The spaces panel is blocking loading of the panels admin on very large instances

The Spaces panel is a pretty old panel, what it does is essentially display a list of all the spaces registered in the database to which the user has access to.

This list is displayed without any pagination. While this is already an issue for large instances that use the panel, this has also an impact on the panel administration page of every XWiki instance that have a very high number of spaces.

In the panel admin, every panel gets rendered to allow for drag and drop. When the spaces panel is rendered, this will generate a high load on the server, which sometimes can make the request to XWiki time out.

I see two potential options to solve this issue :

• We could get rid completely of the spaces panel, which has been deprecated for quite a while now
• Or we could also re-write it to use paginated queries