clicking Download Discography → Add all to wishlist added ~1 track every 15-30s. trace: the
endpoint's per-track library-ownership check (track_already_owned → check_track_exists) ran the
LEGACY path — firing search_tracks for every title-variation × artist-variation, per track. on
a large library and an artist you own NOTHING of, STRATEGY-1 (indexed LIKE) always missed and
fell through to the fuzzy fallback (full-table scan), ~10-15 scans/track = the 15-30s. metadata
fetch was never the bottleneck (deezer returns each album in ~1s).
fix: pre-fetch the artist's owned tracks ONCE (get_candidate_albums_for_artist →
get_candidate_tracks_for_albums) and pass candidate_tracks to check_track_exists's batched
in-memory path — the same path the discography backfill job + completion-stream already use.
pass an EMPTY list (not None) when nothing is owned so the owns-nothing case still takes the
fast path → instant. per-track cost drops from ~20s to ~1ms.
safe: track_already_owned's only real caller is this endpoint; the new param is optional
(None = unchanged legacy behaviour for any other caller). normal ownership still detected (same
artist-variation breadth); the one divergence is a track owned ONLY via a compilation → a
harmless redundant wishlist add, which is the endpoint's explicitly-accepted failure mode and
already how the backfill job behaves. 4 new tests; 1134 discog/metadata/wishlist tests green.
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