Allow set operations for columns that map to same store type

src/EFCore.Relational/Query/QuerySqlGenerator.cs

@@ -615,9 +615,7 @@ protected override Expression VisitSqlParameter(SqlParameterExpression sqlParame
             p =>
                 p.InvariantName == parameterName
                 && p is TypeMappedRelationalParameter typeMappedRelationalParameter
-                && string.Equals(
-                    typeMappedRelationalParameter.RelationalTypeMapping.StoreType, sqlParameterExpression.TypeMapping!.StoreType,
-                    StringComparison.OrdinalIgnoreCase)
+                && typeMappedRelationalParameter.RelationalTypeMapping.MapsToSameStoreType(sqlParameterExpression.TypeMapping!)
                 && typeMappedRelationalParameter.RelationalTypeMapping.Converter == sqlParameterExpression.TypeMapping!.Converter);
 
         if (parameter is null)

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

@@ -2334,10 +2334,7 @@ private void ApplySetOperation(SetOperationType setOperationType, SelectExpressi
             var innerColumn2 = (SqlExpression)expression2;
             // For now, make sure that both sides output the same store type, otherwise the query may fail.
             // TODO: with #15586 we'll be able to also allow different store types which are implicitly convertible to one another.
-            if (!string.Equals(
-                    innerColumn1.TypeMapping!.StoreType,
-                    innerColumn2.TypeMapping!.StoreType,
-                    StringComparison.OrdinalIgnoreCase))
+            if (!innerColumn1.TypeMapping!.MapsToSameStoreType(innerColumn2.TypeMapping!))
             {
                 throw new InvalidOperationException(RelationalStrings.SetOperationsOnDifferentStoreTypes);
             }

src/EFCore.Relational/Storage/RelationalTypeMapping.cs

@@ -627,4 +627,22 @@ public static MethodInfo GetDataReaderMethod(Type type)
     /// <returns>The expression with customization added.</returns>
     public virtual Expression CustomizeDataReaderExpression(Expression expression)
         => expression;
+
+    /// <inheritdoc />
+    public override bool MapsToSameStoreType(CoreTypeMapping otherMapping)
+    {
+        if (!base.MapsToSameStoreType(otherMapping))
+        {
+            return false;
+        }
+
+        var otherRelationalMapping = ((RelationalTypeMapping)otherMapping);
+        return
+            Size == otherRelationalMapping.Size
+            && Precision == otherRelationalMapping.Precision
+            && DbType == otherRelationalMapping.DbType
+            && Scale == otherRelationalMapping.Scale
+            && IsUnicode == otherRelationalMapping.IsUnicode
+            && IsFixedLength == otherRelationalMapping.IsFixedLength;
+    }
 }

src/EFCore/Storage/CoreTypeMapping.cs

@@ -224,4 +224,14 @@ public virtual ValueComparer ProviderValueComparer
     /// <returns>An expression tree that can be used to generate code for the literal value.</returns>
     public virtual Expression GenerateCodeLiteral(object value)
         => throw new NotSupportedException(CoreStrings.LiteralGenerationNotSupported(ClrType.ShortDisplayName()));
+
+    /// <summary>
+    ///     Determines whether this type mapping is to the same store type as the given mapping.
+    /// </summary>
+    /// <param name="otherMapping">The other type mapping.</param>
+    /// <returns><see langword="true"/> if the two mappings map to the same type, <see langword="false"/> otherwise.</returns>
+    public virtual bool MapsToSameStoreType(CoreTypeMapping otherMapping)
+        => GetType() == otherMapping.GetType()
+            && (Converter?.ProviderClrType ?? ClrType)
+            == (otherMapping.Converter?.ProviderClrType ?? otherMapping.ClrType);
 }

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

@@ -21,7 +21,7 @@ protected override void OnModelCreating(ModelBuilder modelBuilder, DbContext con
                 b.Property(c => c.CustomerID).HasColumnType("nchar(5)");
                 b.Property(cm => cm.CompanyName).HasMaxLength(40);
                 b.Property(cm => cm.ContactName).HasMaxLength(30);
-                b.Property(cm => cm.ContactTitle).HasColumnType("NVarChar(30)");
+                b.Property(cm => cm.ContactTitle).HasColumnType("national character varying(30)");
             });
 
         modelBuilder.Entity<Employee>(

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

@@ -1344,7 +1344,7 @@ public virtual async Task Union_with_different_store_types_throws(bool async)
 
     [ConditionalTheory] // Issue #29020
     [MemberData(nameof(IsAsyncData))]
-    public virtual async Task Union_with_store_types_differing_only_by_case(bool async)
+    public virtual async Task Union_with_type_mappings_to_same_store_type(bool async)
     {
         await AssertQuery(
             async,