indrasvat Migration Guard
Read-only structural analysis. CAVEAT: Lock risk predictions require live table size, row counts, and engine metadata which this skill cannot access. Treat lock assessments as directional, not definitive.
1. Detect framework
Check project root: go.mod with goose/golang-migrate/atlas (Go), drizzle.config.* (Drizzle), alembic.ini or alembic/ (Alembic), knexfile.* (Knex), raw .sql files (generic SQL). Report detected framework. If none match, analyze as raw SQL.
2. Scope
$ARGUMENTS files, or changed migration files since last commit:
git diff --name-only HEAD | grep -iE '(migrat|schema|\.sql)'
Fallback to HEAD~1 with same filter. Read every in-scope file before analysis.
3. Analysis checklist
Lock risk:
- ALTER TABLE on large tables (ADD/DROP/RENAME COLUMN, ADD/DROP INDEX)
- ADD COLUMN with DEFAULT on existing rows (Postgres <11 rewrites table)
- CREATE INDEX without CONCURRENTLY
- Column type changes forcing table rewrite
Backward compatibility:
- NOT NULL without DEFAULT (breaks old app inserts)
- Column/table DROP without deprecation period
- Column rename (old queries break immediately)
- New constraints rejecting data the old app still writes
Rollback path:
- Down/rollback migration exists?
- Rollback is data-safe (up's DROP doesn't lose data irrecoverably)?
- Forward-only justified in a comment?
Data preservation:
- Type widening safe (INT->BIGINT); narrowing dangerous (VARCHAR(255)->VARCHAR(50))
- ENUM additions safe; removals may orphan rows
- DROP COLUMN loses data permanently -- flag unless prior migration copies it
4. Output
Print summary table first:
| Check | Status | Detail |
|------------------------|--------|-------------------------------------------|
| Lock risk | WARN | ADD INDEX without CONCURRENTLY on "orders" |
| Backward compatibility | PASS | |
| Rollback path | FAIL | No down migration found |
| Data preservation | PASS | |
For each WARN/FAIL, print a recommendation below the table: the risk and a concrete remediation.
5. Idempotency
Read-only. No files created or modified. Safe to re-run.
$ARGUMENTS