---
phase: 04-tags
plan: 01
subsystem: database
tags: [drizzle, sqlite, many-to-many, tags, junction-table]

# Dependency graph
requires:
  - phase: 01-foundation
    provides: entries and images schema, repository pattern
provides:
  - tags table with case-insensitive unique constraint
  - entry_tags junction table for many-to-many relationships
  - tagRepository with findOrCreate, getAll, getById, getByEntryId, updateEntryTags
  - lower() SQL helper function for case-insensitive queries
affects: [04-02-tag-ui, 04-03-tag-filter, future-search]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - "Case-insensitive unique index using lower() SQL helper"
    - "Junction table with composite primary key"
    - "Atomic tag replacement via delete-then-insert"

key-files:
  created: []
  modified:
    - src/lib/server/db/schema.ts
    - src/lib/server/db/repository.ts

key-decisions:
  - "Tags stored with original case but matched case-insensitively"
  - "Entry tags replaced atomically (full replace, not incremental)"
  - "Orphaned tags remain in database for autocomplete history"

patterns-established:
  - "lower() helper: Use for case-insensitive SQL comparisons"
  - "Junction table: Composite PK with cascade deletes on both FKs"

# Metrics
duration: 2min
completed: 2026-01-31
---

# Phase 4 Plan 1: Tag Schema & Repository Summary

**Tags and entry_tags tables with case-insensitive uniqueness, cascade deletes, and tagRepository with atomic entry tag updates**

## Performance

- **Duration:** 2 min
- **Started:** 2026-01-31T12:02:29Z
- **Completed:** 2026-01-31T12:04:34Z
- **Tasks:** 2
- **Files modified:** 2

## Accomplishments
- Tags table with case-insensitive unique index on name using lower() helper
- Entry_tags junction table with composite primary key and cascade deletes
- TagRepository with findOrCreate, getAll, getById, getByEntryId, updateEntryTags methods
- Database schema synced via drizzle-kit push

## Task Commits

Each task was committed atomically:

1. **Task 1: Add tags schema with case-insensitive unique index** - `7dc63e6` (feat)
2. **Task 2: Create tagRepository with tag operations** - `378d928` (feat)

## Files Created/Modified
- `src/lib/server/db/schema.ts` - Added tags table, entry_tags junction table, lower() helper, type exports
- `src/lib/server/db/repository.ts` - Added TagRepository interface and SQLiteTagRepository implementation

## Decisions Made
- Store tags with original user-provided casing but match case-insensitively
- Replace entry tags atomically: delete all existing, then insert new set
- Keep orphaned tags in database (useful for autocomplete suggestions)

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

None

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness
- Tag schema and repository ready for UI integration
- Ready for plan 04-02 (tag input UI with autocomplete)
- Ready for plan 04-03 (filter by tag)

---
*Phase: 04-tags*
*Completed: 2026-01-31*
