LowFile-scopeRuby Plug & play

Use change_table for safer migrations

Group column/index changes with change_table; use concurrent indexes when needed.

Why this matters

Improves readability and can reduce lock duration.

Side-by-side examples engineers can pattern-match during review.

Avoid

add_column :users, :locale, :string
add_index :users, :locale

Prefer

change_table :users do |t|
  t.string :locale
end
add_index :users, :locale, algorithm: :concurrently

Bad

multiple scattered DDL calls

Good

change_table + concurrent index

From the same buckets as this rule.

Critical
Block risky database migrations (locking ops, downtime risk)
Review SQL/database migrations for operations that can lock large tables or cause downtime. Examples: creating indexes without CONCURRENTLY (Postgres), ALTER COLUMN TYPE on big tables, adding NOT NULL without backfill, long-running updates without batching. Require an online migration strategy (CONCURRENTLY, backfill in batches, dual-write/expand-contract) and a rollback plan.
migrations-backward-compatdatabase-query-performance
Critical
Deletion requests: anonymize or hard-delete PII irreversibly
On LGPD deletion, remove or irreversibly anonymize PII and purge dependent caches. Keep minimal audit metadata (timestamp, request ID) not linkable back to the subject.
compliance-lgpdmigrations-backward-compat+1
High
Add foreign key constraints in migrations
Enforce referential integrity with add_foreign_key and matching indexes.
database-query-performancemigrations-backward-compat