Wikipedia:Purge
From Wikipedia, the free encyclopedia.
The purge function is a handy way to clear a page's server cache. This forces the wiki software to rebuild the page completely.
Some pages use transclusion to incorporate subpages or templates. If you can't see the transcluded pages properly, purging might help.
We have a handy template which creates a clickable link that performs the purge: {{purge}}. All you have to do is add something like {{purge|Purge this page's server cache}} to the page.
For those who care how it works
When a change is made to a page, the MediaWiki software saves the change to the main database. The next time a non-logged in user views the page, a copy of that page is made to a "server cache" on a set of secondary servers. Until the page is changed again, all non-logged in users who try to view that page will be shown the copy from the server cache. That way, users who are viewing but not editing do not put a drain on the main database server, and still see the most recent version of the page. (Logged-in users have a choice in their Special:preferences whether to see cached or live versions.)
Normally, when a change is made, the page is marked as "touched" and the software will create a new copy of the page for the server cache. However, when a change is made to a subpage or template, but not to the article page which transcludes it, the article page is not marked as "touched", and a new copy is not generated for the cache. Therefore anyone viewing the article page may see a cached page which includes old versions of the subpage or template.
The purge command is a URL which includes the text "&action=purge", which forces the server cache to purge the old version of the page. The next time the page is viewed, the page will be rebuilt from scratch, including fresh versions of all subpages and templates, and a new copy will be made for the server cache.
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