Cannot rename system column "xmin" about efcore.pg

[roji]

I'm not sure why a RenameColumn operation is getting generated there in the migration - that shouldn't be the case; there's no actual change on the database side here, since xmin is a system column that always has that name and cannot be renamed (as the error message says).

You should be able to just remove the RenameColumn operation from the scaffolded migration and work as usual; to fully understand what's going on I'd need to have a full repro, with the migration snapshot before the migration was added, the full set of instructions, etc. I'm not sure it's worth going into this at this point, unless we see lots of other people running into it...

[mshwf]

Thanks @roji for the support, much appreciated.
I now see why this is confusing, it was hard to reproduce, so I made a clone of the actual project and stripped it down to the slimmest structure, so it contains only the bits that are related to the database. Here is the repo I created (README contains the repro steps):
https://github.com/mshwf/npgsql-rename-xmin-issue

Hope it helps!

[mshwf]

I think I found why this behavior happens with me...
In the OnModelCreating I convert column names to lowercase:

var entityTypes = modelBuilder.Model.GetEntityTypes();
var entityProperties = entityTypes.SelectMany(e => e.GetProperties()).ToList();

foreach (var prop in entityProperties)
{
    var colName = prop.GetColumnName(StoreObjectIdentifier.Table(GetTableName(prop)!, GetSchemaName(prop)!));
    prop.SetColumnName(colName?.ToLower());
}

This includes the new version column as well, so, all I needed is to skip this column:

var entityTypes = modelBuilder.Model.GetEntityTypes();
var entityProperties = entityTypes.SelectMany(e => e.GetProperties()).ToList();

foreach (var prop in entityProperties)
{
    // Concurrency tokens are system columns that we shouldn't try to alter their letter-casing
    if (prop.IsConcurrencyToken) continue;
    var colName = prop.GetColumnName(StoreObjectIdentifier.Table(GetTableName(prop)!, GetSchemaName(prop)!));
    prop.SetColumnName(colName?.ToLower());
}