[appengine-java] Re: on switching a webapp from RDBMS to GAE/J ( jdo, join, sql )

[K.Honsali]

I would have added
d) use an embedded rdbms, and do own consistency

If there was a way to control running instances like in EC2



On Nov 25, 5:17 pm, "K.Honsali"  wrote:
> Hi all,
>
> If my understanding of previous discussions is correct, we can resume
> from:
> - GAE/J is not relational (not full JDO too), and hence does not
> support sql features such as joins, like, not in ...etc
> - the solution is to de-normalize your tables ... or your mind..
>
> Now, suppose you have a quite big classic sql-based webapp which is
> multi-layered like a burger, so it is OK to change the Data Access
> Layer without affecting the other components, provided that the DAL
> calls and outputs remain the same.
> If you want to migrate this app to GAE/J, how would you do; knowing
> that beside CRUD queries, you have queries that execute (on the fly w/
> sql) up to a dozen joins ?
> a )  re-write your DAL in GAE/J's JDO, by denormalizing your tables (&
> your mind)
> b )  write your own sql wrapper, using full JDO and the low level
> datastore (can it be?)
> c )  none of the above
>
> Thanks for your CPU time :)

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[appengine-java] Re: on switching a webapp from RDBMS to GAE/J ( jdo, join, sql )

[Roy]

I have an ant task which will reverse engineer a database and create a
GAE LLAPI DAL.
Eg if your database is dept Hi all,
>
> If my understanding of previous discussions is correct, we can resume
> from:
> - GAE/J is not relational (not full JDO too), and hence does not
> support sql features such as joins, like, not in ...etc
> - the solution is to de-normalize your tables ... or your mind..
>
> Now, suppose you have a quite big classic sql-based webapp which is
> multi-layered like a burger, so it is OK to change the Data Access
> Layer without affecting the other components, provided that the DAL
> calls and outputs remain the same.
> If you want to migrate this app to GAE/J, how would you do; knowing
> that beside CRUD queries, you have queries that execute (on the fly w/
> sql) up to a dozen joins ?
> a )  re-write your DAL in GAE/J's JDO, by denormalizing your tables (&
> your mind)
> b )  write your own sql wrapper, using full JDO and the low level
> datastore (can it be?)
> c )  none of the above
>
> Thanks for your CPU time :)

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[appengine-java] Re: on switching a webapp from RDBMS to GAE/J ( jdo, join, sql )

[vbart]

I tried to create a DAO generator which will generate code for GAE/J.
I started on my existing solution for classical RDBMS. Now it works
for all simple CRUD tasks and also it supports relations. So now it is
possible to generate an application's DAO layer for MySQL or Oracle
and also for GAE.

Of course, if you use complicated SQLs - joins, nested SQLs - there is
no simple solution to migrate. But for applications which only use
find/update/delete operations based on primary keys and indexes you
can fully rely on the automatic DAO generator.
If you are interested in, please visit http://audao.spoledge.com

Regards
Vaclav

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Re: [appengine-java] Re: on switching a webapp from RDBMS to GAE/J ( jdo, join, sql )

[Ikai L (Google)]

Your first option is what we recommend. App Engine's data model is similar
to that of a federated data model based on sharded relational databases.
Here's a pretty good session from Google I/O 2009 about migrating to/from
RDBMS:

http://code.google.com/events/io/2009/sessions/SofterSideofSchemas.html

On Wed, Nov 25, 2009 at 9:40 AM, K.Honsali  wrote:

> I would have added
> d) use an embedded rdbms, and do own consistency
>
> If there was a way to control running instances like in EC2
>
>
>
> On Nov 25, 5:17 pm, "K.Honsali"  wrote:
> > Hi all,
> >
> > If my understanding of previous discussions is correct, we can resume
> > from:
> > - GAE/J is not relational (not full JDO too), and hence does not
> > support sql features such as joins, like, not in ...etc
> > - the solution is to de-normalize your tables ... or your mind..
> >
> > Now, suppose you have a quite big classic sql-based webapp which is
> > multi-layered like a burger, so it is OK to change the Data Access
> > Layer without affecting the other components, provided that the DAL
> > calls and outputs remain the same.
> > If you want to migrate this app to GAE/J, how would you do; knowing
> > that beside CRUD queries, you have queries that execute (on the fly w/
> > sql) up to a dozen joins ?
> > a )  re-write your DAL in GAE/J's JDO, by denormalizing your tables (&
> > your mind)
> > b )  write your own sql wrapper, using full JDO and the low level
> > datastore (can it be?)
> > c )  none of the above
> >
> > Thanks for your CPU time :)
>
> --
>
> You received this message because you are subscribed to the Google Groups
> "Google App Engine for Java" group.
> To post to this group, send email to
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> .
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> http://groups.google.com/group/google-appengine-java?hl=en.
>
>
>


-- 
Ikai Lan
Developer Programs Engineer, Google App Engine

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