[Glass] allSubInstances slow

[Johan Brichau via Glass]

Hi there,

I’m implementing a data migration where I need to do a MyClass allSubInstances, which seems to be very very slow even on a moderately sized database.
I was wonder if there are better practices to achieve this? The class MyClass has many subclasses. 

Is it better do separate the iteration of all those instances per subclass?
I.e.: MySubClassA allInstances do: […]. MySubClassB allInstances do:[…] etc….
Or is there any other way to speed things up here?

thanks
Johan