Feature summary
In miser mode, Special:UnreviewedPages only shows at most 5000 unreviewed pages. Currently, the cache is shared between namespaces (even though the special page itself forces the user to select a namespace, so it’s impossible to show unreviewed pages from all namespaces at once), which means that if a namespace contains more than 5000 unreviewed pages, it may cause all other namespaces’ lists to be empty, even if those namespaces also have unreviewed pages. The cache should be modified to contain pages from all namespaces that have unreviewed pages.
The easiest solution is to simply query at most 5000 pages from each flagged namespace, and concatenate them. This could in edge case multiply the query page cache’s size by the number of flagged namespaces, but since this is quite an edge case, the multiplier is still a constant (implicitly) set in LocalSettings.php, and the 5000 seems to be arbitrary value anyways, I don’t think it would cause issues.
Use cases
Using Special:UnreviewedPages in wikis that have a very large number of unreviewed pages. Several bug reports (T300970, T307857, T309429) could hopefully be resolved by this feature.
Benefits
Reviewing in different namespaces require different attitudes. If someone specializes on reviewing files or templates, they won’t be prevented by unreviewed pages in namespaces they don’t want to review.