> In other words: if I want to reduce the size of my entities, is
> it necessary to migrate the old entities to ones with the new
> definition?
I'm pretty sure that the answer to that is yes.
> If so, is it sufficient to re-put() the entity, or must I
> save under a wholly new key?
I think that it should be sufficient re-put() but decided to test that
hypothesis.
It isn't sufficient in the SDK - the SDK admin console continues to
show values for properties that you've deleted from the model
definition after the re-put(). Yes, I checked to make sure that those
properties didn't have values before the re-put().
I did the get and re-put() in a transaction, namely:
def txn(key):
obj = Model.get(key)
obj.put()
assert db.run_in_transaction(txn, key)
I tried two things to get around this problem. The first was to add
db.delete(obj.key()) right before obj.put(). (You can't do obj.delete
because that trashes the obj.)
The second was to add "obj.old_property = None" right before the
obj.put() (old_property is the name of the property that I deleted
from Model's definition.)
Neither one worked. According to the SDK's datastore viewer, existing
instances of Model continued to have values for old_property after I
updated them with that transaction even with the two changes, together
or separately.
If this is also true of the production datastore, this is a big deal.
On Oct 10, 4:44 am, Jason Smith <[email protected]> wrote:
> Hi, group. My app's main cost (in dollars and response time) is in the
> db.get([list, of, keys, here]) call in some very high-trafficked code.
> I want to pare down the size of that model to the bare minimum with
> the hope of reducing the time and CPU fee for this very common
> activity. Many users who are experiencing growth in the app popularity
> probably have this objective as well.
>
> I have two questions that hopefully others are thinking about too.
>
> 1. Can I expect the API time of a db.get() with several hundred keys
> to reduce roughly linearly as I reduce the size of the entity?
> Currently the entity has the following data attached: 9 String, 9
> Boolean, 8 Integer, 1 GeoPt, 2 DateTime, 1 Text (avg size ~100 bytes
> FWIW), 1 Reference, 1 StringList (avg size 500 bytes). The goal is to
> move the vast majority of this data to related classes so that the
> core fetch of the main model will be quick.
>
> 2. If I do not change the name of the entity (i.e. just delete all the
> db.*Property definitions in the model), will I still incur the same
> high cost fetching existing entities? The documentation says that all
> properties of a model are fetched simultaneously. Will the old
> unneeded properties still transfer over RPC on my dime and while users
> wait? In other words: if I want to reduce the size of my entities, is
> it necessary to migrate the old entities to ones with the new
> definition? If so, is it sufficient to re-put() the entity, or must I
> save under a wholly new key?
>
> Thanks very much to anyone who knows about this matter!
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