Deleting and recreating a subwiki does not work (throws exception)

To reproduce, in a multiwiki instance:

• create a subwiki (I used WikiManager.CreateNewWiki but I don't think workspaces changes anything)
• delete it
• re-create the same subwiki: you won't be able to complete, you'll get an error.
  The exception is something like this

  La création du wiki "wikitemplate" a échoué : Error number 50035 in 5: Exception in plugin xpn.xwiki.plugin.wikimanager.Wiki Manager Plugin?: Wiki wikitemplate? database update failed Wrapped Exception: Error number 3202 in 3: Exception while reading document name = [XWiki Preferences?, type = DOCUMENT?, parent = name = [XWiki?, type = SPACE?, parent = name = [wikitemplate?, type = WIKI?, parent = null?]]] Wrapped Exception: could not load an entity: xpn.xwiki.doc.XWiki Document?.
  

  and in the logs there is something like this

  2012-04-30 15:42:11,057 [http://localhost:8080/xwiki/bin/view/WikiManager/CreateNewWiki?wikiname=wikitemplate&XWiki.XWikiServerClass_0_wikiprettyname=Wikitemplate&XWiki.XWikiServerClass_0_description=Template+de+wiki&XWiki.XWikiServerClass_0_server=wikitemplate&XWiki.XWikiServerClass_0_owner=XWiki.Admin&XWiki.XWikiServerClass_0_owner=&form_token=xzmqd1ltxjjhsN56v4ccLw&actioncreate=Cr%C3%A9er] ERROR o.h.u.JDBCExceptionReporter    - Table 'wikitemplate.xwikidoc' doesn't exist 
  

This is caused because the subwiki database schema is not initialized, so initializeXWikiClasses() which is done upon creation of the subwiki, is trying to get a table which doesn't exist.

The reason for which the subwiki schema is not initialized is because, in the function

com.xpn.xwiki.store.migration.AbstractDataMigrationManager.checkDatabase()

, where a new database should be initialized, the newly re-created wiki fails to be seen as new database, because of the database version cache. The function com.xpn.xwiki.store.migration.AbstractDataMigrationManager.getDBVersion() will get the version of the wikitemplate database from the cache, and will think it's great and up to date. The fix would be to clear this cache when a subwiki is deleted.

Note that, of course, since this it's a cache issue, a server restart between the delete and the re-create will work perfectly fine as a workaround.