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Re: two different databases at same time?
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Re: two different databases at same time?

  • Subject: Re: two different databases at same time?
  • From: "Cheong Hee (Gmail)" <email@hidden>
  • Date: Fri, 6 Aug 2010 17:53:57 +0800
Could it be something else that is the culprit? If you think worth to cross examine, let me know so that I could repackage the test files into eclipse project and send over.

----- Original Message ----- From: "Cheong Hee (Gmail)" <email@hidden>
To: "Joe Little" <email@hidden>
Cc: "David LeBer" <email@hidden>; "WO Dev Group" <email@hidden>
Sent: Friday, August 06, 2010 3:09 PM
Subject: Re: two different databases at same time?


It should be quite straight forward. To show it works, I have just tested with 2 model, each point to their own db. It works as expected :)
The testing environment however is mysql, and wo5.2.4, with plain vanila without PW. Don't think it is matter for test.

Just to add, the database url are defined in each model.

Cheers

Cheong Hee

----- Original Message ----- From: "Joe Little" <email@hidden>
To: "Cheong Hee (Gmail)" <email@hidden>
Cc: "David LeBer" <email@hidden>; "WO Dev Group" <email@hidden>
Sent: Friday, August 06, 2010 1:07 PM
Subject: Re: two different databases at same time?


I just checked and my models do indeed have a complete URL, etc in
their default connection dictionaries.


On Thu, Aug 5, 2010 at 7:57 PM, Cheong Hee (Gmail) <email@hidden> wrote:
Will there make any difference if these connection dictionaries is defined
in respective model db url?

----- Original Message ----- From: "Joe Little" <email@hidden>
To: "Joe Little" <email@hidden>
Cc: "Cheong Hee (Gmail)" <email@hidden>; "David LeBer"
<email@hidden>; "WO Dev Group"
<email@hidden>
Sent: Friday, August 06, 2010 2:17 AM
Subject: Re: two different databases at same time?


So, I'm starting to wonder if something broke/changed in Wonder. I've set up
test projects that list two DBs in the Properties file for two models, but
only one is ever added to the connection dictionary. Does there need to
workable values for the default database in the eomodeld directory itself?

This has worked for me before, with one framework model and one local
project model. This time, i have two models in one framework.


On Aug 4, 2010, at 7:26 PM, Joe Little <email@hidden> wrote:

You gave me a good clue. I may be using the same damn ec

On Aug 4, 2010, at 7:17 PM, "Cheong Hee \(Gmail\)" <email@hidden>
wrote:

When the question posted, I intended to find out if the different db
works in the same ec. I have not thought more on the storing and fetching.

I am not sure if this is right but merely bring it out for better
understanding. Please point out whichever does not seem right:

Said the Student table is in databaase A. The AdmitApplicant table is
stored in database B.
A row admitApplicantID is created in Student table and a relationship
should be defined, said admitApplicant. The modelling cross different
database should be fine.

If I understand what David mentioned, the EOF fetch through relationship
admitApplicant will fail. Therefore, I will assume that the fetch will have
to be done by getting the admitApplicant key from Student, and then use the
key to search the AdmitApplicant that is resided in database B. Good thing
is both could be done in the same ec.

Cheers

Cheong Hee

----- Original Message ----- From: "David LeBer"
<email@hidden>
To: "Joe Little" <email@hidden>
Cc: "Cheong Hee" <email@hidden>; "WO Dev Group"
<email@hidden>
Sent: Thursday, August 05, 2010 2:36 AM
Subject: Re: two different databases at same time?



On 2010-08-04, at 2:26 PM, Joe Little wrote:

On Wed, Aug 4, 2010 at 11:20 AM, David LeBer
<email@hidden> wrote:


On 2010-08-04, at 2:12 PM, Joe Little wrote:

Digging up an old thread. This is the first time I'm creating a
multi-database relation. When my migrations kick off to generate my
newer database that has a single relation to the old, it fails in
spectacular ways.

Specifically, it has this error:

Caused by: java.lang.RuntimeException: Failed to execute 'ALTER TABLE
STUDENT ADD CONSTRAINT STUDENT_admitApplicantID_ID_FK FOREIGN KEY
(admitApplicantID) REFERENCES ADMIT_APPLICANT (ID) DEFERRABLE
INITIALLY DEFERRED'.
PSQLException: ERROR: relation "admit_applicant" does not exist

student has a relation to admit_applicant, where student is
db2.student and admit_applicant is db1.admit_applicant

This is keyed off this migration line:

studentTable.addForeignKey("admitApplicantID", "ADMIT_APPLICANT",
"ID");


Don't do that.

EOF is fine with cross database relationships but your DB probably
isn't. So it won't like you trying to create a foreign key constraint to a
different database, so don't. 

So, what is the alternative? Would a join table work -- I think that
still has foreign key constraints. Or is it simply stating a differ
type of join (not inner)? I haven't done this before so my lack of
clue is telling.

Sorry, I wasn't clear. Model the relationship in the EOModel, create a
vanilla row in the db that will act as a foreign key for the relationship,
but don't tell the db that it is a foreign key. Let EOF manage the
relationship for you.




Am I just missing some clue that others already have?

On Thu, Apr 1, 2010 at 8:17 PM, Cheong Hee <email@hidden> wrote: 

Apparently I have complicated it by thinking of using multi ec to
handle
respective database connections. Thanks for clarification..

Cheers

Cheong Hee

----- Original Message ----- From: "David LeBer"
<email@hidden>
To: "Cheong Hee" <email@hidden>
Cc: "WO Dev Group" <email@hidden>
Sent: Thursday, April 01, 2010 8:23 PM
Subject: Re: two different databases at same time?



On 2010-04-01, at 12:07 AM, Cheong Hee wrote:

Is there any pointers or sample code how these could be done to
initiate
connection and save changes in respective ec?


You don't need multiple ec's unless you want them. Other than that
it's
transparent.

EOEditingContext ec = ERXEC.newEditingContext();
Person p = (Person)EOUtitlites.createAndInsertInstance(ec,
Person.ENTITY_NAME); // Person entity persists in database A
Horse h = (Horse)EOUtitlites.createAndInsertInstance(ec,
Horse.ENTITY_NAME);
// Horse entity persists in database B
// make chagnes to h and p
ec.saveChanges(); // p saved to database A, h saved to database B

You can model cross database relationships as long as you don't try
and
create a fetch based on them.


Cheers

Cheong Hee

----- Original Message ----- From: "Mark Ritchie"
<email@hidden>
To: "James Cicenia" <email@hidden>
Cc: "WO Dev Group" <email@hidden>
Sent: Thursday, April 01, 2010 1:05 AM
Subject: Re: two different databases at same time?


On 31/Mar/2010, at 8:15 AM, James Cicenia wrote: 

Is it possible to use two different databases, I guess via two
different
models?
I will need to connect to an Oracle big database on a remote
server and
was
wondering if I could also use a mySQL or postgres database for
user
control
on local server.


Yes, yes! You can have multiple concurrent connections! One for
each
EOModel!
Just make sure that the entity names are unique across all
EOModels!
Good luck!
M.
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;david

--
David LeBer
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;david

--
David LeBer
Codeferous Software
'co-def-er-ous' adj. Literally 'code-bearing'
site: http://codeferous.com
blog: http://davidleber.net
profile: http://www.linkedin.com/in/davidleber
twitter: http://twitter.com/rebeld
--
Toronto Area Cocoa / WebObjects developers group:
http://tacow.org






;david

--
David LeBer
Codeferous Software
'co-def-er-ous' adj. Literally 'code-bearing'
site: http://codeferous.com
blog: http://davidleber.net
profile: http://www.linkedin.com/in/davidleber
twitter: http://twitter.com/rebeld
--
Toronto Area Cocoa / WebObjects developers group:
http://tacow.org









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