https://bugzilla.wikimedia.org/show_bug.cgi?id=26393
Summary: Make page_len index actually useful so
Special:Longpages and Special:Shortpages will be
efficient
Product: MediaWiki
Version: 1.18-svn
Platform: All
OS/Version: All
Status: NEW
Severity: enhancement
Priority: Normal
Component: Database
AssignedTo: wikibugs-l@lists.wikimedia.org
ReportedBy: roan.katt...@gmail.com
Presumably in an attempt to optimize Special:(Long|Short)pages, a page_len
index was introduced in version 1.5 (according to a comment I found). However,
because the query these special pages do is something like SELECT stuff FROM
page WHERE page_namespace IN (content namespaces) AND page_is_redirect=0 ORDER
BY page_len (ASC|DESC) , an index on page_len alone doesn't suffice.
For Longpages it's arguably good enough, since the WHERE clause is gonna be
true for almost all of the 50/100/500/whatever longest pages. For Shortpages,
however, the opposite is true.
In order to fix this properly, we'd have to extend the index of (page_len) to
cover (page_len, page_is_redirect, ppage_namespace) so the WHERE clause is
fully indexed. Any existing legitimate uses of the page_len index (are there
any?) will continue to work because page_len will still be the first field in
the index.
I'll attach a patch shortly.
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