Question 230618 in PostgreSQL Question posted in
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Postgresql – Why is migration thinking an entry exist on a recently created table?

I am currently trying to add an message column to my table which is modelled to look like this

public class Notification
{
    [Key]
    public Guid Id { get; set; } = Guid.NewGuid();

    public string ActionType { get; set; } = string.Empty;
    public string ActionElement { get; set; } = string.Empty;
    public string ActionElementType { get; set; } = string.Empty;

    public User ForUser { get; set; } = new User();
    public User ByUser { get; set; } = new User();

    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
    public bool Seen { get; set; } = false;
    public bool Clicked { get; set; } = false;

    public Dictionary<string, string>? MessageProperties { get; set; }
    public string Message { get; set; }
}

I want it to look like this

public class Notification
{
    [Key]
    public Guid Id { get; set; } = Guid.NewGuid();

    public string ActionType { get; set; } = string.Empty;
    public string ActionElement { get; set; } = string.Empty;
    public string ActionElementType { get; set; } = string.Empty;

    public User ForUser { get; set; } = new User();
    public User ByUser { get; set; } = new User();

    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
    public bool Seen { get; set; } = false;
    public bool Clicked { get; set; } = false;

    public Dictionary<string, string>? MessageProperties { get; set; }
    public Message MessageContent { get; set; }
}

public record Message
{
    [Key]
    public Guid MessageId { get; set; } = Guid.NewGuid();
    public string? MessageContent { get; init; }
    public Dictionary<string, string>? MessageContentProperties { get; init; }
}

I have via EF managed to make a migrations, but have some issues applying it.

The error message i get when I apply it is

ERROR:  insert or update on table "Notifications" violates foreign key constraint "FK_Notifications_Message_MessageContentMessageId"
DETAIL:  Key (MessageContentMessageId)=(00000000-0000-0000-0000-000000000000) is not present in table "Message".

which I am not sure I understand why and how i should fix.

It fails when it tries to do this

ALTER TABLE "Notifications" 
ADD COLUMN "MessageContentMessageId" uuid DEFAULT uuid_nil() NOT NULL
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2

Answers


  1. 0

    Try making the relationship nullable:

    public Message? MessageContent { get; set; }

    It seems that you have nullable reference types enabled so EF Core will consider the relationship required and will try to insert the default Guid value.

    Read more:

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  2. 0

    first of all remove default value of MessageId and make the MessageId property nullable, then change the Notification class to use the MessageId property from the Message class

    public class Notification
{
    [Key]
    public Guid Id { get; set; } = Guid.NewGuid();

    public string ActionType { get; set; } = string.Empty;
    public string ActionElement { get; set; } = string.Empty;
    public string ActionElementType { get; set; } = string.Empty;

    public User ForUser { get; set; } = new User();
    public User ByUser { get; set; } = new User();

    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
    public bool Seen { get; set; } = false;
    public bool Clicked { get; set; } = false;

    public Dictionary<string, object>? MessageProperties { get; set; }
    public Message? MessageContent { get; set; }
}

public record Message
{
    [Key]
    public Guid? MessageId { get; set; }
    public string? MessageContent { get; init; }
    public Dictionary<string, object>? MessageContentProperties { get; init; }
}

    now generate a new migration and then apply the migration to update the database like below

    dotnet ef migrations add UpdateNotificationMessage
dotnet ef database update
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