Review of 491f5099 found the fix inert in the only process that runs it, plus
a MySQL collation defect in the lookup.
B1 — TvContext.IsUniqueConstraintViolation was assigned only in ErsatzTV/
Startup.cs, but ErsatzTV.Scanner is a separate executable and every production
caller of GetOrAddFolder/SetEtag lives there. The classifier kept its '_ =>
false' default, so the catch never ran and the DbUpdateException failed the
whole scan - worse than the duplicate row it replaced. Wire both provider
branches in ErsatzTV.Scanner/Program.cs, and add ProviderStaticsWiringTests
(architecture) asserting the scanner assigns every TvContext static the host
assigns, with IsSqlite documented as the one exemption.
H1 — GetFolder's 'Path == folder' is case-insensitive on MySQL while PathHash
is case-sensitive, and FirstOrDefault was unordered: a scan of '/x/foo' could
resolve the '/x/Foo' row and stamp the wrong hash onto it (verified on MySQL
8.4: the WHERE matches both, LIMIT 1 returns the wrong one). Treat the SQL
equality as a narrowing filter, order by Id, and settle identity ordinally.
Route the heal through EF and drop a classified violation, so an opportunistic
maintenance write can never abort a scan.
Also: run the dedupe migration test with foreign keys ON (matching prod), clear
the keeper's etag, null out a self-parent, and document the cleanup's limits
(NULL paths excluded, Down does not restore deleted rows, CI's fresh-DB apply
covers none of the data mutation).
Refs #488#308fix#491
timothy
14e9b03433