The new template inclusion tracking code is now live. Here's the description of it from RELEASE-NOTES in case you missed it:
* Added templatelinks table, to track template inclusions. User-visible effects will be: * (inclusion) tag for inclusions in Special:Whatlinkshere * More accurate list of used templates on the edit page * More reliable cache invalidation when templates outside the template namespace are changed
There were a few teething problems when it was introduced. The following are now fixed: * Random fatal errors from OutputPage.php line 230, BoardVote.php line 6 and LinksUpdate line 158 due to sync problems on srv11, srv50 and some other server. Root cause unclear. * Save and some other functions broken on yaseo wikis (ja, th, ms and ko wikipedia), forgot to apply schema update. * Missing page list from category pages, due to index.php being pinned at version 1.111 in the live copy. * Missing or broken category list on image pages, redirects and preview pages, bug. * Undelete broken, bug. * Special:Whatlinkshere for certain templates showing only half the requested number of pages, bug.
Please mark any related bug reports (on or off bugzilla) as resolved, unless they can be reproduced at the present time.
The (inclusion) tag in [[Special:Whatlinkshere]] is currently based on whether the target page is in the template namespace or not. This will progressively be fixed over the next week or so, as refreshLinks.php works its way through several million articles.
Here's the more technically-oriented commit message describing my changes:
* Added templatelinks table. The table currently represents a literal list of templates included from each article. That is, the table contains pages which were actually loaded during parsing, not the markup which went into resolving their names. * Ended the role of $wgLinkCache in link updates. Instead, links (and related entities) are registered in the ParserOutput object during a parse. The LinksUpdate constructor now takes a ParserOutput object as a parameter. $wgLinkCache is still used, but only as a cache of article IDs. * Because the link list is now saved and restored in the parser cache, meta tag keywords now work on parser cache hits. Some refactoring took place in this area. * Rendering of the HTML for category links has moved from Parser to OutputPage. * Did some general pottering around in Article.php, such as allowing an Article object to be created with a specified revision ID, thereby optionally removing the dependence on $wgRequest. Not used at the current time. * A few documentation tweaks.
-- Tim Starling