[release/7.0] Fix to #30273 - EF7 generating incorrect SQL for the Co…

…ncat/Union All, The same code was working fine for EF6.4.4 (#30451)

Fixed #30273

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

@@ -26,6 +26,10 @@ public sealed partial class SelectExpression : TableExpressionBase
 {
     private const string DiscriminatorColumnAlias = "Discriminator";
     private const string SqlQuerySingleColumnAlias = "Value";
+
+    private static readonly bool UseOldBehavior30273
+        = AppContext.TryGetSwitch("Microsoft.EntityFrameworkCore.Issue30273", out var enabled30273) && enabled30273;
+
     private static readonly IdentifierComparer IdentifierComparerInstance = new();
 
     private static readonly Dictionary<ExpressionType, ExpressionType> MirroredOperationMap =
@@ -3961,6 +3965,14 @@ private SelectExpression Prune(IReadOnlyCollection<string>? referencedColumns)
             }
             else if (table is SetOperationBase { IsDistinct: false } setOperation)
             {
+                if (!UseOldBehavior30273)
+                {
+                    if (setOperation.Source1.IsDistinct
+                        || setOperation.Source2.IsDistinct)
+                    {
+                        continue;
+                    }
+                }
 #if DEBUG
                 setOperation.Source1.Prune(columnsMap[tableAlias], removedAliases);
                 setOperation.Source2.Prune(columnsMap[tableAlias], removedAliases);

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

@@ -877,4 +877,51 @@ public virtual Task Union_on_entity_plus_other_column_with_correlated_collection
                 AssertCollection(e.Orders, a.Orders);
             },
             entryCount: 11);
+
+    [ConditionalTheory]
+    [MemberData(nameof(IsAsyncData))]
+    public virtual Task Concat_with_pruning(bool async)
+        => AssertQuery(
+            async,
+            ss => ss.Set<Customer>().Where(c => c.CustomerID.StartsWith("A"))
+                .Concat(ss.Set<Customer>().Where(c => c.CustomerID.StartsWith("B")))
+                .Select(x => x.City));
+
+    [ConditionalTheory]
+    [MemberData(nameof(IsAsyncData))]
+    public virtual Task Concat_with_distinct_on_one_source_and_pruning(bool async)
+        => AssertQuery(
+            async,
+            ss => ss.Set<Customer>().Where(c => c.CustomerID.StartsWith("A"))
+                .Concat(ss.Set<Customer>().Where(c => c.CustomerID.StartsWith("B")).Distinct())
+                .Select(x => x.City));
+
+    [ConditionalTheory]
+    [MemberData(nameof(IsAsyncData))]
+    public virtual Task Concat_with_distinct_on_both_source_and_pruning(bool async)
+        => AssertQuery(
+            async,
+            ss => ss.Set<Customer>().Where(c => c.CustomerID.StartsWith("A")).Distinct()
+                .Concat(ss.Set<Customer>().Where(c => c.CustomerID.StartsWith("B")).Distinct())
+                .Select(x => x.City));
+
+    [ConditionalTheory]
+    [MemberData(nameof(IsAsyncData))]
+    public virtual Task Nested_concat_with_pruning(bool async)
+        => AssertQuery(
+            async,
+            ss => ss.Set<Customer>().Where(c => c.CustomerID.StartsWith("A"))
+                .Concat(ss.Set<Customer>().Where(c => c.CustomerID.StartsWith("B")))
+                .Concat(ss.Set<Customer>().Where(c => c.CustomerID.StartsWith("A")))
+                .Select(x => x.City));
+
+    [ConditionalTheory]
+    [MemberData(nameof(IsAsyncData))]
+    public virtual Task Nested_concat_with_distinct_in_the_middle_and_pruning(bool async)
+        => AssertQuery(
+            async,
+            ss => ss.Set<Customer>().Where(c => c.CustomerID.StartsWith("A"))
+                .Concat(ss.Set<Customer>().Where(c => c.CustomerID.StartsWith("B")).Distinct())
+                .Concat(ss.Set<Customer>().Where(c => c.CustomerID.StartsWith("A")))
+                .Select(x => x.City));
 }

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

@@ -1317,6 +1317,103 @@ public override async Task Include_Union_different_includes_throws(bool async)
         AssertSql();
     }
 
+    public override async Task Concat_with_pruning(bool async)
+    {
+        await base.Concat_with_pruning(async);
+
+        AssertSql(
+"""
+SELECT [c].[City]
+FROM [Customers] AS [c]
+WHERE [c].[CustomerID] LIKE N'A%'
+UNION ALL
+SELECT [c0].[City]
+FROM [Customers] AS [c0]
+WHERE [c0].[CustomerID] LIKE N'B%'
+""");
+    }
+
+    public override async Task Concat_with_distinct_on_one_source_and_pruning(bool async)
+    {
+        await base.Concat_with_distinct_on_one_source_and_pruning(async);
+
+        AssertSql(
+"""
+SELECT [t].[City]
+FROM (
+    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 [c].[CustomerID] LIKE N'A%'
+    UNION ALL
+    SELECT DISTINCT [c0].[CustomerID], [c0].[Address], [c0].[City], [c0].[CompanyName], [c0].[ContactName], [c0].[ContactTitle], [c0].[Country], [c0].[Fax], [c0].[Phone], [c0].[PostalCode], [c0].[Region]
+    FROM [Customers] AS [c0]
+    WHERE [c0].[CustomerID] LIKE N'B%'
+) AS [t]
+""");
+    }
+
+    public override async Task Concat_with_distinct_on_both_source_and_pruning(bool async)
+    {
+        await base.Concat_with_distinct_on_both_source_and_pruning(async);
+
+        AssertSql(
+"""
+SELECT [t].[City]
+FROM (
+    SELECT DISTINCT [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 [c].[CustomerID] LIKE N'A%'
+    UNION ALL
+    SELECT DISTINCT [c0].[CustomerID], [c0].[Address], [c0].[City], [c0].[CompanyName], [c0].[ContactName], [c0].[ContactTitle], [c0].[Country], [c0].[Fax], [c0].[Phone], [c0].[PostalCode], [c0].[Region]
+    FROM [Customers] AS [c0]
+    WHERE [c0].[CustomerID] LIKE N'B%'
+) AS [t]
+""");
+    }
+
+    public override async Task Nested_concat_with_pruning(bool async)
+    {
+        await base.Nested_concat_with_pruning(async);
+
+        AssertSql(
+"""
+SELECT [c].[City]
+FROM [Customers] AS [c]
+WHERE [c].[CustomerID] LIKE N'A%'
+UNION ALL
+SELECT [c0].[City]
+FROM [Customers] AS [c0]
+WHERE [c0].[CustomerID] LIKE N'B%'
+UNION ALL
+SELECT [c1].[City]
+FROM [Customers] AS [c1]
+WHERE [c1].[CustomerID] LIKE N'A%'
+""");
+    }
+
+    public override async Task Nested_concat_with_distinct_in_the_middle_and_pruning(bool async)
+    {
+        await base.Nested_concat_with_distinct_in_the_middle_and_pruning(async);
+
+        AssertSql(
+"""
+SELECT [t].[City]
+FROM (
+    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 [c].[CustomerID] LIKE N'A%'
+    UNION ALL
+    SELECT DISTINCT [c0].[CustomerID], [c0].[Address], [c0].[City], [c0].[CompanyName], [c0].[ContactName], [c0].[ContactTitle], [c0].[Country], [c0].[Fax], [c0].[Phone], [c0].[PostalCode], [c0].[Region]
+    FROM [Customers] AS [c0]
+    WHERE [c0].[CustomerID] LIKE N'B%'
+) AS [t]
+UNION ALL
+SELECT [c1].[City]
+FROM [Customers] AS [c1]
+WHERE [c1].[CustomerID] LIKE N'A%'
+""");
+    }
+
     public override async Task Client_eval_Union_FirstOrDefault(bool async)
     {
         // Client evaluation in projection. Issue #16243.