Two perf gaps that would have failed Cin's review:
# Gap #1: alias lookup fired unconditionally
Pre-fix in this commit, `_resolve_expected_artist_aliases` ran at
the top of every `verify_audio_file` call regardless of whether
the direct artist match would have passed. For users whose library
is mostly same-script (95% of cases), every successful verification
was paying for a wasted DB query (and possibly a wasted MB API
call for un-enriched artists).
Restructured the helper to accept a callable provider instead of a
pre-resolved list. Provider invoked LAZILY only when direct
similarity falls below `ARTIST_MATCH_THRESHOLD`. Verifier passes a
memoising thunk that resolves once across the 3 comparison sites
within one verification.
`_alias_aware_artist_sim` now accepts `aliases` as either:
- iterable of strings (used eagerly — backward compat with tests
that already know the aliases)
- callable returning the iterable (resolved on first need within
a verification)
Happy path (direct match passes): zero DB queries, zero MB calls.
Cross-script case: one resolution shared across 3 sites — same as
the prior contract.
# Gap #2: existing-MBID artists never got alias backfill
Worker's `_process_item` artist branch had an `existing_id` short-
circuit (line 296) that updated MBID status but skipped alias
fetch. Result: every user with an already-enriched library had
MBIDs but NULL aliases on day-one of this PR. Live MB lookup at
verify-time covered them, but at the cost of N live calls for N
artists across the library.
Added one-time backfill: when existing-MBID is found AND
`artists.aliases` for that row is empty, fetch + persist aliases.
Subsequent re-scan cycles short-circuit on the populated column —
no repeated MB calls.
New helper `_artist_aliases_empty(artist_id)` does the cheap NULL
check via direct SQL. Best-effort: defensively returns True on
errors so backfill happens (a redundant MB call is cheaper than
missing the backfill entirely).
# Tests added (9)
`test_acoustid_verification_aliases.py` (+6):
- `TestLazyAliasResolution` (3): no lookup when direct match passes,
lookup fires only when direct fails, lookup memoised across the
3 sites within one verification.
- `TestAliasProviderCallable` (3): iterable passed directly,
callable resolves lazily, callable returning empty falls back to
direct sim.
`test_artist_alias_service.py` (+3):
- `test_existing_mbid_path_backfills_aliases_when_column_empty`
- `test_existing_mbid_path_skips_backfill_when_aliases_already_set`
- `test_existing_mbid_backfill_failure_does_not_break_match`
# Verification
- 79/79 matching tests pass (+9 from prior commit)
- 2537 full suite passes (+9, +79 PR-total)
- Ruff clean
- Backward compat: every prior-commit test still passes (the
iterable-shape API still works alongside the new callable shape)
11397307b2