[Glass] About GsDeployer new doBulkMigrate

[Dale Henrichs]

Sorry for the confusion, but as Martin and James have pointed out, I was
only talking about rebuilding class history:)

It's always possible to make mistakes, so the best course of action is to
use a sand box repository (backup copy of production running in a stone
completely isolated from production) where you test and fine tune all code
update scripts in a completely safe environment.

It always pays to be paranoid when making changes in your production
repository:)

Dale

>

On Wed, Apr 16, 2014 at 8:05 PM, Martin McClure <
martin.mcclure at gemtalksystems.com> wrote:

> On 04/16/2014 04:31 PM, Mariano Martinez Peck wrote:
>
>>     As a final comment ... if for some reason you mess up your class
>>     history, it should be possible to rebuild the class history from the
>>     instances of the old class ... while it is something you don't want
>>     to do ... it's worth keeping in mind that it can be done in an
>>     emergency:)
>>
>>
>> Ahhhh of course...the migrate stuff "just" changes the class pointer of
>> the instances right? So if the slots for XXX instVars were there...they
>> won't get lost. I guess it is similar to Pharo's #adoptInstance: and
>> #primitiveChangeClassTo:
>> Good!
>>
>
> No, I think Dale's comment only applies to recovering classes that have
> been removed from the class history, not to recovering lost values from
> instances due to instvar removal.
>
> Migration of an instance creates a new instance of the new version of the
> class, copies instvar values across, then uses #become: to swap identities
> of the old and new instances. So if an instvar has been removed or renamed
> in the new class version, you *can* lose data with a default migration.
> There are ways to customize migration, but I don't know how those interact
> with GsDeployer.
>
> Regards,
>
> -Martin
>
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