Migration tries to create xmin system column

[0xfelaback]

BUG: Migration tries to create xmin system column

ISSUE
When configuring optimistic concurrency by mapping a uint property to PostgreSQL’s xmin/xid, the migration generator incorrectly emits an AddColumn for xmin.

Applying the migration fails with:
column "xmin" conflicts with a system column name

Attempting to work around this by removing the generated defaultValue: 0u does not resolve the issue. Instead, EF Core then fails with:
23502: column "<column_name>" contains null values

This creates a deadlock:

• Keeping the default → conflicts with system column (xmin)
• Removing the default → violates NOT NULL constraint on existing rows

In environments where generated migrations cannot be modified manually, this blocks deployment entirely.

Repro

1. Entity:

public class Account
{
    public int account_id { get; set; }
    public uint Version { get; set; }
}

2. Config:

builder.Property(a => a.Version).IsRowVersion()
       .HasColumnName("xmin")
       .HasColumnType("xid")
       .ValueGeneratedOnAddOrUpdate()
       .IsConcurrencyToken();

3. Run:

dotnet ef migrations add AddConcurrency

4. Generated migration includes:

migrationBuilder.AddColumn<uint>(
    name: "xmin",
    table: "Accounts",
    type: "xid",rowVersion: true,
    nullable: false,
    defaultValue: 0u);

5. Removing defaultValue results in:

23502: column "<column_name>" contains null values

6. Applying migration fails in all cases

EXPECTED
The provider should recognize mappings to PostgreSQL system columns (xmin/xid) and suppress any physical DDL (e.g., AddColumn) for them.

ENVIRONMENT

• PostgreSQL: PostgreSQL16
• Npgsql.EntityFrameworkCore.PostgreSQL: 10.0.1
• .NET: 10.0.201

[roji]

AI Analysis

The generated AddColumn<uint>(name: "xmin", ...) operation is unfortunately expected; EF's model differ still scaffolds it. However, Npgsql's migrations SQL generator special-cases PostgreSQL system columns and should not emit SQL for xmin when applying the migration.

In 10.0.1, AddColumnOperation for xmin should be ignored entirely, so dotnet ef database update should not execute ALTER TABLE ... ADD "xmin" ....

Could you please share the actual generated SQL or verbose dotnet ef database update log, plus the relevant package references? If an ALTER TABLE ... ADD "xmin" statement is actually being executed with Npgsql.EntityFrameworkCore.PostgreSQL 10.0.1, that likely means the Npgsql migrations SQL generator isn't the one being used, or there's a design-time/runtime package mismatch.

[roji]

AI Analysis

I ran a local repro for the existing-table case as well:

1. Created an initial migration with Account mapped without the Version property.
2. Added the reported mapping:

builder.Property(a => a.Version).IsRowVersion()
    .HasColumnName("xmin")
    .HasColumnType("xid")
    .ValueGeneratedOnAddOrUpdate()
    .IsConcurrencyToken();

3. Scaffolded AddConcurrency with dotnet-ef 10.0.1 and Npgsql.EntityFrameworkCore.PostgreSQL 10.0.1.

The C# migration does contain the expected scaffolded operation:

migrationBuilder.AddColumn<uint>(
    name: "xmin",
    table: "Accounts",
    type: "xid",
    rowVersion: true,
    nullable: false,
    defaultValue: 0u);

But dotnet ef migrations script Initial AddConcurrency emits no ALTER TABLE and no xmin SQL; it only inserts the AddConcurrency row into __EFMigrationsHistory. I also applied the two migrations against PostgreSQL 16 in a disposable database, and AddConcurrency completed successfully; the executed commands likewise contained no ALTER TABLE ... ADD "xmin".

So the scaffolded AddColumn is reproducible, but I can't reproduce the actual failing SQL/apply behavior with the provider's migrations SQL generator active. If you're seeing PostgreSQL execute ALTER TABLE ... ADD "xmin", please share the verbose update log and package graph so we can see why the Npgsql generator is not suppressing that operation in your setup.