sqlalchemy-alembic-expert-best-practices-code-review

What problem does it solve? Unsafe database migrations can lock tables, block writes, and cause downtime in production. This Skill provides opinionated rules for writing and reviewing SQLAlchemy ORM models and Alembic migrations so schema changes, indexes, and constraints are applied without blocking operations. ## Core Features & Use Cases - Concurrent Index Rules: Enforces postgresql_concurrently=True with autocommit blocks for all index creation and deletion. - Safe Constraint Patterns: Splits unique constraints, foreign keys, and check constraints into NOT VALID creation plus separate validation steps. - Multi-Step Column Type Changes: Guides column type migrations through add-column, backfill, and swap phases to avoid table rewrites. - Use Case: When reviewing a pull request that adds a unique constraint on a large users table, apply the unique-constraint rule to rewrite it as a concurrent unique index followed by a constraint using that index. ## Quick Start Review my Alembic migration and SQLAlchemy models for unsafe index, constraint, and column type change patterns.