[news.eclipse.rt.eclipselink] Re: How to upgrade database schema built w

[Enrico <enrico.balatti@xxxxxxxxx>]

Yes, you are right.
I don't know if there is a solution for that without write specific sql 
scritps.
I am too interested to know if there is something better.
Hope to have some reply from the community.

BR,
Enrico

Markus Zander ha scritto:
> Hi Enrico,
>
> yes, I mean "update my schema". Your Idea is good for new tables. But 
> what, if I have to add a new field or key or if I have to split an 
> entity in two?
>
> Here a very simple example:
>
>
>
> Old version:
> Entity "Student"
> Attributes: Name, Registration No., Adress, Phone
>
>
>
> New version:
> Entity "Student"
> Attributes: Sure Name, Given Name, Registration No., Street, City, Zip Code
>
> Entity "Phone_Numbers"
> Attribtutes: Registration No. (as foreign key), Phone type, Phone
>
>
>
>
> How can I convert an existing database from "old version" to "new 
> version" without having database platform specific SQL statements?
>
> Markus
>
>
>
>
> Enrico schrieb:
> > Hi MArkus,
> >
> > I am not sure what do you mean with upgrade...d you mean update your 
> > schema?If so, what about to use:
> >
> > <property name="eclipselink.ddl-generation" value="create-tables" />
> > <property name="eclipselink.ddl-generation.output-mode" 
> > value="database"/>
> >
> >
> > in your persitence.xml file.
> >
> > This will generate schema when you run your application, basing on 
> > properties of your entities (if table). As options you can have:
> >
> > *  none â EclipseLink does not generate DDL; no schema is generated.
> > * create-tables â EclipseLink will attempt to execute a CREATE TABLE 
> > SQL for each table. If the table already exists, EclipseLink will 
> > follow the default behavior of your specific database and JDBC driver 
> > combination (when a CREATE TABLE SQL is issued for an already existing 
> > table). In most cases an exception is thrown and the table is not 
> > created. EclipseLink will then continue with the next statement. (See 
> > also eclipselink.create-ddl-jdbc-file-name.)
> > * drop-and-create-tables â EclipseLink will attempt to DROP all 
> > tables, then CREATE all tables. If any issues are encountered, 
> > EclipseLink will follow the default behavior of your specific database 
> > and JDBC driver combination, then continue with the next statement. 
> > (See also eclipselink.create-ddl-jdbc-file-name and 
> > eclipselink.drop-ddl-jdbc-file-name.)
> >
> > BR,
> > Enrico
> >
> >
> >
> > Markus Zander ha scritto:
> > > Hi,
> > >
> > > I'm looking for a general solution for upgrading database schema 
> > > built with EclipseLink. How do you do it in your projects?
> > >
> > > The first solution that comes to my mind is to create my own 
> > > mechanism for upgrading databases, with SQL scripts doing all the 
> > > work. But in this case I'll have to remember about creating new 
> > > scripts every time the object mappings are updated. And I'll still 
> > > have to deal with low-level SQL queries, instead of just defining 
> > > mappings and allowing the ORM tools to do all the job...
> > >
> > > So the question is how to do it properly. Maybe some tools allow for 
> > > simplifying this task (for example, I heard that Rails have such 
> > > mechanism built-in).
> > >
> > > Thanks for any suggestions.
> > >
> > > Markus