Hi,
Make sure you've read the Java docs carefully: "Datastore entities
are schemaless: Two entities of the same kind are not obligated to
have the same properties".
http://code.google.com/appengine/docs/java/datastore/overview.html#Introducing_the_Java_Datastore
When you change your model definitions, if the changes are not
backwards-compatible, you'll have to write code to iterate over all of
your existing data convert and re-put the entity.
You might want to read through some of the datastore articles:
http://code.google.com/appengine/articles/datastore/overview.html
Specifically,
http://code.google.com/appengine/articles/update_schema.html
Robert
On Mon, Jan 17, 2011 at 10:11, Steel City Phantom <[email protected]> wrote:
> im writing a new app. currently its a LAMP app, heavy on AJAX, but once
> this prototype is done and running i want to rewrite it as an enterprise
> level application. im looking at GAE as a back end (more because ive never
> done it before and it looks cool than anything else, free hosting doesn't
> hurt either) but im struggling with the data store stuff. the biggest
> problem i have so far is changing the data store once its deployed. here is
> what i understand so far, tell me where im wrong cuz im sure i am
> 1 - create your entity objects (this is java)
> 2 - when deployed, GAE will create the data store based on the entity
> objects in your WAR file.
> 3 - use them with googles app engine sql language.
> now, if i want to change the model
> update your entity objects with your new fields or whatever and deploy. now
> GAE should maintain the existing data and update the objects.
> or am i completely off base in thinking like a relational database system.
> is it more as a base relational system that stores blobs and i can store
> whatever i want in them?
> second,
> what if i have a drastic change to the data model that requires some
> translation sql to implement? is there some kind of screen where i can
> query and update the existing data model manually and translate the data
> into the new model or do i have to do it in the application code.
>
> --
> You want it fast, cheap, or right. Pick two!!
>
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