migrationpilot

MigrationPilot

Block unsafe Postgres migrations before merge.

Local, deterministic analysis for PostgreSQL migrations. Uses PostgreSQL's parser, checks 112 rules, and exits non-zero in CI. No account required. MIT.

npx migrationpilot analyze migration.sql

Try it in your browser · GitHub Action · Documentation

Benchmark

Tool	Strict detection	False positives
MigrationPilot	30/33 (90.9%)	1/17 (5.9%)
Squawk	20/33 (60.6%)	1/17 (5.9%)
pgfence	25/33 (75.8%)	3/17 (17.6%)

56 labelled files. Author-built corpus. Tools pinned.

Methodology · Corpus · What MigrationPilot missed · Reproduce: pnpm build && node bench/run.mjs

A finding

-- migration.sql
ALTER TABLE users ADD CONSTRAINT users_email_unique UNIQUE (email);

$ migrationpilot analyze migration.sql

  ✗ MigrationPilot —  RED  Score: 80/100
  migration.sql
  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─  ─
  1 statement · 2 critical · rollback GREEN

┌─────┬──────────────────────────────────────────────────┬─────────────────────────┬────────┬───────┐
│ #   │ Statement                                        │ Lock Type               │ Risk   │ Long? │
├─────┼──────────────────────────────────────────────────┼─────────────────────────┼────────┼───────┤
│ 1   │ ALTER TABLE users ADD CONSTRAINT users_ema...    │ ACCESS EXCLUSIVE        │  YELL… │ YES   │
└─────┴──────────────────────────────────────────────────┴─────────────────────────┴────────┴───────┘

  Violations:

  ✗ [MP004] CRITICAL (line 1)
    DDL statement acquires ACCESS EXCLUSIVE lock without a preceding SET lock_timeout. Without a timeout, this statement could block the lock queue indefinitely if it can't acquire the lock, causing cascading query failures.

    Safe alternative:
    -- Set a timeout so DDL fails fast instead of blocking the queue
    SET lock_timeout = '5s';
    ALTER TABLE users ADD CONSTRAINT users_email_unique UNIQUE (email)
    RESET lock_timeout;

    Why: Without lock_timeout, if the table is locked by another query, your DDL waits indefinitely. All subsequent queries pile up behind it in the lock queue, causing cascading timeouts across your application. GoCardless enforces a 750ms lock_timeout for this reason.
    Docs: https://migrationpilot.dev/rules/mp004

  ✗ [MP027] CRITICAL (line 1)
    Adding UNIQUE constraint "users_email_unique" on "users" scans the entire table under ACCESS EXCLUSIVE lock. Create the index concurrently first, then use USING INDEX.

    Safe alternative:
    -- Step 1: Create the unique index concurrently (non-blocking)
    CREATE UNIQUE INDEX CONCURRENTLY users_email_unique_idx ON users (...);

    -- Step 2: Add the constraint using the pre-built index (instant)
    ALTER TABLE users ADD CONSTRAINT users_email_unique UNIQUE USING INDEX users_email_unique_idx;

    Why: ALTER TABLE ADD CONSTRAINT UNIQUE builds a unique index while holding ACCESS EXCLUSIVE lock, blocking all reads and writes for the entire scan. Instead, create the unique index concurrently (non-blocking), then attach it as a constraint with USING INDEX.
    Docs: https://migrationpilot.dev/rules/mp027

  Risk Factors:
    Lock Severity        ██████████ 40/40 — ACCESS EXCLUSIVE (long-held)
    Rule Violations      ████████░░ 80/100 — 2 critical

  112 rules checked in 11ms

Exit code is 2. The headline is RED because critical violations fired; the per-statement Risk column stays YELLOW because table size and query frequency are unknown without a database connection. See Production context.

Contents

Install · AI coding agents · CI · What it checks · Beyond one file · Configuration · Output · Production context · Comparison · Pricing · Architecture · API

Install

npx migrationpilot analyze migration.sql   # no install
npm install -g migrationpilot              # global

Node 22 or newer. The PostgreSQL parser ships compiled in, so there is nothing else to set up. Exit codes are the same everywhere: 0 clean, 1 warnings under --fail-on warning, 2 critical.

Packaged builds land with v1.6.0, including single-file executables for Linux, macOS and Windows on the release page for machines without Node:

brew install mickelsamuel/migrationpilot/migrationpilot
docker run --rm -v "$PWD:/work" ghcr.io/mickelsamuel/migrationpilot:v1 analyze /work/migration.sql

AI coding agents

Agents write migrations now. They are good at SQL and bad at knowing which statement takes an ACCESS EXCLUSIVE lock on a table with 40 million rows, and by then the outage has already happened.

MCP server. Seven tools, the important one being check_before_apply: a pass/fail gate the agent calls before it writes or runs DDL. It resolves your .migrationpilotrc.yml exactly like the CLI does, so its verdict is the verdict CI will give.

{
  "mcpServers": {
    "migrationpilot": { "command": "npx", "args": ["migrationpilot-mcp"] }
  }
}

Tool	Purpose
check_before_apply	{sql, pgVersion?, configPath?} returns {verdict: pass|fail, failOn, violations[], summary}
analyze_migration	Violations, risk score and lock analysis for one migration
analyze_migration_dir	Per-file results plus an aggregate for a whole folder
get_rule	What a rule reports, why it matters, whether it auto-fixes
suggest_fix	Auto-fixed SQL plus the violations that need a human
explain_lock	The lock one DDL statement takes and what it blocks
list_rules	The full catalogue

Claude Code plugin. integrations/claude-code/ pairs a skill that tells Claude to check migrations with a PreToolUse hook that blocks the tool call when it doesn't. It fails open on purpose: a missing install, unparseable SQL, or a timeout lets the call through with a note on stderr, because a guardrail that breaks your workflow when it can't run gets uninstalled.

claude plugin install ./integrations/claude-code

Cursor and Copilot. Copy integrations/cursor/migrationpilot.mdc into .cursor/rules/, or paste integrations/copilot/copilot-instructions-snippet.md into .github/copilot-instructions.md. Both tell the agent when to run MigrationPilot and that suppressing a rule to get past a violation is the user's call, not the agent's.

CI

GitHub Action

# .github/workflows/migration-check.yml
name: Migration Safety Check
on: [pull_request]

jobs:
  check:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: mickelsamuel/migrationpilot@v1
        with:
          migration-path: "migrations/*.sql"
          fail-on: critical

Posts a report as a PR comment, fails the check on critical violations, and writes SARIF for Code Scanning.

Input	Description	Default
migration-path	Glob for SQL files (required)
github-token	Token for PR comments	${{ github.token }}
pg-version	Target PostgreSQL version	17
fail-on	critical, warning, irreversible, never	critical
exclude	Comma-separated rule IDs to skip
config-file	Path to .migrationpilotrc.yml	auto-detected
database-url	Connection for production context
license-key	Org plan license key

Outputs: risk-level, violations, sarif-file.

Pre-commit

migrationpilot hook install writes a plain git hook and is Husky-aware. With the pre-commit framework instead:

repos:
  - repo: https://github.com/mickelsamuel/migrationpilot
    rev: v1.6.0
    hooks:
      - id: migrationpilot
        args: [--fail-on, warning]

Clean files print nothing. Only migrations with violations are reported.

GitLab CI

include:
  - remote: 'https://raw.githubusercontent.com/mickelsamuel/migrationpilot/v1.6.0/integrations/gitlab/.gitlab-ci-migrationpilot.yml'

migrationpilot:
  variables:
    MIGRATIONPILOT_PATH: db/migrate

Runs on merge requests that touch migrations, keeps the JSON report as an artifact, and annotates the MR diff through GitLab Code Quality.

What it checks

112 rules: 34 critical, 78 warning, 20 auto-fixable with --fix. Ten that matter most:

Rule	Fix	What it catches
MP001	Yes	CREATE INDEX without CONCURRENTLY blocks writes for the whole build
MP002		SET NOT NULL scans the full table. Use the validated CHECK pattern
MP003		ADD COLUMN with a volatile DEFAULT rewrites the table and its indexes
MP007		ALTER COLUMN TYPE rewrites the table under ACCESS EXCLUSIVE
MP008		Several DDL statements in one transaction compound the lock duration
MP025	Yes	CONCURRENTLY inside a transaction is a runtime ERROR, not a warning
MP027		UNIQUE constraint without USING INDEX scans the table under an exclusive lock
MP055		Dropping a primary key breaks logical replication
MP070		A failed concurrent build leaves an invalid index the retry silently inherits
MP097		Dropping the index behind a constraint is rejected and aborts the migration

Browse all 112 rules, or run migrationpilot explain MP027 for one. The handbook is 20 chapters on why each hazard bites and what to do instead.

Rules adapt to --pg-version (9 through 20): REINDEX CONCURRENTLY from 12, DETACH PARTITION CONCURRENTLY from 14, the native NOT NULL ... NOT VALID path from 18.

Beyond one file

analyze --fix rewrites the 20 fixable violations in place. The rest of the surface:

Command	What it does
check <dir>	Whole directory, plus cross-file sequence analysis
simulate	Runs the migration against an ephemeral in-process PostgreSQL 18 (PGlite) and reports what actually happened
plan-fix	Step-by-step expand-contract plan for violations with no one-line fix, with deploy boundaries
mutation-test	Mutates passing migrations into dangerous near-neighbours to find holes in your config
predict	Duration estimate for an operation, calibrated by --row-count and --size
template	Generates expand-contract SQL for renames, type changes, NOT NULL, and more
plan	Visual execution timeline: lock, duration, blocking impact, transaction boundaries
rollback	Reverse DDL, graded by how recoverable it is
drift	Diffs two live schemas
precommit	Multi-file entry point the pre-commit framework calls

Twenty-four commands in total. migrationpilot --help lists them.

Sequence analysis is what a per-file linter cannot see. Three migrations that each look fine can still take one table down together:

$ migrationpilot check migrations/

  ⚠ [SQ001] WARNING cumulative-lock-budget
    "orders" is locked for an estimated 2m across 2 statements in 2 files — over the 1m budget for one deploy.
  ⚠ [SQ002] WARNING hot-table-multi-touch
    "orders" is locked by 3 files in this sequence. Each one queues behind live traffic on its own — fold them into one migration so the table takes the hit once.

Tune it with --lock-budget <seconds> and --hot-table-threshold <files>, turn it off with --no-sequence, and make it blocking with --fail-on-sequence.

--fail-on irreversible is stricter than critical: it also blocks migrations that destroy data with no down file.

Configuration

Zero-config is the default. check with no directory detects your framework, finds its migrations, and analyzes them in apply order. Fourteen are supported: Flyway, Liquibase, Alembic, Django, Knex, Prisma, TypeORM, Drizzle, Sequelize, goose, dbmate, Sqitch, Rails, Ecto. Force one with --framework prisma, or pipe any generator through --from-command:

migrationpilot check --from-command "python manage.py sqlmigrate myapp 0042"

# .migrationpilotrc.yml
extends: "migrationpilot:strict"
pgVersion: 16
failOn: warning
rules:
  MP037: false                 # off
  MP004: { severity: warning } # downgrade
  MP013: { threshold: 5000 }   # retune
ignore:
  - "migrations/seed_*.sql"

Five presets: recommended (default), strict, ci, startup, enterprise. Inline, -- migrationpilot-disable MP001 suppresses a rule for the next statement and -- migrationpilot-disable-file MP001 does it for the whole file. Name no rule and it suppresses all of them.

Ed25519 license keys validate client-side. --offline skips update checks and every other network call. There is no telemetry.

Output

--format text (default), json, sarif, or markdown, plus --quiet for one gcc-style line per violation and --verbose for per-statement pass/fail.

{
  "$schema": "https://migrationpilot.dev/schemas/report-v1.json",
  "version": "1.6.0",
  "file": "migrations/001.sql",
  "riskLevel": "RED",
  "riskScore": 80,
  "violations": []
}

SARIF feeds GitHub Code Scanning, VS Code and IntelliJ: migrationpilot analyze migration.sql --format sarif --output results.sarif.

Production context

Pass --database-url and MigrationPilot opens one read-only connection to read pg_class, pg_stat_statements and pg_stat_activity. It reads no user data and runs no DDL.

That turns risk scoring from a guess into a measurement, and gives three rules the numbers they have nothing to say without: MP013 (DDL on a high-traffic table), MP014 (long-held locks on a table with millions of rows), MP019 (ACCESS EXCLUSIVE while connections are piling up).

Factor	Weight	Needs --database-url
Lock severity	0-40	No
Table size	0-30	Yes
Query frequency	0-30	Yes

GREEN is 0-24, YELLOW 25-49, RED 50-100.

Comparison

	MigrationPilot	Squawk	Atlas
Rules, all free	112	40	50+ analyzers, none free since v0.38
Auto-fix	20 rules	0	0
Cross-file sequence analysis	Yes	No	No
Real execution against ephemeral PG	Yes	No	Yes, needs Docker
MCP server for agents	Yes	No	No
Framework detection	14	0	0
Config presets	5	0	0
SARIF for Code Scanning	Yes	No	No
License	MIT	Apache-2.0 / MIT	Apache-2.0 core, no free lint

Squawk: 40 rules as of v2.62.0 (Aug 2026). Atlas moved migrate lint to Pro-only in v0.38 (Oct 2025) and later removed it from the Community Edition, so it could not be benchmarked without a paid account. The methodology records the exact command and its refusal.

Pricing

Everything the linter does is free and unmetered: all 112 rules including the production-context ones, auto-fix, sequence analysis, simulate, every output format, the GitHub Action, the MCP server. No account, no seat count, no telemetry, MIT.

The $499/year Org plan turns the free linter into an enforceable control: one signed policy across repositories, owner-attributed waivers that expire, and audit evidence for every merge.

Org plan · Full pricing

Architecture

src/
├── parser/ locks/         # libpg-query WASM, lock classification
├── rules/ fixer/          # 112 rules and the 20-rule auto-fixer
├── analysis/ scoring/     # shared pipeline, transaction boundaries, risk 0-100
├── sequence/ lockqueue/   # cross-file SQ rules, lock queue modelling
├── simulate/ mutate/      # PGlite execution, mutation-testing operators
├── cascade/ graph/ schema/ prediction/ templates/
├── production/ frameworks/ plugins/ output/ generator/
├── mcp/ action/ config/ hooks/ watch/ drift/ history/
├── policy/ auth/ license/ team/ audit/ billing/ usage/ doctor/
├── index.ts               # programmatic API, 69 value exports plus types
└── cli.ts                 # 24 commands

Programmatic API

import { analyzeSQL, allRules, parseMigration, classifyLock } from 'migrationpilot';

const result = await analyzeSQL(sql, 'migration.sql', 17, allRules);
console.log(result.violations, result.overallRisk);

Sixty-nine value exports plus full TypeScript types. allRules is the same rule set the CLI runs.

Development

pnpm install
pnpm test        # 1748 tests across 70 files
pnpm build       # CLI 1.4MB, Action 1.7MB, API 639KB, MCP 1.7MB
pnpm lint && pnpm typecheck
pnpm dev analyze path/to/migration.sql

CONTRIBUTING.md · SECURITY.md · CHANGELOG.md

License

MIT