[elephant-devel] Good practices around adding/deleting class slots.

[quan hu]

Hi Yarek,
    Regarding to data migration, it is migration between different stores.

    My understanding of the typical cases are:

     1.  Change the backend. e.g. change BDB to Postmodern .
     2.  Upgrade. e.g. your application uses elephant 0.9.1 and BDB 4.5; To
upgrade elephant from 0.9.1 to 1.0, you need to install BDB 4.7 and run the
migration process.
     3.  Garbage collection. Prior to 1.0, doing a DB migration is the only
way for it. From a recent email, Ian released the online garbage collection
feature in 1.0. It is in experiment status.

Regards
Quan



2009/1/9 Yarek Kowalik <yarek.kowalik at gmail.com>

> In an evolving site there is a fair chance of adding/changing/deleting
> slots from a class.  What are good practices with respect to these actions
> in Elephant?  Are there specific steps that need to be taken to migrate data
> from an old class definition to a new class definition?  Any gotchas one
> needs to be aware of?
>
> BTW, I've read several emails about data migration going by, can someone
> please clarify what exactly "data migration" is?  Is it migrating between
> stores, or different versions of a class?
>
> Yarek
>
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