XWiki#getClassList() is very slow on large instances - object editor takes a long time to load on large instances

The function to fetch all XClasses of XWiki is using the following query, which is very slow on large XWiki instances:

select doc.fullName from XWikiDocument as doc where (doc.xWikiClassXML is not null and doc.xWikiClassXML like '<%')

This function is called when loading the object editor, for displaying the new object form. On large instances, this function is very slow which makes the loading of the object editor very slow for any document, regardless of the number of objects of the document in question.

The field xWikiClassXML in the documents table is not indexed, a manual index on this field may be a workaround.