empire-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Eike Kettner <n...@eknet.org>
Subject Re: how to add a "foreign" table
Date Sun, 14 Feb 2010 16:38:54 GMT
Hi Rainer

thank you for your quick response; and you're very welcome with this 
spring example, I'm glad if can help.

My final goal was to create some kind of migration script to upgrade my 
db schema, because my app will contain some new features in next 
versions which will add tables and columns to the existing db schema. I 
want to compare two instances of DBDatabase and generate the sql ddl 
statements. So actually, I don't really need to add the table to the 
other db, but I want to create arbitary sql ddl statements (for DBTable, 
DBColumn, DBView...) using a different driver. This works with DBDatabse 
already, I can specify a DBDatabaseDriver there and the method will 
change the driver temporarily. Therefor I tried to either add the 
missing table from the one db to the other or to set the 
DBDatabaseDriver of the first db into the second, so I can use the 
second DB to create its table - but now with the driver from the first db...

I somehow got an evil workaround by serializing the two DBDatabses and 
while deserializing back, I inject my desired driver into the 
DBDatabases. So I end up with a clone of the db having my target driver 
attached.

Thank you four your help!
Eike

Rainer Döbele wrote:
> Hi Eike,
>
> first I want to thank you very much for your submission of the spring example.
> Unfortunately I did not have the chance to look at it so far - but I am quite keen to
do so.
> I'll let you know when I have.
>
> Now about your question:
> A DBTable object may only belong to one database object just like an XMLElement belongs
to its XMLDocument.
> This assignment is usually performed on creation of the DBTable and there is no mechanism
to change it.
>
> Hence if you really need to need a copy of the table object of one database in another
one you need to create a new instance of the table object.
> Normally you would just create a instalce of the table like this:
>
>     DBTable t = new DB1.SomeTable(db2);
>
> If your code should be more generic then you might use something like:
>
>     DBTable t = db1.getTable(...);
>     t.getClass().getConstructor(DBDatabase.class).newInstance(new Object[] { db2 });
>
> This assumes that the table has a constructor that takes the db as a parameter.
>
> Hope this is what you need.
> Otherwiese I would need to know what excatly you are trying to achieve with this.
>
> Regards
> Rainer
>
>
> Eike Kettner wrote:
>   
>> re: how to add a "foreign" table
>>
>> Hello all,
>>
>> I'm facing a problem that I want to add a table from one db to another
>> db. I have two DBDatabases and I like to add a table from DB1 to DB2,
>> something like this:
>>
>>
>>   DBDatabase db1 = ..
>>   DBDatabase db2 = ..
>>
>>   DBTable table1 = db1.getTable(0);
>>
>>   db2.addTable(table1);
>>
>>
>> actually, what i want is to create a table on DB2 that is present on
>> DB1, without too much coding ;-)
>>
>> Thankful for any help!
>>
>> Kind regards,
>> Eike
>>     
>
>   


Mime
View raw message