Migration Guard

The problem

Database migrations that work fine in development often lock tables, lose data, or break production during a rolling deploy. Standard CI catches syntax errors — it rarely catches a CREATE INDEX that freezes writes for ten minutes, or a RENAME that breaks the app version still running the old code.

What it does

• Reviews SQL, Flyway, and Liquibase migrations for Postgres, MySQL, and Oracle against ~48 dialect-specific safety rules.
• Flags blocking DDL (non-concurrent indexes, table rewrites, unvalidated constraints), data loss (DROP, TRUNCATE, UPDATE without WHERE), and zero-downtime hazards (RENAME, backfills, missing lock_timeout).
• Rewrites unsafe migrations into a safe, ordered sequence — expand-contract, batched backfills, two-step constraint validation — instead of just flagging the problem.
• Outputs text for local review, or JSON/SARIF for CI gates and GitHub code scanning.

Why it's worth having

These are well-known traps, but they're easy to miss in a normal code review — nobody reads a migration file thinking about ACCESS EXCLUSIVE locks on a 100M-row table. migration-guard encodes that expertise so your agent (and your CI) catches it every time, not just when someone remembers to check.

Example

ALTER TABLE orders ADD COLUMN status text NOT NULL; looks harmless. migration-guard flags it as a BLOCKER (forces a full-table rewrite under an exclusive lock) and rewrites it into three safe migrations: add the column nullable, backfill in batches, then enforce NOT NULL via a validated check.

Free vs full

A free edition covering BLOCKER-level lock and data-loss rules is available on GitHub. This full edition adds every CRITICAL/WARNING rule, the zero-downtime rewrite engine, MySQL support, and JSON/SARIF output for CI.