If they're using str(db.Key.from_path('Test', 123)) or
str(entity.key()) it contains the appid (and namespace, kind, and id
or name).
key = db.Key('agVzaGVsbHILCxIEVGVzdBjVAQw')
print key.app()
Should be 'shell'
Robert
On Wed, Feb 23, 2011 at 21:28, Ikai Lan (Google)
<[email protected]> wrote:
> We are unlikely to create a tool that will let you switch from a
> master/slave application to high replication. A data copy will be required.
> As far as master-slave, we will be emphasizing high replication in the
> future and will be basing our uptime metrics on applications running on high
> replication. There will be very few cases, if any, where we will be
> recommending that applications start on master-slave datastore.
> With regards to keys: I don't believe the String form of a Key contains an
> application ID, so if you hash this, the migration should work fine. We
> weren't prepared for your use case, unfortunately, as the migration tool
> takes a key, understand the app ID, rewrite it, and save it to the new
> datastore. We can't do this to a computed hash.
>
> --
> Ikai Lan
> Developer Programs Engineer, Google App Engine
> Blogger: http://googleappengine.blogspot.com
> Reddit: http://www.reddit.com/r/appengine
> Twitter: http://twitter.com/app_engine
>
>
> On Tue, Feb 22, 2011 at 9:44 PM, johnP <[email protected]> wrote:
>>
>> There is lots of thought about how to migrate to HR for the promised
>> increase in reliability. But how do I resolve the following
>> situation. I have millions of entities with a key_name that is a
>> compressed hash of 4 other entity key-strings. This ensures that
>> there are no duplicate records. Also, lots of queries are optimized by
>> pre-building key_names hashes and performing a get.
>>
>> In other words, handling a migration currently appears to require a
>> significant rewrite of key parts of the application, rebuilding
>> millions of entities after the transition, high cpu costs, tons of
>> hackery, headaches, and downtime.
>>
>> The question is (and I've seen multiple attempts from various vectors
>> to ask a similar question): will there be improved tools for
>> migration? Will these improved tools handle my use-case? Will
>> Appengine eventually implement an ability to simply switch a domain
>> from MS to HR? Or simply, Black and White, "John - your application
>> is stuck in a dead-end part of our system. It's your problem to get
>> it out".
>>
>> Is my assumption that Master-Slave is a dead-end, correct?
>>
>> I am hopeful that this question will receive attention because a solid
>> answer, one way or another, is required for planning our resources and
>> development. In other words, instead of further optimizing by moving
>> further in a key_name_hash direction, we'd roll back a bunch of work,
>> perform the transition, then continue.
>>
>> johnP
>>
>>
>> On Feb 1, 10:26 pm, Albert <[email protected]> wrote:
>> > Thank you!
>> >
>> > On Feb 2, 1:30 pm, "Nick Johnson (Google)" <[email protected]>
>> > wrote:
>> >
>> >
>> >
>> >
>> >
>> >
>> >
>> > > Hi Albert,
>> >
>> > > On Wed, Feb 2, 2011 at 12:44 PM, Albert <[email protected]> wrote:
>> > > > Hi!
>> >
>> > > > I just migrated to theHigh Replicationdatastore.
>> >
>> > > > Some of my entities contain stringified keys of other entities.
>> >
>> > > > For example:
>> >
>> > > > Entity(db.Model):
>> > > > owner = db.StringProperty() # the str(Key) of the owner.
>> >
>> > > > Owner(db.Model):
>> > > > name = db.StringProperty()
>> >
>> > > > Now that I've migrated to thehigh-replicationdatastore, all the
>> > > > stringified keys in the Entity Model contain bad keys because the
>> > > > Owner Entities have new keys now.
>> >
>> > > The migration tool rewrites the App ID of keys, but only if they're
>> > > stored
>> > > as keys (or reference properties). This is one reason why you
>> > > shouldn't
>> > > store stringified keys in the datastore!
>> >
>> > > > 2 questions:
>> >
>> > > > 1. Would this have been prevented by using db.ReferenceProperty()
>> > > > instead?
>> >
>> > > Yes.
>> >
>> > > > 2. How can I resolve this issue? I need to update all entities to
>> > > > contain the new keys instead.
>> >
>> > > You should probably use the mapreduce library. For your mapper
>> > > function,
>> > > deserialize the key, and construct a new one with the correct App ID
>> > > (you
>> > > can simply use db.Key.from_path to do this, as it will fill in the App
>> > > ID
>> > > for you) then store it again. You might want to move to using
>> > > ReferenceProperties when you do this.
>> >
>> > > -Nick Johnson
>> >
>> > > > Thanks!
>> >
>> > > > --
>> > > > You received this message because you are subscribed to the Google
>> > > > Groups
>> > > > "Google App Engine" group.
>> > > > To post to this group, send email to
>> > > > [email protected].
>> > > > To unsubscribe from this group, send email to
>> > > >
>> > > > [email protected]<google-appengine%2Bunsubscrib
>> > > > [email protected]>
>> > > > .
>> > > > For more options, visit this group at
>> > > >http://groups.google.com/group/google-appengine?hl=en.
>> >
>> > > --
>> > > Nick Johnson, Developer Programs Engineer, App Engine
>> > > Google Ireland Ltd. :: Registered in Dublin, Ireland, Registration
>> > > Number:
>> > > 368047
>>
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