4 Oct
2011
4 Oct
'11
5:10 p.m.
Hi devs,
I need to do XWIKI-6990 (Reduce the likelihood of having same (hibernate)
document id for different documents), but XWIKI-7006 (Accessing a store that
is not migrated to the lastest data version should not be allowed) is
blocking for this to be safely introduced.
So I have refactored the migration code to better protect the database, I
would like your vote to introduce this patch first, another vote will come
for XWIKI-6990.
The proposed commit is available at
https://github.com/dgervalle/xwiki-platform/commit/f1fa1b1357d17c1ee4ed65eb…
In summary, here is what it does:
a) Refactor the old XWikiMigrationInterface and XWikiMigratorInterface into
new DataMigrationManager and DataMigration interfaces
b) Implement the DataMigrationManager and the DataMigration interfaces
using components for the hibernate stores
c) Remove the migration check from XWiki and put them in hibernate stores
components, freeing this from XWiki. Since store still use the XWikiContext,
I still use it, but from the execution context, no more passing it
everywhere.
d) Use a cache for DB version to not degrade performance
e) Remove many call to schemaUpdate which require synchronization,
executing only schema updates during data migrations.
f) Remove some data migration like code from schemaUpdate, convert it to
HQL (in place of native SQL :() and put them in an initial
LegacyDataMigration, that migrate from version 0 to version 1
g) Fix empty/new database issue by considering a database without version
AND without documents as a new database, and initialize it with the current
schema and the latest version.
h) Properly report migration failure and prevent access on failure
i) Prevent access to any database not being properly migrated to the latest
version by never providing a valid transaction for it. By the way, fix
another (unnoticed ?) bug: if a throw occurs during database switching, a
transaction could be return and used improperly (mixing data from different
database).
j) deprecate xwiki.store.hibernate.updateschema, but
use "1".equals(config.getProperty("xwiki.store.migration",
"0") &&
!"0".equals(config.getProperty("xwiki.store.hibernate.updateschema")
to
enable migrations
k) Now xwiki.store.migration.databases=all, before it was xwiki only, which
is not right IMO
Currently, migration manager is injected in stores, using a hint, since the
migration manager will be different depending on the store that keep the
data version. The migration manager lookup the store by hint to retrieve the
data version. The migration manager lookup data migrations using hint as
well. Finally, data migrations lookup stores again using hint.
Some improvements would be to allow multiple data versions (one per store
hint), and mix data migration, since stores could be mixed, but this is out
of my scope currently.
To support injecting store by scope properly, there is another separate
commit, available at
https://github.com/dgervalle/xwiki-platform/commit/6a353d6d45bfb73789ed0693…,
which replace the default unnamed stores, by "hibernate" named stores.
Since store are still initialized at XWiki initialization, migration still
occurs during first request to the system, but this is no more related to
the migration system, which intercept the first database access, but this is
related to this XWiki initialization only now. So XWIKI-2075 is fixed for
me.
I have already work hard to reach this state, there is still room for
improvements, but I will not be able to afford much more time on this right
now (at least without a sponsor :)). Please be fair in your remarks ;)
Here is my +1. Currently the patch is done for 3.3, but if you think it
could go in 3.2, I am +1.
--
Denis Gervalle
SOFTEC sa - CEO
eGuilde sarl - CTO