dhis2-devs team mailing list archive

[Lars Helge Øverland <larshelge@xxxxxxxxx>]

I have looked at different alternatives for the embedded database in the
lite version.

- H2 is not working out so well. It seems the Hibernate H2Dialect is buggy.
The H2 people tried to submit a patch but it didn't work so well. It's all
explained here:
http://opensource.atlassian.com/projects/hibernate/browse/HHH-3401 .

What is weird is that all our unit tests run fine on H2 but I guess we
haven't covered it all. I get problems e.g. on import for calculated data
elements, which is mapped as a subclass of DataElement in Hibernate.

- Derby embedded looks as a good alternative, but unfortunately crashes at
database creation time because "indicator" and "translation" (which are
database table names in DHIS 2) are reserved words in Derby (doh). I don't
feel like starting to rename the tables, any other suggestions?

- HSQLDB works fine with Hibernate, but the current 1.8 version does not
support the multiple insert SQL syntax, which is used heavily in the import
and datamart process. According to the roadmap this will be supported in the
1.9 version. The 1.9 Alpha 2 version was released on April 1, but it is not
present in the maven repo and we shouldn't base ourselves on an alpha. Also,
I don't feel like going for this one after reading this:

"SQLDB has two main table types used for durable read-write data storage.
The default MEMORY type stores all data changes to the disk in the form of a
SQL script. During engine start up, these commands are executed and data is
reconstructed into the memory. While this behavior is not suitable for very
large tables, it provides highly regarded performance benefits and is easy
to debug."

Please help...