Help:Database layout

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Most data for the wiki is stored in a database. See MySQL config for setup info.

(Some data lives only in the filesystem, other data is just cached there. Data may also be cached in memcached, but lives permanently in the database.)

NB: the current schema for any version - with copious comments - can be found in the maintenance/tables.sql file. The latest version can be obtained from CVS.

docs/schema.txt may also contain some hints.

Version 1.4 uses the following tables:

• archive table - "deleted" pages
• blobs table
• brokenlinks table - links in internal link style to non-existing pages in the same project (see below)
• categorylinks table
• cur table - current pages
• hitcounter table
• image table
• imagelinks table tracks usage of images in wikipages (see below)
• interwiki table
• ipblocks table
• links table - links in internal link style to existing pages in the same project (see below)
• linkscc table - (see below)
• math table
• objectcache table
• old table - old versions of pages
• oldimage table
• querycache table
• recentchanges table
• searchindex table
• site_stats table
• testac table
• user table
• user_newtalk table
• watchlist table

Explanation of the link tables

There are presently three link tables: links, brokenlinks and imagelinks. There are a couple of uses for these tables:

• enables "What links here" and "Related changes" to work, looking at incoming or outgoing links
• provides the list of pages that use an image shown on an image's description page
• allows making reports of pages that aren't linked (Orphans, Unused images) or are linked to but don't exist (Most wanted pages)
• slightly speed up page rendering by avoiding individual checks for the existence of each linked page to determine how to render its link

The latest software also adds a 'linkscc' table which caches data from the other three tables. This is used only for speeding rendering.

Maintenance of link tables

If you import data to the cur table and don't rebuild the links, you won't be able to use "What links here", "Related changes", "Orphans".

See also

• m:Experimental new database schema 22:55, 24 Jul 2003
• m:Proposed Database Schema Changes 18:19, 23 Dec 2003
• w:en:Wikipedia:Database queries
• w:nl:Wikipedia:SQL opdrachten
• m:Documentation: Developer's Guide