The SqlServer purge read every TagId and issued at least one DELETE TOP per
table per tag on every pass, even when nothing was eligible: 50000 tags made
100000 statements per hourly purge, serialised on one connection under the
applock.
One pre-filter query per table (EXISTS seek on the clustered key) now picks
the tags holding a row older than the cutoff; only those get deletes. A pass
with nothing eligible sends just the Event delete. The mid-command
cancellation test now accepts the pre-filter SELECT as the blocked command,
since it is the first statement to touch Sample.
Rebased from the unpushed remed/lane-H2 branch (originally authored 2026-10-22
in session_01Ub9hGmYLQvn9XETzw7CMsT) onto current master.
Claude-Session: https://claude.ai/code/session_01GT67AEHd2Acv1YPwGfXEoV
Joseph Doherty
d44e58dcd6