convex/songProgress.ts (2)

233-244: ⚠️ Potential issue | 🟠 Major

Add composite index on (userId, songId) to lineProgress table to avoid full per-user scans.

The current query uses withIndex("by_user") which fetches all of a user's lineProgress rows regardless of song, then filters songId and lineNumber in memory. As a user learns more lines across more songs, this scan grows unboundedly. The schema has composite indexes for visitorId combinations but not for userId. Adding an index on (userId, songId) — or (userId, songId, lineNumber) for a point-lookup — would reduce this to O(lines in song) or O(1).

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@convex/songProgress.ts` around lines 233 - 244, The query on lineProgress
using withIndex("by_user") performs a full per-user scan and then filters songId
and lineNumber in memory; add a composite index on (userId, songId) or (userId,
songId, lineNumber) to the lineProgress table schema so the query becomes
index-backed (update the schema/index definitions for lineProgress to include an
index keyed by userId+songId or userId+songId+lineNumber) and then switch the
query to use that index (replace withIndex("by_user") with the new index name)
so lookups by userId/songId/(lineNumber) are efficient.

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225-303: ⚠️ Potential issue | 🟡 Minor

Add a regression test for the toggleLineLearned mutation to verify multi-song lineNumber collision is prevented.

The mutation's fix correctly filters by both songId and lineNumber combined, but this critical logic lacks test coverage. Without a targeted test, the bug—where toggling a line in one song could affect another song with the same line number—could silently regress. Add a Convex integration test that verifies toggling line N in song A does not affect song B's line N.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@convex/songProgress.ts` around lines 225 - 303, Add a Convex integration
regression test for the toggleLineLearned mutation that ensures toggling a line
for one song does not affect another song with the same lineNumber: set up two
distinct songs (songA, songB), call toggleLineLearned with songA and lineNumber
N, then query the lineProgress and userSongProgress collections to assert a
lineProgress/userSongProgress was created/updated for songA but no lineProgress
or song progress exists or was modified for songB; reference the mutation name
toggleLineLearned and the collections/records "lineProgress" and
"userSongProgress" when locating where to add the assertions.