Reporting here as there is no possibility of reporting version 9.4 bugs in the Bug Reporting system (?!?!? - Even if you want to decline to fix them, surely leaving them unreported hinders knowledge among users, and may suppress a bug which applies to v10 too?)
Summary: v18.104.22.168 went into a tight loop (not possible to login via web from user or admin side due to lack of response / blank screen) reporting an SQL Error "While executing query "DELETE FROM cms_session WHERE time" (sic)
Details: Host took down shared MySQL server due to load spike (not any of my sites), and restored immediately. Another of my sites recovered normally with just a few sever gone away messages, but one started these DELETE reports and continued (for hours) with several thousands of emails (2 to 6 per minute). Reports came from all modules as it tried to clear the cms_session file (on each web request?).
Attempts to access db via phpMyAdmin were successful if a little slow, but access to cms_session displayed a "Table 'cms_session' is marked as crashed and last (automatic?) repair failed"
Had to get the site back up asap as it - inevitably - occurred on a critical Sale day with client on-site with customers who were trying to access the website, so capturing further diagnostics was not possible.
Tried clearing cache, which seemed to have no effect, and then emptying the cms_session file, which worked.
Could/Should the error be dropped after a suitable count in order to service the web interface, or is there no way to continue with a problem in cms_session file?
Anything which can be done to prevent a possible recurrence?
Note also that the error message seems wrong with 'time' incomplete and the rest of the usual email message format apparently missing.
Any advice gratefully received.
[ Note I felt the empty command was appropriate as no users have access to site, only admins, who were not logged in, so every access was a visitor. ]