Errors seen in logstash:
Bad value for parameter $dbkey: invalid DB key 'The_Gospel_of_Jesus_Christ_Attributed_to_John_the_' #0 /srv/mediawiki/php-1.29.0-wmf.16/includes/title/TitleValue.php(82): Wikimedia\Assert\Assert::parameter(boolean, string, string) #1 /srv/mediawiki/php-1.29.0-wmf.16/includes/cache/LinkBatch.php(176): TitleValue->__construct(integer, string) #2 /srv/mediawiki/php-1.29.0-wmf.16/includes/cache/LinkBatch.php(140): LinkBatch->addResultToCache(LinkCache, Wikimedia\Rdbms\ResultWrapper) #3 /srv/mediawiki/php-1.29.0-wmf.16/includes/cache/LinkBatch.php(127): LinkBatch->executeInto(LinkCache) #4 /srv/mediawiki/php-1.29.0-wmf.16/includes/search/SearchEngine.php(557): LinkBatch->execute() #5 /srv/mediawiki/php-1.29.0-wmf.16/includes/search/SearchEngine.php(497): SearchEngine->processCompletionResults(string, SearchSuggestionSet) #6 /srv/mediawiki/php-1.29.0-wmf.16/extensions/CirrusSearch/includes/CirrusSearch.php(639): SearchEngine->completionSearch(string) #7 /srv/mediawiki/php-1.29.0-wmf.16/includes/api/ApiQueryPrefixSearch.php(54): CirrusSearch->completionSearchWithVariants(string) #8 /srv/mediawiki/php-1.29.0-wmf.16/includes/api/ApiQueryPrefixSearch.php(41): ApiQueryPrefixSearch->run(ApiPageSet) #9 /srv/mediawiki/php-1.29.0-wmf.16/includes/api/ApiPageSet.php(178): ApiQueryPrefixSearch->executeGenerator(ApiPageSet) #10 /srv/mediawiki/php-1.29.0-wmf.16/includes/api/ApiPageSet.php(142): ApiPageSet->executeInternal(boolean) #11 /srv/mediawiki/php-1.29.0-wmf.16/includes/api/ApiQuery.php(236): ApiPageSet->execute() #12 /srv/mediawiki/php-1.29.0-wmf.16/includes/api/ApiMain.php(1543): ApiQuery->execute() #13 /srv/mediawiki/php-1.29.0-wmf.16/includes/api/ApiMain.php(544): ApiMain->executeAction() #14 /srv/mediawiki/php-1.29.0-wmf.16/includes/api/ApiMain.php(515): ApiMain->executeActionWithErrorHandling() #15 /srv/mediawiki/php-1.29.0-wmf.16/api.php(83): ApiMain->execute() #16 /srv/mediawiki/w/api.php(3): include(string) #17 {main}
Seems to affect around 100 queries per minute.