plans: §4 sub-PR 2.2 spike memo (discogs-cache match score shape)#794
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plans: §4 sub-PR 2.2 spike memo (discogs-cache match score shape)#794jakebromberg wants to merge 1 commit into
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Audits the two questions §4 sub-PR 2.2 spelled out as preconditions for
implementation. Both findings invalidate the plan's central assumption:
1. Neither flowsheet_match nor fuzzy_resolved has a trgm_score column.
- flowsheet_match is an exact equi-join on normalized strings; no fuzzy
score because no fuzzy match. The plan's `0.7 + 0.3 * trgm_score`
trigram fallback is dead code; alias_match 0.75 is the only viable
mapping for distinct_entities > 1.
- fuzzy_resolved discards the trigram score during its resolve step;
the score lives only on the un-persisted `fuzzy_full` staging table
as `combined = similarity(artist) + similarity(album) ∈ [1.55, 2.0]`.
2. fuzzy_resolved carries no Discogs ID at all — only resolved_library_id.
The master-vs-release decision applies only to flowsheet_match (S3),
where the upstream prefers master and falls back to release; recommended
mapping is option (c): write whichever the source row pins, never both.
Recommendation: split sub-PR 2.2 into 2.2a (flowsheet_match) + 2.2b
(fuzzy_resolved). The two mapping logics diverge enough — confidence
formula, Discogs ID handling, writer contract — that bisecting cleanly
warrants the second PR.
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This was referenced May 10, 2026
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Summary
Spike memo at
plans/library-hook-canonicalization/audits/discogs-cache-match-score-shape.mdauditing the two questions §4 sub-PR 2.2 spelled out as preconditions for implementation.The original second commit on this branch (a plan amendment splitting §4 sub-PR 2.2 into 2.2a + 2.2b) has been dropped because the architecture pivot in #800 supersedes it — Backend will no longer implement source-leg backfills directly. LML owns identity resolution end-to-end; Backend caches the verdict via a single bulk-resolve endpoint.
The spike findings stand on their own as reference for LML's own resolution logic, so this PR is narrowed to the memo only.
Spike findings (still valid as reference)
flowsheet_matchnorfuzzy_resolvedhas atrgm_scorecolumn. The original plan's0.7 + 0.3 * trgm_scoretrigram fallback was dead code.flowsheet_matchis an exact equi-join (no fuzzy score by construction);fuzzy_resolveddiscards the score during its resolve step (onlyarray_agg(library_id ORDER BY combined DESC)survives).fuzzy_resolvedcarries no Discogs ID — onlyresolved_library_id. The master-vs-release decision applies only toflowsheet_match, where the upstream pins one or the other.These observations belong to LML's resolution domain post-pivot but are documented here so the reasoning isn't lost.
Test plan
npm run format:check— clean.Backend-Service/scripts/discogs-bridge-flowsheet.sqlandfuzzy-trigram-flowsheet.sql.Refs #663, #800.