A database query error has occurred. This may indicate a bug in the software.

Backtrace:

#0 /x1/mediawiki-1.23.13/includes/db/Database.php(1123): DatabaseBase->reportQueryError()
#1 /x1/mediawiki-1.23.13/includes/db/Database.php(1590): DatabaseBase->query()
#2 /x1/mediawiki-1.23.13/includes/db/Database.php(1301): DatabaseBase->select()
#3 /x1/mediawiki-1.23.13/includes/diff/DifferenceEngine.php(1298): DatabaseBase->selectField()
#4 /x1/mediawiki-1.23.13/includes/diff/DifferenceEngine.php(239): DifferenceEngine->loadRevisionData()
#5 /x1/mediawiki-1.23.13/includes/Article.php(826): DifferenceEngine->showDiffPage()
#6 /x1/mediawiki-1.23.13/includes/Article.php(549): Article->showDiffPage()
#7 /x1/mediawiki-1.23.13/includes/actions/ViewAction.php(44): Article->view()
#8 /x1/mediawiki-1.23.13/includes/Wiki.php(487): ViewAction->show()
#9 /x1/mediawiki-1.23.13/includes/Wiki.php(285): MediaWiki->performAction()
#10 /x1/mediawiki-1.23.13/includes/Wiki.php(647): MediaWiki->performRequest()
#11 /x1/mediawiki-1.23.13/includes/Wiki.php(506): MediaWiki->main()
#12 /x1/mediawiki-1.23.13/index.php(46): MediaWiki->run()
#13 {main}