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
GetOrAddFolder was a check-then-insert with no unique constraint behind it,
so two callers racing the same folder could both miss the lookup and both
insert. Enforce identity in the schema and make the loser adopt the winner.
- LibraryFolder gains a SHA-256 PathHash (the MediaFile.Path/PathHash
precedent): Path is MySQL longtext, which cannot be indexed without a
prefix length and collates case-insensitively, so the unique index is on
(LibraryPathId, PathHash) instead.
- GetOrAddFolder and SetEtag catch a classified unique violation via the
existing TvContext.IsUniqueConstraintViolation seam (#308) and re-read.
- Dual-provider migration audits and collapses pre-existing duplicates
(repointing MediaFile, ParentId and ImageFolderDuration) before creating
the index; legacy rows keep a null hash and heal on the next scan.
- Tests: deterministic cross-connection race, 8x10 barrier stress with an
insert-attempt vacuity guard, classifier-inversion negative control, and
a real-migration dedupe test.
Refs #488#308fix#491
timothy