We explicitly do not support it yet, but we could probably attempt to make it work in most cases.
https://github.com/xwiki-contrib/cql/blob/33f54fda6201439baeecad325a5f011255daf436/query/src/test/java/org/xwiki/contrib/cql/query/CQLTest.java#L297-L302
https://developer.atlassian.com/server/confluence/advanced-searching-using-cql/#space-title
