---
phase: 32-state-update-optimization
plan: 02
subsystem: state-management
tags: [redux, react, performance, selectors, memoization]

# Dependency graph
requires:
  - phase: 31-selector-optimization
    provides: Composed selectors with shallowEqual comparisons
provides:
  - Conditional dispatch with content comparison for mixer categorization
  - mixerArraysEqual helper for ID-based array comparison
  - prevCategoriesRef to track last dispatched category values
affects: [33-performance-testing, mixer-ui-components]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - "Content comparison before Redux dispatch"
    - "useRef for tracking previous dispatch values"
    - "ID-based array equality checking"

key-files:
  created: []
  modified:
    - jam-ui/src/hooks/useMixerHelper.js

key-decisions:
  - "Use ref instead of selectors to track previous values (avoids circular updates)"
  - "ID-based comparison via master.id + personal.id pairs (stable and fast)"
  - "Console logs for debugging dispatch decisions (can be commented out in production)"

patterns-established:
  - "Conditional dispatch pattern: if (!arrayEqual(prev, next)) { dispatch(); prev = next; }"
  - "Comparison by stable IDs rather than deep object comparison"
  - "Ref-based tracking for values that shouldn't trigger re-renders"

# Metrics
duration: 2min
completed: 2026-03-05
---

# Phase 32 Plan 02: Mixer Categorization Optimization Summary

**Conditional Redux dispatches eliminate redundant category updates - only dispatch when mixer IDs actually change**

## Performance

- **Duration:** 2 min
- **Started:** 2026-03-05T14:05:42Z
- **Completed:** 2026-03-05T14:07:07Z
- **Tasks:** 3
- **Files modified:** 1

## Accomplishments
- Added mixerArraysEqual helper for efficient ID-based array comparison
- Implemented prevCategoriesRef to track last dispatched category values
- Replaced unconditional dispatches with conditional checks for all 5 categories
- Prevents unnecessary re-renders when mixer objects change but categories stay the same

## Task Commits

Each task was committed atomically:

1. **Task 1: Add mixer array comparison helper** - `10a1eb657` (feat)
   - Added mixerArraysEqual function with ID-based comparison
   - Compares by master.id + personal.id pair keys

2. **Task 2: Add prevCategoriesRef to track dispatched values** - `f7f6f10d6` (feat)
   - Added useRef with category tracking object
   - Avoids circular updates by using ref instead of selectors

3. **Task 3: Add conditional dispatch to categorization** - `d53603cd0` (feat)
   - Wrapped all 5 category dispatches in mixerArraysEqual checks
   - Updates prevCategoriesRef after each dispatch
   - Added console logs for debugging

## Files Created/Modified
- `jam-ui/src/hooks/useMixerHelper.js` - Added content comparison before Redux dispatches

## Decisions Made

**1. Use ref instead of selectors for previous values**
- Selectors would cause circular updates (selector reads state that dispatch updates)
- Ref provides stable reference across renders without triggering re-renders
- Stores last dispatched values for next comparison

**2. ID-based comparison instead of deep equality**
- Mixer objects have stable `id` fields
- Deep comparison with JSON.stringify would be slow and fragile
- Only care if the set of mixers changed, not individual properties
- Master/personal pair creates unique identifier per mixer pair

**3. Console logs for debugging**
- Useful during development to verify dispatches being skipped
- Can be commented out in production
- Help confirm optimization is working as expected

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

**Pre-existing ESLint warnings**
- File has 60 pre-existing ESLint warnings (unused imports, missing dependencies)
- Not related to this change
- All formatting errors fixed with prettier
- New code follows existing patterns

## Next Phase Readiness

**Ready for performance testing (Phase 33):**
- Mixer categorization now only dispatches when content changes
- Expected reduction: 5 unnecessary dispatches per mixer update
- Can measure with Redux DevTools dispatch count before/after

**Impact on downstream components:**
- Any components subscribed to category selectors will re-render less frequently
- VU meter updates won't trigger category re-categorization dispatches
- Should reduce overall render count significantly

**Monitoring approach:**
- Console logs show when dispatches are skipped
- Redux DevTools can verify dispatch reduction
- React DevTools Profiler can measure render time improvements

---
*Phase: 32-state-update-optimization*
*Completed: 2026-03-05*
