简单的1-*关系会导致奇怪的SQL查询

我试图调试EF 6.1.1生成的SQL查询，我已经能够用这少量的代码重现问题。这是一个简单的一对多单向关系，我正在尝试加载:

模型如下:

public class Subscription
{
    public Guid Id { get; set; }
    public IList<Recipient> RecipientHistory { get; set; }
    public IList<Payer> PayerHistory { get; set; }
}
public class Recipient
{
    public Guid Id { get; set; }
}
public class Payer
{
    public Guid Id { get; set; }
}

和EF映射类:

public class SubscriptionMapping : EntityTypeConfiguration<Subscription>
{
    public SubscriptionMapping()
    {
        ToTable("Subscriptions");
        HasKey(p => p.Id);
        Property(p => p.Id).HasColumnName("subscription_id");
        HasMany(p => p.RecipientHistory)
            .WithRequired()
            .Map(m => m.MapKey("subscription_id"));
        HasMany(p => p.PayerHistory)
            .WithRequired()
            .Map(m => m.MapKey("subscription_id"));
    }
}
public class RecipientMapping : EntityTypeConfiguration<Recipient>
{
    public RecipientMapping()
    {
        ToTable("Subscription_recipients");
        HasKey(p => p.Id);
        Property(p => p.Id).HasColumnName("subscription_recipient_id");
    }
}
public class PayerMapping : EntityTypeConfiguration<Payer>
{
    public PayerMapping()
    {
        ToTable("Subscription_payers");
        HasKey(p => p.Id);
        Property(p => p.Id).HasColumnName("subscription_payer_id");
    }
}

当我对商店执行以下查询时:

db.Set<Subscription>()
    .Include(s => s.RecipientHistory)
    .Include(s => s.PayerHistory)
    .ToList();

SELECT 
    [UnionAll1].[C2] AS [C1], 
    [UnionAll1].[subscription_id] AS [C2], 
    [UnionAll1].[C1] AS [C3], 
    [UnionAll1].[C3] AS [C4], 
    [UnionAll1].[subscription_recipient_id] AS [C5], 
    [UnionAll1].[subscription_id1] AS [C6], 
    [UnionAll1].[C4] AS [C7], 
    [UnionAll1].[C5] AS [C8], 
    [UnionAll1].[C6] AS [C9]
    FROM  (SELECT 
        CASE WHEN ([Extent2].[subscription_recipient_id] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1], 
        1 AS [C2], 
        [Extent1].[subscription_id] AS [subscription_id], 
        CASE WHEN ([Extent2].[subscription_recipient_id] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C3], 
        [Extent2].[subscription_recipient_id] AS [subscription_recipient_id], 
        [Extent2].[subscription_id] AS [subscription_id1], 
        CAST(NULL AS int) AS [C4], 
        CAST(NULL AS uniqueidentifier) AS [C5], 
        CAST(NULL AS uniqueidentifier) AS [C6]
        FROM  [dbo].[Subscriptions] AS [Extent1]
        LEFT OUTER JOIN [dbo].[Subscription_recipients] AS [Extent2] ON [Extent1].[subscription_id] = [Extent2].[subscription_id]
    UNION ALL
        SELECT 
        2 AS [C1], 
        2 AS [C2], 
        [Extent3].[subscription_id] AS [subscription_id], 
        CAST(NULL AS int) AS [C3], 
        CAST(NULL AS uniqueidentifier) AS [C4], 
        CAST(NULL AS uniqueidentifier) AS [C5], 
        2 AS [C6], 
        [Extent4].[subscription_payer_id] AS [subscription_payer_id], 
        [Extent4].[subscription_id] AS [subscription_id1]
        FROM  [dbo].[Subscriptions] AS [Extent3]
        INNER JOIN [dbo].[Subscription_payers] AS [Extent4] ON [Extent3].[subscription_id] = [Extent4].[subscription_id]) AS [UnionAll1]
    ORDER BY [UnionAll1].[subscription_id] ASC, [UnionAll1].[C1] ASC

对于这样一个简单的查询，这对我来说似乎是相当不必要的。我是否在映射中遗漏了一些东西，或者这是有意的?