In T309151#7955541, @Tacsipacsi wrote:

MariaDB [mediawikiwiki_p]> SELECT * FROM revision WHERE rev_id = 699461;
+--------+----------+----------------+-----------+----------------+----------------+-------------+---------+---------------+---------------------------------+
| rev_id | rev_page | rev_comment_id | rev_actor | rev_timestamp  | rev_minor_edit | rev_deleted | rev_len | rev_parent_id | rev_sha1                        |
+--------+----------+----------------+-----------+----------------+----------------+-------------+---------+---------------+---------------------------------+
| 699461 |        0 |         349590 |   1091377 | 20121012174843 |              0 |           0 |    2490 |             0 | b7rlqawc9gdaezbggvx2tt26tnsdsui |
+--------+----------+----------------+-----------+----------------+----------------+-------------+---------+---------------+---------------------------------+
1 row in set (0.002 sec)

MariaDB [mediawikiwiki_p]> SELECT COUNT(*) FROM revision WHERE rev_page = 0;
+----------+
| COUNT(*) |
+----------+
|      320 |
+----------+
1 row in set (0.003 sec)

It looks like the code doesn’t check whether the page exists, it just assumes that non-existent pages (page ID is 0) don’t have records in the database, but in fact there are hundreds of such records. While it looks like a database corruption, we can unblock the train by short-circuiting in case the page doesn’t exist:

diff --git a/src/TranslatorInterface/Aid/EditSummariesAid.php b/src/TranslatorInterface/Aid/EditSummariesAid.php
index 1050e3f6a..f8544234d 100644
--- a/src/TranslatorInterface/Aid/EditSummariesAid.php
+++ b/src/TranslatorInterface/Aid/EditSummariesAid.php
@@ -18,6 +18,9 @@ class EditSummariesAid extends TranslationAid {
 
        public function getData(): array {
                $pageTitle = $this->handle->getTitle();
+               if ( !$pageTitle->exists() ) {
+                       return [];
+               }
                $mwService = MediaWikiServices::getInstance();
                $revisionFactory = $mwService->getRevisionFactory();

Thanks for getting that data from production. I've submitted a patch to unblock the train.

None of the other translation aids have that check either but appear to be not having issues.

Not seeing any other occurrences of this issue since the patch was deployed via backports.