[Wikia-l] Category tree

[Laurence Parry]

> Re Wikipedia: Conceivably they could disable a feature such as this due to 
> their
> enormous and fast-changing categories (I imagine the feature would have a
> performance hit).

I understand they made a special Category table just to track this 
information so that it wouldn't be too expensive. From the trunk database 
schema:

-- Track all existing categories.  Something is a category if 1) it has an 
en-
-- try somewhere in categorylinks, or 2) it once did.  Categories might not
-- have corresponding pages, so they need to be tracked separately.
--
CREATE TABLE /*$wgDBprefix*/category (
  -- Primary key
  cat_id int unsigned NOT NULL auto_increment,

  -- Name of the category, in the same form as page_title (with 
underscores).
  -- If there is a category page corresponding to this category, by 
definition,
  -- it has this name (in the Category namespace).
  cat_title varchar(255) binary NOT NULL,

  -- The numbers of member pages (including categories and media), 
subcatego-
  -- ries, and Image: namespace members, respectively.  These are signed to
  -- make underflow more obvious.  We make the first number include the 
second
  -- two for better sorting: subtracting for display is easy, adding for 
order-
  -- ing is not.
  cat_pages int signed NOT NULL default 0,
  cat_subcats int signed NOT NULL default 0,
  cat_files int signed NOT NULL default 0,

  -- Reserved for future use
  cat_hidden tinyint unsigned NOT NULL default 0,

  PRIMARY KEY (cat_id),
  UNIQUE KEY (cat_title),

  -- For Special:Mostlinkedcategories
  KEY (cat_pages)
) /*$wgDBTableOptions*/;


-- 
Laurence "GreenReaper" Parry
http://greenreaper.co.uk/ - http://wikifur.com/
"Eternity lies ahead of us, and behind. Have you drunk your fill?"