After installing the CheckUser extension on MediaWiki 1.33.1 and a PostgreSQL database, it is not possible to create a new user due to the following error. Obviously, there can't be a page with page_id = 0, so why is cuc_page_id being set to 0? It should be NULL if it is unknown/non-existent...
This is a very similar or even the same case as T149973.
[a14de166292ecc11ddb7703a] /index.php/Special:CreateAccount Wikimedia\Rdbms\DBQueryError from line 1587 of /srv/http/LocalArchWiki/includes/libs/rdbms/database/Database.php: A database query error has occurred. Did you forget to run your application's database schema updater after upgrading? Query: INSERT INTO "cu_changes" (cuc_page_id,cuc_namespace,cuc_title,cuc_minor,cuc_user,cuc_user_text,cuc_actiontext,cuc_comment,cuc_this_oldid,cuc_last_oldid,cuc_type,cuc_timestamp,cuc_ip,cuc_ip_hex,cuc_xff,cuc_xff_hex,cuc_agent) VALUES ('0','2','','0','7','Test','was created','','0','0','3','2020-01-03 10:42:48+00','127.0.0.1','7F000001',0,NULL,'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) QtWebEngine/5.14.0 Chrome/77.0.3865.129 Safari/537.36') Function: CheckUserHooks::logUserAccountCreation Error: 23503 ERROR: insert or update on table "cu_changes" violates foreign key constraint "cu_changes_cuc_page_id_fkey" DETAIL: Key (cuc_page_id)=(0) is not present in table "page". Backtrace: #0 /srv/http/LocalArchWiki/includes/libs/rdbms/database/Database.php(1556): Wikimedia\Rdbms\Database->getQueryExceptionAndLog() #1 /srv/http/LocalArchWiki/includes/libs/rdbms/database/Database.php(1274): Wikimedia\Rdbms\Database->reportQueryError() #2 /srv/http/LocalArchWiki/includes/libs/rdbms/database/DatabasePostgres.php(621): Wikimedia\Rdbms\Database->query() #3 /srv/http/LocalArchWiki/extensions/CheckUser/includes/CheckUserHooks.php(248): Wikimedia\Rdbms\DatabasePostgres->insert() #4 /srv/http/LocalArchWiki/extensions/CheckUser/includes/CheckUserHooks.php(209): CheckUserHooks::logUserAccountCreation() #5 /srv/http/LocalArchWiki/includes/Hooks.php(174): CheckUserHooks::onLocalUserCreated() #6 /srv/http/LocalArchWiki/includes/Hooks.php(234): Hooks::callHook() #7 /srv/http/LocalArchWiki/includes/auth/AuthManager.php(1426): Hooks::runWithoutAbort() #8 /srv/http/LocalArchWiki/includes/auth/AuthManager.php(1143): MediaWiki\Auth\AuthManager->continueAccountCreation() #9 /srv/http/LocalArchWiki/includes/specialpage/AuthManagerSpecialPage.php(357): MediaWiki\Auth\AuthManager->beginAccountCreation() #10 /srv/http/LocalArchWiki/includes/specialpage/AuthManagerSpecialPage.php(482): AuthManagerSpecialPage->performAuthenticationStep() #11 /srv/http/LocalArchWiki/includes/htmlform/HTMLForm.php(660): AuthManagerSpecialPage->handleFormSubmit() #12 /srv/http/LocalArchWiki/includes/specialpage/AuthManagerSpecialPage.php(416): HTMLForm->trySubmit() #13 /srv/http/LocalArchWiki/includes/specialpage/LoginSignupSpecialPage.php(313): AuthManagerSpecialPage->trySubmit() #14 /srv/http/LocalArchWiki/includes/specialpage/SpecialPage.php(569): LoginSignupSpecialPage->execute() #15 /srv/http/LocalArchWiki/includes/specialpage/SpecialPageFactory.php(558): SpecialPage->run() #16 /srv/http/LocalArchWiki/includes/MediaWiki.php(288): MediaWiki\Special\SpecialPageFactory->executePath() #17 /srv/http/LocalArchWiki/includes/MediaWiki.php(865): MediaWiki->performRequest() #18 /srv/http/LocalArchWiki/includes/MediaWiki.php(515): MediaWiki->main() #19 /srv/http/LocalArchWiki/index.php(42): MediaWiki->run() #20 {main}