn"> The value indicating whether the database function is built-in or not. </param>
+        /// <param name="fromDataAnnotation"> Indicates whether the configuration was specified using a data annotation. </param>
+        /// <returns> <see langword="true" /> if the given schema can be set for the database function. </returns>
+        bool CanSetIsBuiltIn(bool builtIn, bool fromDataAnnotation = false);
+
         /// <summary>
         ///     Sets the store type of the function in the database.
         /// </summary>

src/EFCore.Relational/Metadata/Conventions/RelationalDbFunctionAttributeConvention.cs

@@ -87,6 +87,11 @@ protected virtual void ProcessDbFunctionAdded(
                 {
                     dbFunctionBuilder.HasSchema(dbFunctionAttribute.Schema, fromDataAnnotation: true);
                 }
+
+                if (dbFunctionAttribute.IsBuiltIn)
+                {
+                    dbFunctionBuilder.IsBuiltIn(dbFunctionAttribute.IsBuiltIn, fromDataAnnotation: true);
+                }
             }
         }
     }

src/EFCore.Relational/Metadata/IConventionDbFunction.cs

@@ -60,6 +60,20 @@ public interface IConventionDbFunction : IConventionAnnotatable, IDbFunction
         /// <returns> The configuration source for <see cref="IDbFunction.Schema" />. </returns>
         ConfigurationSource? GetSchemaConfigurationSource();
 
+        /// <summary>
+        ///     Sets the value indicating wheather the database function is built-in or not.
+        /// </summary>
+        /// <param name="builtIn"> The value indicating whether the database function is built-in or not. </param>
+        /// <param name="fromDataAnnotation"> Indicates whether the configuration was specified using a data annotation. </param>
+        /// <returns> The configured value. </returns>
+        bool SetIsBuiltIn(bool builtIn, bool fromDataAnnotation = false);
+
+        /// <summary>
+        ///     Gets the configuration source for <see cref="IDbFunction.IsBuiltIn" />.
+        /// </summary>
+        /// <returns> The configuration source for <see cref="IDbFunction.IsBuiltIn" />. </returns>
+        ConfigurationSource? GetIsBuiltInConfigurationSource();
+
         /// <summary>
         ///     Sets the store type of the function in the database.
         /// </summary>

src/EFCore.Relational/Metadata/IDbFunction.cs

@@ -25,6 +25,11 @@ public interface IDbFunction : IAnnotatable
         /// </summary>
         string Schema { get; }
 
+        /// <summary>
+        ///     Gets the value indicating wheather the database function is built-in or not.
+        /// </summary>
+        bool IsBuiltIn { get; }
+
         /// <summary>
         ///     Gets the name of the function in the model.
         /// </summary>

src/EFCore.Relational/Metadata/IMutableDbFunction.cs

@@ -25,6 +25,11 @@ public interface IMutableDbFunction : IMutableAnnotatable, IDbFunction
         /// </summary>
         new string Schema { get; [param: CanBeNull] set; }
 
+        /// <summary>
+        ///     Gets or sets the value indicating wheather the database function is built-in or not.
+        /// </summary>
+        new bool IsBuiltIn { get; set; }
+
         /// <summary>
         ///     Gets or sets the store type of the function in the database.
         /// </summary>

src/EFCore.Relational/Metadata/Internal/DbFunction.cs

@@ -29,13 +29,15 @@ public class DbFunction : ConventionAnnotatable, IMutableDbFunction, IConvention
         private readonly List<DbFunctionParameter> _parameters;
         private string _schema;
         private string _name;
+        private bool _builtIn;
         private string _storeType;
         private RelationalTypeMapping _typeMapping;
         private Func<IReadOnlyCollection<SqlExpression>, SqlExpression> _translation;
 
         private ConfigurationSource _configurationSource;
         private ConfigurationSource? _schemaConfigurationSource;
         private ConfigurationSource? _nameConfigurationSource;
+        private ConfigurationSource? _builtInConfigurationSource;
         private ConfigurationSource? _storeTypeConfigurationSource;
         private ConfigurationSource? _typeMappingConfigurationSource;
         private ConfigurationSource? _translationConfigurationSource;
@@ -373,6 +375,40 @@ public virtual string SetName([CanBeNull] string name, ConfigurationSource confi
         /// </summary>
         public virtual ConfigurationSource? GetNameConfigurationSource() => _nameConfigurationSource;
 
+        /// <summary>
+        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+        ///     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 virtual bool IsBuiltIn
+        {
+            get => _builtIn;
+            set => SetIsBuiltIn(value, ConfigurationSource.Explicit);
+        }
+
+        /// <summary>
+        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+        ///     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 virtual bool SetIsBuiltIn(bool builtIn, ConfigurationSource configurationSource)
+        {
+            _builtIn = builtIn;
+            _builtInConfigurationSource = configurationSource.Max(_builtInConfigurationSource);
+
+            return builtIn;
+        }
+
+        /// <summary>
+        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+        ///     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 virtual ConfigurationSource? GetIsBuiltInConfigurationSource() => _builtInConfigurationSource;
+
         /// <summary>
         ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
         ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
@@ -582,6 +618,11 @@ string IConventionDbFunction.SetName(string name, bool fromDataAnnotation)
         string IConventionDbFunction.SetSchema(string schema, bool fromDataAnnotation)
             => SetSchema(schema, fromDataAnnotation ? ConfigurationSource.DataAnnotation : ConfigurationSource.Convention);
 
+        /// <inheritdoc />
+        [DebuggerStepThrough]
+        bool IConventionDbFunction.SetIsBuiltIn(bool builtIn, bool fromDataAnnotation)
+            => SetIsBuiltIn(builtIn, fromDataAnnotation ? ConfigurationSource.DataAnnotation : ConfigurationSource.Convention);
+
         /// <inheritdoc />
         [DebuggerStepThrough]
         string IConventionDbFunction.SetStoreType(string storeType, bool fromDataAnnotation)

src/EFCore.Relational/Metadata/Internal/InternalDbFunctionBuilder.cs

@@ -89,6 +89,33 @@ public virtual bool CanSetSchema([CanBeNull] string schema, ConfigurationSource
             => configurationSource.Overrides(Metadata.GetSchemaConfigurationSource())
                 || Metadata.Schema == schema;
 
+        /// <summary>
+        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+        ///     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 virtual IConventionDbFunctionBuilder IsBuiltIn(bool builtIn, ConfigurationSource configurationSource)
+        {
+            if (CanSetIsBuiltIn(builtIn, configurationSource))
+            {
+                Metadata.SetIsBuiltIn(builtIn, configurationSource);
+                return this;
+            }
+
+            return null;
+        }
+
+        /// <summary>
+        ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
+        ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
+        ///     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 virtual bool CanSetIsBuiltIn(bool builtIn, ConfigurationSource configurationSource)
+            => configurationSource.Overrides(Metadata.GetIsBuiltInConfigurationSource())
+                || Metadata.IsBuiltIn == builtIn;
+
         /// <summary>
         ///     This is an internal API that supports the Entity Framework Core infrastructure and not subject to
         ///     the same compatibility standards as public APIs. It may be changed or removed without notice in
@@ -218,6 +245,16 @@ IConventionDbFunctionBuilder IConventionDbFunctionBuilder.HasSchema(string schem
         bool IConventionDbFunctionBuilder.CanSetSchema(string schema, bool fromDataAnnotation)
             => CanSetSchema(schema, fromDataAnnotation ? ConfigurationSource.DataAnnotation : ConfigurationSource.Convention);
 
+        /// <inheritdoc />
+        [DebuggerStepThrough]
+        IConventionDbFunctionBuilder IConventionDbFunctionBuilder.IsBuiltIn(bool builtIn, bool fromDataAnnotation)
+            => IsBuiltIn(builtIn, fromDataAnnotation ? ConfigurationSource.DataAnnotation : ConfigurationSource.Convention);
+
+        /// <inheritdoc />
+        [DebuggerStepThrough]
+        bool IConventionDbFunctionBuilder.CanSetIsBuiltIn(bool builtIn, bool fromDataAnnotation)
+            => CanSetIsBuiltIn(builtIn, fromDataAnnotation ? ConfigurationSource.DataAnnotation : ConfigurationSource.Convention);
+
         /// <inheritdoc />
         [DebuggerStepThrough]
         IConventionDbFunctionBuilder IConventionDbFunctionBuilder.HasStoreType(string storeType, bool fromDataAnnotation)

src/EFCore.Relational/Query/RelationalMethodCallTranslatorProvider.cs

@@ -70,15 +70,29 @@ public virtual SqlExpression Translate(
             var dbFunction = model.FindDbFunction(method);
             if (dbFunction != null)
             {
-                return dbFunction.Translation?.Invoke(
-                        arguments.Select(e => _sqlExpressionFactory.ApplyDefaultTypeMapping(e)).ToList())
-                    ?? _sqlExpressionFactory.Function(
-                        dbFunction.Schema,
+                if (dbFunction.Translation != null)
+                {
+                    return dbFunction.Translation.Invoke(
+                        arguments.Select(e => _sqlExpressionFactory.ApplyDefaultTypeMapping(e)).ToList());
+                }
+
+                if (dbFunction.IsBuiltIn)
+                {
+                    return _sqlExpressionFactory.Function(
                         dbFunction.Name,
                         arguments,
                         nullable: true,
                         argumentsPropagateNullability: arguments.Select(a => false).ToList(),
                         method.ReturnType);
+                }
+
+                return _sqlExpressionFactory.Function(
+                    dbFunction.Schema,
+                    dbFunction.Name,
+                    arguments,
+                    nullable: true,
+                    argumentsPropagateNullability: arguments.Select(a => false).ToList(),
+                    method.ReturnType);
             }
 
             return _plugins.Concat(_translators)

src/EFCore.SqlServer/Metadata/Conventions/SqlServerDbFunctionConvention.cs

@@ -10,7 +10,8 @@
 namespace Microsoft.EntityFrameworkCore.Metadata.Conventions
 {
     /// <summary>
-    ///     A convention that ensures that <see cref="IDbFunction.Schema"/> is populated for database functions which are not built-in.
+    ///     A convention that ensures that <see cref="IDbFunction.Schema"/> is populated for database functions which
+    ///     have <see cref="IDbFunction.IsBuiltIn"/> flag set to false.
     /// </summary>
     public class SqlServerDbFunctionConvention : IModelFinalizingConvention
     {
@@ -39,7 +40,8 @@ public virtual void ProcessModelFinalizing(IConventionModelBuilder modelBuilder,
         {
             foreach (var dbFunction in modelBuilder.Metadata.GetDbFunctions())
             {
-                if (string.IsNullOrEmpty(dbFunction.Schema))
+                if (!dbFunction.IsBuiltIn
+                    && string.IsNullOrEmpty(dbFunction.Schema))
                 {
                     dbFunction.SetSchema("dbo");
                 }

test/EFCore.Relational.Specification.Tests/Query/UdfDbFunctionTestBase.cs

@@ -94,6 +94,7 @@ public enum ReportingPeriod
                 Fall
             }
 
+            [DbFunction(Name = "len", IsBuiltIn = true)]
             public static long MyCustomLengthStatic(string s) => throw new Exception();
             public static bool IsDateStatic(string date) => throw new Exception();
             public static int AddOneStatic(int num) => num + 1;
@@ -220,15 +221,7 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
                 modelBuilder.HasDbFunction(typeof(UDFSqlContext).GetMethod(nameof(GetSqlFragmentStatic)))
                     .HasTranslation(args => new SqlFragmentExpression("'Two'"));
                 var isDateMethodInfo = typeof(UDFSqlContext).GetMethod(nameof(IsDateStatic));
-                modelBuilder.HasDbFunction(isDateMethodInfo)
-                    .HasTranslation(args => new SqlFunctionExpression(
-                        "IsDate", args, nullable: true, argumentsPropagateNullability: args.Select(a => true).ToList(), isDateMethodInfo.ReturnType, null));
-
-                var methodInfo = typeof(UDFSqlContext).GetMethod(nameof(MyCustomLengthStatic));
-
-                modelBuilder.HasDbFunction(methodInfo)
-                    .HasTranslation(args => new SqlFunctionExpression(
-                        "len", args, nullable: true, argumentsPropagateNullability: args.Select(a => true).ToList(), methodInfo.ReturnType, null));
+                modelBuilder.HasDbFunction(isDateMethodInfo).HasName("IsDate").IsBuiltIn();
 
                 modelBuilder.HasDbFunction(typeof(UDFSqlContext).GetMethod(nameof(AddValues), new[] { typeof(int), typeof(int) }));
 
@@ -244,27 +237,13 @@ protected override void OnModelCreating(ModelBuilder modelBuilder)
                 modelBuilder.HasDbFunction(typeof(UDFSqlContext).GetMethod(nameof(GetReportingPeriodStartDateInstance)))
                     .HasName("GetReportingPeriodStartDate");
                 var isDateMethodInfo2 = typeof(UDFSqlContext).GetMethod(nameof(IsDateInstance));
-                modelBuilder.HasDbFunction(isDateMethodInfo2)
-                    .HasTranslation(args => new SqlFunctionExpression(
-                        "IsDate",
-                        args,
-                        nullable: true,
-                        argumentsPropagateNullability: args.Select(a => true).ToList(),
-                        isDateMethodInfo2.ReturnType,
-                        null));
+                modelBuilder.HasDbFunction(isDateMethodInfo2).HasName("IsDate").IsBuiltIn();
 
                 modelBuilder.HasDbFunction(typeof(UDFSqlContext).GetMethod(nameof(DollarValueInstance))).HasName("DollarValue");
 
                 var methodInfo2 = typeof(UDFSqlContext).GetMethod(nameof(MyCustomLengthInstance));
 
-                modelBuilder.HasDbFunction(methodInfo2)
-                    .HasTranslation(args => new SqlFunctionExpression(
-                        "len",
-                        args,
-                        nullable: true,
-                        argumentsPropagateNullability: args.Select(a => true).ToList(),
-                        methodInfo2.ReturnType,
-                        null));
+                modelBuilder.HasDbFunction(methodInfo2).HasName("len").IsBuiltIn();
 
                 modelBuilder.Entity<MultProductOrders>().ToTable("MultProductOrders").HasKey(mpo => mpo.OrderId);