Optimize away DISTINCT inside IN/EXISTS/set operations

src/EFCore.Relational/Query/RelationalQueryableMethodTranslatingExpressionVisitor.cs

@@ -478,6 +478,7 @@ private static ShapedQueryExpression CreateShapedQueryExpression(IEntityType ent
         {
             subquery.ClearOrdering();
         }
+        subquery.IsDistinct = false;
 
         translation = _sqlExpressionFactory.Not(_sqlExpressionFactory.Exists(subquery));
         subquery = new SelectExpression(translation, _sqlAliasManager);
@@ -509,6 +510,7 @@ private static ShapedQueryExpression CreateShapedQueryExpression(IEntityType ent
         {
             subquery.ClearOrdering();
         }
+        subquery.IsDistinct = false;
 
         var translation = _sqlExpressionFactory.Exists(subquery);
         var selectExpression = new SelectExpression(translation, _sqlAliasManager);
@@ -589,6 +591,7 @@ protected override ShapedQueryExpression TranslateConcat(ShapedQueryExpression s
         {
             subquery.ClearOrdering();
         }
+        subquery.IsDistinct = false;
 
         subquery.ReplaceProjection(new List<Expression> { projection });
         subquery.ApplyProjection();

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

@@ -189,7 +189,7 @@ public static SelectExpression CreateImmutable(string alias, List<TableExpressio
     /// <summary>
     ///     A bool value indicating if DISTINCT is applied to projection of this <see cref="SelectExpression" />.
     /// </summary>
-    public bool IsDistinct { get; private set; }
+    public bool IsDistinct { get; set; }
 
     /// <summary>
     ///     The list of expressions being projected out from the result set.
@@ -2006,6 +2006,12 @@ private void ApplySetOperation(
             select2.ClearOrdering();
         }
 
+        if (distinct)
+        {
+            select1.IsDistinct = false;
+            select2.IsDistinct = false;
+        }
+
         if (_clientProjections.Count > 0
             || select2._clientProjections.Count > 0)
         {

test/EFCore.Cosmos.FunctionalTests/Query/NorthwindMiscellaneousQueryCosmosTest.cs

@@ -887,6 +887,30 @@ public override async Task Any_with_multiple_conditions_still_uses_exists(bool a
         AssertSql();
     }
 
+    public override async Task Any_on_distinct(bool async)
+    {
+        // Cosmos client evaluation. Issue #17246.
+        await AssertTranslationFailed(() => base.Any_on_distinct(async));
+
+        AssertSql();
+    }
+
+    public override async Task Contains_on_distinct(bool async)
+    {
+        // Cosmos client evaluation. Issue #17246.
+        await AssertTranslationFailed(() => base.Contains_on_distinct(async));
+
+        AssertSql();
+    }
+
+    public override async Task All_on_distinct(bool async)
+    {
+        // Cosmos client evaluation. Issue #17246.
+        await AssertTranslationFailed(() => base.All_on_distinct(async));
+
+        AssertSql();
+    }
+
     public override async Task All_top_level(bool async)
     {
         // Cosmos client evaluation. Issue #17246.
@@ -3675,7 +3699,7 @@ public override async Task SelectMany_primitive_select_subquery(bool async)
         // Cosmos client evaluation. Issue #17246.
         Assert.Equal(
             CoreStrings.ExpressionParameterizationExceptionSensitive(
-                "value(Microsoft.EntityFrameworkCore.Query.NorthwindMiscellaneousQueryTestBase`1+<>c__DisplayClass169_0[Microsoft.EntityFrameworkCore.Query.NorthwindQueryCosmosFixture`1[Microsoft.EntityFrameworkCore.TestUtilities.NoopModelCustomizer]]).ss.Set().Any()"),
+                "value(Microsoft.EntityFrameworkCore.Query.NorthwindMiscellaneousQueryTestBase`1+<>c__DisplayClass172_0[Microsoft.EntityFrameworkCore.Query.NorthwindQueryCosmosFixture`1[Microsoft.EntityFrameworkCore.TestUtilities.NoopModelCustomizer]]).ss.Set().Any()"),
             (await Assert.ThrowsAsync<InvalidOperationException>(
                 () => base.SelectMany_primitive_select_subquery(async))).Message);
 

test/EFCore.Specification.Tests/Query/NorthwindMiscellaneousQueryTestBase.cs

@@ -953,6 +953,27 @@ public virtual Task Any_with_multiple_conditions_still_uses_exists(bool async)
             async,
             ss => ss.Set<Customer>().Where(c => c.City == "London" && c.Orders.Any(o => o.EmployeeID == 1)));
 
+    [ConditionalTheory]
+    [MemberData(nameof(IsAsyncData))]
+    public virtual Task Any_on_distinct(bool async)
+        => AssertQuery(
+            async,
+            ss => ss.Set<Customer>().Where(c => c.Orders.Select(o => o.EmployeeID).Distinct().Any(id => id != 1)));
+
+    [ConditionalTheory]
+    [MemberData(nameof(IsAsyncData))]
+    public virtual Task Contains_on_distinct(bool async)
+        => AssertQuery(
+            async,
+            ss => ss.Set<Customer>().Where(c => c.Orders.Select(o => o.EmployeeID).Distinct().Contains(1u)));
+
+    [ConditionalTheory]
+    [MemberData(nameof(IsAsyncData))]
+    public virtual Task All_on_distinct(bool async)
+        => AssertQuery(
+            async,
+            ss => ss.Set<Customer>().Where(c => c.Orders.Select(o => o.EmployeeID).Distinct().All(id => id != 1)));
+
     [ConditionalTheory]
     [MemberData(nameof(IsAsyncData))]
     public virtual Task All_top_level(bool async)

test/EFCore.Specification.Tests/Query/NorthwindSetOperationsQueryTestBase.cs

@@ -366,6 +366,48 @@ public virtual Task Select_Except_reference_projection(bool async)
                         .Where(o => o.CustomerID == "ALFKI")
                         .Select(o => o.Customer)));
 
+    [ConditionalTheory]
+    [MemberData(nameof(IsAsyncData))]
+    public virtual Task Intersect_on_distinct(bool async)
+        => AssertQuery(
+            async,
+            ss => ss.Set<Customer>()
+                .Where(c => c.City == "México D.F.")
+                .Select(c => c.CompanyName)
+                .Distinct()
+                .Intersect(
+                    ss.Set<Customer>()
+                        .Where(s => s.ContactTitle == "Owner")
+                        .Select(c => c.CompanyName)));
+
+    [ConditionalTheory]
+    [MemberData(nameof(IsAsyncData))]
+    public virtual Task Union_on_distinct(bool async)
+        => AssertQuery(
+            async,
+            ss => ss.Set<Customer>()
+                .Where(c => c.City == "México D.F.")
+                .Select(c => c.CompanyName)
+                .Distinct()
+                .Union(
+                    ss.Set<Customer>()
+                        .Where(s => s.ContactTitle == "Owner")
+                        .Select(c => c.CompanyName)));
+
+    [ConditionalTheory]
+    [MemberData(nameof(IsAsyncData))]
+    public virtual Task Except_on_distinct(bool async)
+        => AssertQuery(
+            async,
+            ss => ss.Set<Customer>()
+                .Where(c => c.City == "México D.F.")
+                .Select(c => c.CompanyName)
+                .Distinct()
+                .Except(
+                    ss.Set<Customer>()
+                        .Where(s => s.ContactTitle == "Owner")
+                        .Select(c => c.CompanyName)));
+
     [ConditionalTheory]
     [MemberData(nameof(IsAsyncData))]
     public virtual async Task Include_Union_only_on_one_side_throws(bool async)

test/EFCore.SqlServer.FunctionalTests/Query/ComplexNavigationsQuerySqlServer160Test.cs

@@ -2068,7 +2068,7 @@ public override async Task Contains_with_subquery_optional_navigation_scalar_dis
 FROM [LevelOne] AS [l]
 LEFT JOIN [LevelTwo] AS [l0] ON [l].[Id] = [l0].[Level1_Optional_Id]
 WHERE 5 IN (
-    SELECT DISTINCT CAST(LEN([l1].[Name]) AS int)
+    SELECT CAST(LEN([l1].[Name]) AS int)
     FROM [LevelThree] AS [l1]
     WHERE [l0].[Id] IS NOT NULL AND [l0].[Id] = [l1].[OneToMany_Optional_Inverse3Id]
 )

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

@@ -2068,7 +2068,7 @@ public override async Task Contains_with_subquery_optional_navigation_scalar_dis
 FROM [LevelOne] AS [l]
 LEFT JOIN [LevelTwo] AS [l0] ON [l].[Id] = [l0].[Level1_Optional_Id]
 WHERE 5 IN (
-    SELECT DISTINCT CAST(LEN([l1].[Name]) AS int)
+    SELECT CAST(LEN([l1].[Name]) AS int)
     FROM [LevelThree] AS [l1]
     WHERE [l0].[Id] IS NOT NULL AND [l0].[Id] = [l1].[OneToMany_Optional_Inverse3Id]
 )

test/EFCore.SqlServer.FunctionalTests/Query/ComplexNavigationsSharedTypeQuerySqlServer160Test.cs

@@ -2117,7 +2117,7 @@ FROM [Level1] AS [l0]
     WHERE [l0].[OneToOne_Required_PK_Date] IS NOT NULL AND [l0].[Level1_Required_Id] IS NOT NULL AND [l0].[OneToMany_Required_Inverse2Id] IS NOT NULL
 ) AS [l1] ON [l].[Id] = [l1].[Level1_Optional_Id]
 WHERE 5 IN (
-    SELECT DISTINCT CAST(LEN([l2].[Level3_Name]) AS int)
+    SELECT CAST(LEN([l2].[Level3_Name]) AS int)
     FROM [Level1] AS [l2]
     WHERE [l2].[Level2_Required_Id] IS NOT NULL AND [l2].[OneToMany_Required_Inverse3Id] IS NOT NULL AND CASE
         WHEN [l1].[OneToOne_Required_PK_Date] IS NOT NULL AND [l1].[Level1_Required_Id] IS NOT NULL AND [l1].[OneToMany_Required_Inverse2Id] IS NOT NULL THEN [l1].[Id]

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

@@ -2119,7 +2119,7 @@ FROM [Level1] AS [l0]
     WHERE [l0].[OneToOne_Required_PK_Date] IS NOT NULL AND [l0].[Level1_Required_Id] IS NOT NULL AND [l0].[OneToMany_Required_Inverse2Id] IS NOT NULL
 ) AS [l1] ON [l].[Id] = [l1].[Level1_Optional_Id]
 WHERE 5 IN (
-    SELECT DISTINCT CAST(LEN([l2].[Level3_Name]) AS int)
+    SELECT CAST(LEN([l2].[Level3_Name]) AS int)
     FROM [Level1] AS [l2]
     WHERE [l2].[Level2_Required_Id] IS NOT NULL AND [l2].[OneToMany_Required_Inverse3Id] IS NOT NULL AND CASE
         WHEN [l1].[OneToOne_Required_PK_Date] IS NOT NULL AND [l1].[Level1_Required_Id] IS NOT NULL AND [l1].[OneToMany_Required_Inverse2Id] IS NOT NULL THEN [l1].[Id]

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

@@ -1603,6 +1603,52 @@ FROM [Orders] AS [o]
 """);
     }
 
+    public override async Task Any_on_distinct(bool async)
+    {
+        await base.Any_on_distinct(async);
+
+        AssertSql(
+            """
+SELECT [c].[CustomerID], [c].[Address], [c].[City], [c].[CompanyName], [c].[ContactName], [c].[ContactTitle], [c].[Country], [c].[Fax], [c].[Phone], [c].[PostalCode], [c].[Region]
+FROM [Customers] AS [c]
+WHERE EXISTS (
+    SELECT 1
+    FROM [Orders] AS [o]
+    WHERE [c].[CustomerID] = [o].[CustomerID] AND ([o].[EmployeeID] <> 1 OR [o].[EmployeeID] IS NULL))
+""");
+    }
+
+    public override async Task Contains_on_distinct(bool async)
+    {
+        await base.Contains_on_distinct(async);
+
+        AssertSql(
+            """
+SELECT [c].[CustomerID], [c].[Address], [c].[City], [c].[CompanyName], [c].[ContactName], [c].[ContactTitle], [c].[Country], [c].[Fax], [c].[Phone], [c].[PostalCode], [c].[Region]
+FROM [Customers] AS [c]
+WHERE 1 IN (
+    SELECT [o].[EmployeeID]
+    FROM [Orders] AS [o]
+    WHERE [c].[CustomerID] = [o].[CustomerID]
+)
+""");
+    }
+
+    public override async Task All_on_distinct(bool async)
+    {
+        await base.All_on_distinct(async);
+
+        AssertSql(
+            """
+SELECT [c].[CustomerID], [c].[Address], [c].[City], [c].[CompanyName], [c].[ContactName], [c].[ContactTitle], [c].[Country], [c].[Fax], [c].[Phone], [c].[PostalCode], [c].[Region]
+FROM [Customers] AS [c]
+WHERE NOT EXISTS (
+    SELECT 1
+    FROM [Orders] AS [o]
+    WHERE [c].[CustomerID] = [o].[CustomerID] AND [o].[EmployeeID] = 1)
+""");
+    }
+
     public override async Task All_top_level(bool async)
     {
         await base.All_top_level(async);
@@ -4061,7 +4107,7 @@ WHERE EXISTS (
         SELECT 1
         FROM [Customers] AS [c1]
         WHERE EXISTS (
-            SELECT DISTINCT 1
+            SELECT 1
             FROM (
                 SELECT TOP(10) 1 AS empty
                 FROM [Customers] AS [c2]
@@ -7263,7 +7309,7 @@ FROM OPENJSON(@__ids_0) WITH ([value] int '$') AS [i0]
 
     public override async Task Contains_over_concatenated_columns_with_different_sizes(bool async)
     {
-        await base.Contains_over_concatenated_columns_with_different_sizes (async);
+        await base.Contains_over_concatenated_columns_with_different_sizes(async);
 
         AssertSql(
             """
@@ -7280,7 +7326,7 @@ FROM OPENJSON(@__data_0) WITH ([value] nvarchar(45) '$') AS [d]
 
     public override async Task Contains_over_concatenated_column_and_constant(bool async)
     {
-        await base.Contains_over_concatenated_column_and_constant (async);
+        await base.Contains_over_concatenated_column_and_constant(async);
 
         AssertSql(
             """

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

@@ -1370,6 +1370,54 @@ public override async Task Collection_projection_before_set_operation_fails(bool
         AssertSql();
     }
 
+    public override async Task Intersect_on_distinct(bool async)
+    {
+        await base.Intersect_on_distinct(async);
+
+        AssertSql(
+            """
+SELECT [c].[CompanyName]
+FROM [Customers] AS [c]
+WHERE [c].[City] = N'México D.F.'
+INTERSECT
+SELECT [c0].[CompanyName]
+FROM [Customers] AS [c0]
+WHERE [c0].[ContactTitle] = N'Owner'
+""");
+    }
+
+    public override async Task Union_on_distinct(bool async)
+    {
+        await base.Union_on_distinct(async);
+
+        AssertSql(
+            """
+SELECT [c].[CompanyName]
+FROM [Customers] AS [c]
+WHERE [c].[City] = N'México D.F.'
+UNION
+SELECT [c0].[CompanyName]
+FROM [Customers] AS [c0]
+WHERE [c0].[ContactTitle] = N'Owner'
+""");
+    }
+
+    public override async Task Except_on_distinct(bool async)
+    {
+        await base.Except_on_distinct(async);
+
+        AssertSql(
+            """
+SELECT [c].[CompanyName]
+FROM [Customers] AS [c]
+WHERE [c].[City] = N'México D.F.'
+EXCEPT
+SELECT [c0].[CompanyName]
+FROM [Customers] AS [c0]
+WHERE [c0].[ContactTitle] = N'Owner'
+""");
+    }
+
     public override async Task Include_Union_only_on_one_side_throws(bool async)
     {
         await base.Include_Union_only_on_one_side_throws(async);