On Fri, Aug 5, 2011 at 07:17, Joops <john.b...@gmail.com> wrote: > Hi all, > > Just to through my migration hat in the ring. > > I migrated my (non-production app) from MS to HR and it worked fine. > (or at least it seems to have worked fine) > I had used the Key ID's instead of Keys to handle references between > entities. > > Am i correct in saying that the only benefit of using key's over id's > is that you get the nice syntactic sugar way of fetching things?
Keys can also encode the namespace and any partent-child relationship data; if those two things are not a concern then there is effectively no difference. Storing the ids directly is also not-bad because you will not accidentally dereference it leading to lots of inadvertent datastore calls. Your code will be nice and explicit. Robert > > > Thanks very much, > > J. > > On Aug 5, 5:45 am, Robert Kluin <robert.kl...@gmail.com> wrote: >> So here are my thoughts regarding this: if I have to map over all of >> my data re-writing it to prepare it for the tool to convert, why not >> just migrate to the other app while I'm doing that? Otherwise I'm >> going to pay to read and write it to fix it, then pay again to read >> it, transfer it, and rewrite it. This adds up fast if you've got much >> data. >> >> Aside from the cost factor, the migration to HR is an opportunity to >> "fix" or improve your schemas. Things like long field names, unused >> indexes, entity groups, etc.... All of those items that require >> rewriting all of your data to adjust -- the migration is a great time >> to do it. On a migration I've recently been working on, I estimate I >> can reduce our storage use by about 50% with very minor changes (field >> names and indexes!). >> >> I've already migrated a couple apps, each time I've setup a job to map >> over my data, maybe do some conversions, put it in some suitable >> format (like csv or json) then send batches to the new app. On the >> new app side I write a simple 'receiver' handler that does any needed >> conversions and then writes the entities (in batches or one-by-one >> transactionally, depending on the case). >> >> Writing the sender and receiver handlers has usually been pretty quick >> for me, even with very complex data. The other advantage is that you >> may not need to move all of your data. Some items like stats that are >> computed from your original data, may be able to be recomputed by the >> exact same code as it comes in. >> >> Would love to hear other people's thoughts on this. >> >> Robert >> >> >> >> On Thu, Aug 4, 2011 at 21:28, Greg Darke <da...@google.com> wrote: >> > Yes, this is the correctwayto perform this operation. I would >> > suggest adding a new property to the model to store the keys and >> > update your code to use this new property. This will allow you to >> > continue using your application while you are performing your schema >> > migration. >> >> > For example: >> >> > # Old model definition >> > class MyModel(db.Model): >> > links = db.StringListProperty() >> >> > # New model definition >> > class MyModel(db.Model): >> > links = db.StringListProperty() >> > link_keys = db.ListProperty(db.Key) # You may also want to set >> > indexed = False >> >> > def apply_schema_change(self): >> > if not links: >> > # There is nothing to update >> > return >> > self.link_keys = [db.Key(str_key) for str_key in self.links] >> > self.links = [] # We don't use this anymore, so delete the data >> >> > Then you would call the apply_schema_change method after reading the >> > model in from datastore, ensuring that the data is now in the new >> > format. >> >> > Then I would use the mapper framework to apply the new schema to all >> > of the entities in your datastore. >> >> > On 5 August 2011 10:53, Tim Hoffman <zutes...@gmail.com> wrote: >> >> Hi John >> >> I have a db.ListProperty(db.String) or db.StringListProperty and I have >> >> stored keys in it, which of course will be in the str(key) form. >> >> The conversion tools doesn't convert this sort of thing mainly because >> >> unless there is an additional mechanism for >> >> describing what this field holds the conversion tools can't know. >> >> So you would need to something like >> >> Convert all the strings back to keys >> >> keys = [db.Key(i) for i in obj.some_list_property] >> >> then stick them in some property that is defined as >> >> db.ListProperty(db.Key) >> >> Now the trick will be working out the order of events and possibly >> >> performing multiple stages >> >> so you can get you data converted and make the sites work before and after >> >> transfer/conversion >> >> Haven't really worked out the order of events I have to go through. >> >> Rgds >> >> Tim >> >> >> -- >> >> You received this message because you are subscribed to the Google Groups >> >> "Google App Engine" group. >> >> To view this discussion on the web visit >> >>https://groups.google.com/d/msg/google-appengine/-/8_fgPFgpABAJ. >> >> To post to this group, send email to google-appengine@googlegroups.com. >> >> To unsubscribe from this group, send email to >> >> google-appengine+unsubscr...@googlegroups.com. >> >> For more options, visit this group at >> >>http://groups.google.com/group/google-appengine?hl=en. >> >> > -- >> > Greg Darke >> >> > -- >> > You received this message because you are subscribed to the Google Groups >> > "Google App Engine" group. >> > To post to this group, send email to google-appengine@googlegroups.com. >> > To unsubscribe from this group, send email to >> > google-appengine+unsubscr...@googlegroups.com. >> > For more options, visit this group >> > athttp://groups.google.com/group/google-appengine?hl=en.- Hide quoted text >> > - >> >> - Show quoted text - > > -- > You received this message because you are subscribed to the Google Groups > "Google App Engine" group. > To post to this group, send email to google-appengine@googlegroups.com. > To unsubscribe from this group, send email to > google-appengine+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/google-appengine?hl=en. > > -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. 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