Question

I recently used Wikipedia’s function “What links here” (which is found under the “Toolbox” element in any entry’s left menu) and it got me started wondering how this function actually works.
I’m guessing that searching through all the article entries after links isn’t very effective, so are all the links stored in a separate database? If so, is this updated when an article is edited or another time?

Thanks.

Answer 1

Whenever a page on Wikipedia is edited, it is placed into a background queue that does some further processing. Some of the things that happen there are:

• updates to the “what links here” for other pages
• updates to category index pages
• updates to the global cache of existing pages to help render “redlinks” on other pages

This sort of information doesn’t need to be updated right away when you hit “Submit”, so the background processing queue takes care of it. Sometimes this queue can grow quite large, but usually it’s kept under control.

You can find more information about this at Help:Job Queue.