Claudio Ortolina
80 lines
3.9 KiB
Markdown
80 lines
3.9 KiB
Markdown
---
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id: ML-169.2
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title: "Phase 4: Performance low-hanging fruit audit"
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status: Done
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assignee: []
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created_date: "2026-05-08 08:59"
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updated_date: "2026-05-19 08:50"
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labels:
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- audit
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- ready
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dependencies: []
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references:
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- lib/music_library_web/live/stats_live/index.ex
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- lib/music_library_web/live_helpers/index_actions.ex
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- lib/music_library_web/live_helpers/record_actions.ex
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- .agents/skills/query-reporter/SKILL.md
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- /tmp/queries-ml-audit.sql
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- >-
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backlog/documents/doc-27 -
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Phase-4-Performance-Audit-Low-Hanging-Fruit-Findings.md
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parent_task_id: ML-169
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priority: medium
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ordinal: 2000
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---
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## Description
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<!-- SECTION:DESCRIPTION:BEGIN -->
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Identify unnecessary DB queries, redundant full-stream reloads, server round trips that could be client-side, missing optimistic UI opportunities, and blocking mount work that could be deferred.
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Use QueryReporter skill to capture SQL traces for key page loads as evidence.
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Key pre-flagged areas:
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- StatsLive.Index: 5 synchronous queries in mount (TTFB impact)
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- Display toggle (grid/list): full FTS query when CSS-only suffices
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- ScrobbleRulesLive + OnlineStoreTemplateLive: redundant stream_insert + immediate full reload
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- ScrobbledTracksLive + StatsLive: full stream reset on every scrobble batch instead of incremental insert
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- Search inputs: verify phx-debounce is set
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<!-- SECTION:DESCRIPTION:END -->
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## Acceptance Criteria
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<!-- AC:BEGIN -->
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- [x] #1 SQL traces captured via QueryReporter for /collection, /collection/:id, /stats, /artists/:id
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- [x] #2 Stream reset audit complete: every stream(:name, data, reset: true) call site evaluated for incremental-update alternatives
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- [x] #3 Display toggle (grid/list) evaluated: confirmed whether CSS-only toggle can replace full DB reload
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- [x] #4 StatsLive.Index mount blocking work quantified: 5 queries identified, assign_async feasibility assessed
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- [x] #5 Search input debounce verified: phx-debounce attribute presence checked on all search forms
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- [x] #6 Optimistic UI opportunities identified for delete, form save, toggle operations
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- [x] #7 N+1 audit complete: handle_params, stream rendering, and LiveComponent Repo calls checked
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- [x] #8 Findings report written as a Backlog.md document with file:line references, severity ratings, and fix recommendations
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<!-- AC:END -->
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## Final Summary
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<!-- SECTION:FINAL_SUMMARY:BEGIN -->
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## Audit Complete: 9 findings across 4 severity levels
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**SQL traces captured** via QueryReporter at `/tmp/queries-ml-audit.sql` for all 4 key pages (StatsLive, CollectionLive.Index, CollectionLive.Show, ArtistLive.Show).
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### Key findings:
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**HIGH severity (3)**:
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1. **Display toggle triggers full DB reload** — grid/list toggle in `handle_set_display` re-executes FTS search when CSS-only toggle suffices. Fix: remove `load_and_assign_records` call.
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2. **StatsLive.Index mount: 10 sync queries** — home page TTFB blocked by 10 sequential queries. `assign_async` already used elsewhere on the same page — extend it to cover heavy queries.
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3. **Scrobble updates trigger full stream reset** — every 5-minute cron batch causes `reset: true` on all connected clients for both StatsLive and ScrobbledTracksLive.
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**MEDIUM severity (4)**: 4. **Redundant stream_insert + immediate full reload** in ScrobbleRulesLive and OnlineStoreTemplateLive — `stream_insert` is immediately nullified by `load_and_assign_*`. 5. **Full resets on pagination** — `reset: true` on page changes when append could suffice. 6. **Missing optimistic UI** for delete operations — DB waits block UI. 7. **Correlated subqueries** in `ListeningStats.tracks_with_record_info_query` — 3 subqueries per row × 100 tracks.
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**PASS (2)**: 8. All search inputs have `phx-debounce` set. 9. No direct N+1 issues found in LiveView/LiveComponent layer (no direct Repo calls).
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Full report: `docs/backlog/documents/doc-27` — includes file:line references, SQL traces, and fix recommendations for each finding.
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<!-- SECTION:FINAL_SUMMARY:END -->
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