Hi John, If you do not delete the data that already exists in target app, your target app may wind up with "extra" data that has since been deleted in the source app. Consider the following scenario: - source app has entity, E1 - migration is started, E1 is copied to target app - migration is reverted - source app deletes E1 - migration is restarted, E1 may persist in the target app even though it was removed from the source app
This is the primary reason we suggest you clear the target app's datastore before beginning a migration, to ensure the target app's datastore has the same entities. On Wed, Oct 9, 2013 at 7:52 PM, John Wheeler <[email protected]>wrote: > Can someone, preferably from the app engine team, or who has experience > with this answer the following question: > > I began migrating an M/S datastore app to HRD. It was taking forever > during the 'Copy' phase, so I assumed it was stuck, and I reverted it. It > is now stuck reverting, and I've filed a ticket for that, but that's a > separate issue. > > I missed this part of the documentation, which states: > > "If you want to re-migrate to that target application at a later date, you > must delete the target application's Datastore data." > > What happens if I don't delete the data? It so happens that much of my > data copied over - tens of millions of rows, which would cost hundreds if > not thousands of dollars to delete. I am reluctant to just create a new app > and migrate to it because I already got the mail quota removed from the > current target, and that took a while. > > What happens if you migrate and don't delete the data? Does it overwrite > it? The migration tool gives you the option to perform the migration when > data exists, but it gives you a warning and does specify what will happen > if you don't delete the data. The docs clearly say you 'must' delete the > target data, so I'm wondering technically what the ramifications are. > > If you can answer this question without speculating, I'd be grateful. A > successful migration without any hiccups and 100% data fidelity is very > important to me. > > Thanks, John > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To post to this group, send email to [email protected]. > Visit this group at http://groups.google.com/group/google-appengine. > For more options, visit https://groups.google.com/groups/opt_out. > -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/google-appengine. For more options, visit https://groups.google.com/groups/opt_out.
