Migration Impact Analyzer

The Migration Impact Analyzer scans your codebase before running migrations to detect breaking changes that could cause runtime errors.

Why Use It?

Dropping a table or column is easy—but if your code still references it, you’ll get runtime errors. The analyzer:

Scans your codebase for QAIL and raw SQL queries
Detects breaking changes like dropped tables/columns
Shows exact file locations where code needs updating
Prevents downtime by catching issues before they hit production

Usage

qail migrate analyze old.qail:new.qail --codebase ./src

Example Output

🔍 Migration Impact Analyzer

  Schema: old.qail → new.qail
  Codebase: ./src

Scanning codebase...
  Found 395 query references

⚠️  BREAKING CHANGES DETECTED

Affected files: 1

┌─ DROP TABLE promotions (6 references) ─────────────────────────┐
│ ❌ src/repository/promotion.rs:89 → INSERT INTO promotions (
│ ❌ src/repository/promotion.rs:264 → SELECT COUNT(*) FROM promotions
│ ❌ src/repository/promotion.rs:288 → UPDATE promotions SET
│ ❌ src/repository/promotion.rs:345 → DELETE FROM promotions WHERE
└────────────────────────────────────────────────────────────────┘

What would you like to do?
  1. Run anyway (DANGEROUS - will cause 1 runtime errors)
  2. Dry-run first (show SQL, don't execute)
  3. Let me fix the code first (exit)

Supported Query Patterns

The analyzer detects:

QAIL Queries

get::users → SELECT from users
set::users → UPDATE users
add::users → INSERT INTO users
del::users → DELETE FROM users

Raw SQL

SELECT ... FROM table
INSERT INTO table
UPDATE table SET
DELETE FROM table

Supported File Types

.rs (Rust)
.ts (TypeScript)
.js (JavaScript)
.py (Python)

Breaking Change Types

Change Type	Severity	Description
`DROP TABLE`	🔴 Critical	Table referenced in code will cause runtime errors
`DROP COLUMN`	🔴 Critical	Column queries will fail
`RENAME`	🟡 Warning	Code needs updating to use new name
`TYPE CHANGE`	🟡 Warning	May cause type mismatch errors

Best Practices

Always run before migrate up

qail migrate analyze old.qail:new.qail --codebase ./src
qail migrate up old.qail:new.qail $DATABASE_URL

Add to CI/CD pipeline

- name: Check migration safety
  run: qail migrate analyze $OLD:$NEW --codebase ./src

Use with migrate plan for full preview

qail migrate plan old.qail:new.qail     # See SQL
qail migrate analyze old.qail:new.qail  # Check codebase
qail migrate up old.qail:new.qail $URL  # Apply

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