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Re: [eclipselink-users] Dynamic DDL_GENERATION and execution at database
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Hi Markus,
The EclipseLink DDL generation feature does not do any checks to see if the
tables exist. It simply tries to execute the SQL and reports any exceptions to you.
If the tables potentially already exist, you can do one of the following:
- Set the eclipselink.ddl-generation to drop-and-create-tables. This will
execute drop statements before the create statements
- Write some logic of your own that makes use of the following:
- The eclipselink.ddl-generation property can be provided in the map of
arguments to createEntityManagerFactory(String, Map) and therefore you can
decide (potentially based on an exception) whether to use it.
- EclipseLink can be instructed to produce text files with the SQL instead.
These files can then be used by your application. To do that, use the
eclipselink.ddl-generation.output-mode property and set it to "sql-script" and
set eclipselink.create-ddl-jdbc-file-name and
eclipselink.drop-ddl-jdbc-file-name to point to the location the files should be
generated to.
-Tom
Markus Kolb wrote:
Hi,
I've some questions to the automatic DDL generation and execution at
database.
As it seems the DDL statements are checked with database layout at first
connection after application startup.
If the tables doesn't exist in DB they are created as it is supposed to be.
If the tables already exist and the application is restarted there is
always an ugly exception message in eclipselink log that the tables
already exist.
First I've thought it is possible to check the DB first with an SELECT.
On Exception I wanted to use another EntityManagerFactory, with enabled
DDL_GENERATION property set, to create the tables.
But then the DDL_GENERATION is not enabled during first connection to DB
after application start and there won't be created any tables.
Do you know any solution for this?
Is this DDL_GENERATION limitation on _first_ connection like it ought to
be, do I anything wrong or is it a bug?
Thanks
Markus
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