Feat: Replace UUID image identifiers with 8-character base62 short IDs

Short IDs become the canonical identifier in URLs (/i/:short_id), MinIO/R2 storage keys, and all API responses. Hash-based deduplication is preserved. Includes two-phase Alembic migration (003 adds nullable column, 004 enforces NOT NULL) with a backfill script to copy storage objects and populate short_id for existing images. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
2026-05-10 00:13:55 +00:00
parent 87eb2703f5
commit 61d923d5be
41 changed files with 1445 additions and 137 deletions
--- a/specs/017-short-id-migration/data-model.md
+++ b/specs/017-short-id-migration/data-model.md
@@ -0,0 +1,77 @@
+# Data Model: Short Image IDs
+
+## Changed Entity: Image
+
+### New Column
+
+| Column     | Type         | Constraints                  | Notes                                     |
+|------------|--------------|------------------------------|-------------------------------------------|
+| `short_id` | VARCHAR(8)   | UNIQUE, NOT NULL (post-migration), INDEX | Base62 alphanumeric, 8 characters |
+
+### Updated Columns (values change, types unchanged)
+
+| Column          | Old values                              | New values                        |
+|-----------------|-----------------------------------------|-----------------------------------|
+| `storage_key`   | SHA-256 hash (64 hex chars)             | short_id (8 base62 chars)         |
+| `thumbnail_key` | `{hash}-thumb` (69 chars)              | `{short_id}-thumb` (13 chars)     |
+
+### Unchanged Columns
+
+| Column     | Notes                                                                 |
+|------------|-----------------------------------------------------------------------|
+| `id`       | UUID primary key — unchanged, retained as internal identifier         |
+| `hash`     | SHA-256 content hash — unchanged, still used for deduplication        |
+| `filename` | Unchanged                                                             |
+| `mime_type`| Unchanged                                                             |
+| `size_bytes`, `width`, `height` | Unchanged                                    |
+| `created_at` | Unchanged                                                           |
+
+### Validation Rules
+
+- `short_id`: exactly 8 characters, matching `[a-zA-Z0-9]{8}` — generated on insert, never updated
+- `short_id` must be unique across all image records
+- On collision (rare), a new value is generated and retried (up to 10 attempts)
+
+---
+
+## Alembic Migrations
+
+### Migration 003 — Add `short_id` column (nullable)
+
+```
+ALTER TABLE images ADD COLUMN short_id VARCHAR(8) NULL;
+CREATE UNIQUE INDEX ix_images_short_id ON images (short_id);
+```
+
+Run immediately on deploy. Existing rows get `short_id = NULL`. New uploads will populate `short_id` on insert (application-level).
+
+### Migration Script — Backfill existing rows
+
+`api/scripts/migrate_to_short_ids.py`
+
+For each image where `short_id IS NULL`:
+1. Generate 8-char base62 short_id (retry on collision)
+2. Copy storage object: `{hash}` → `{short_id}` (S3 copy)
+3. Copy thumbnail if present: `{hash}-thumb` → `{short_id}-thumb`
+4. Verify new objects exist (S3 head_object)
+5. Update DB row: `short_id = {short_id}`, `storage_key = {short_id}`, `thumbnail_key = {short_id}-thumb` (or NULL)
+6. Delete old storage objects
+
+### Migration 004 — Add NOT NULL constraint
+
+```
+ALTER TABLE images ALTER COLUMN short_id SET NOT NULL;
+```
+
+Run only after the migration script completes successfully with zero `short_id IS NULL` rows remaining.
+
+---
+
+## Storage Object Naming Convention
+
+| Object type | Key pattern         | Example           |
+|-------------|---------------------|-------------------|
+| Original    | `{short_id}`        | `xK7mN2pQ`        |
+| Thumbnail   | `{short_id}-thumb`  | `xK7mN2pQ-thumb`  |
+
+No folder structure. Flat bucket layout (unchanged from current convention).