Fresh 1.11 wiki installations have interwiki.sql loaded by
default. Installations upgrading to 1.11 do not get it loaded.

Let's take a peek into the future. Perhaps around version 1.15.

People who starting using MediaWiki after around 1.11 will be
enjoying interwiki linking, while those who started earlier will be
scratching their heads, even though both dutifully do regular updates.

We examine the cause:

This part of updaters.inc is good intentioned,

function do_interwiki_update() {
        # Check that interwiki table exists; if it doesn't source it
        global $wgDatabase, $IP;
        if( $wgDatabase->tableExists( "interwiki" ) ) {
                echo "...already have interwiki table\n";
                return true;
        }
        echo "Creating interwiki table: ";
        dbsource( archive("patch-interwiki.sql") );
        echo "ok\n";
        echo "Adding default interwiki definitions: ";
        dbsource( "$IP/maintenance/interwiki.sql" );
        echo "ok\n";
}

However, as this dump of the post update database shows,

• Table structure for table wiki_interwiki --
  
  DROP TABLE IF EXISTS wiki_interwiki; CREATE TABLE wiki_interwiki ( iw_prefix char(32) NOT NULL, iw_url char(127) NOT NULL, iw_local tinyint(1) NOT NULL, iw_trans tinyint(1) NOT NULL default '0', UNIQUE KEY iw_prefix (iw_prefix) ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
  
  --
• Dumping data for table wiki_interwiki --
  
  /*!40000 ALTER TABLE wiki_interwiki DISABLE KEYS */; LOCK TABLES wiki_interwiki WRITE; UNLOCK TABLES; /*!40000 ALTER TABLE wiki_interwiki ENABLE KEYS */;

The table indeed exists, but in an empty state!
People updating will always have the table, but by default empty, not nonexistent
as the program assumes... except in the rare case one has removed it
by hand.

Yes, you don't want to trample peoples customizations, but what
happens is that people see their friends can use interwiki links, but
they can't even though they've done regular updates.
So an update is not as good as a fresh install.

Version: 1.11.x
Severity: normal
URL: http://permalink.gmane.org/gmane.org.wikimedia.mediawiki/25673