qail

Schema-first database toolkit — Pull, diff, migrate, validate.

[!CAUTION] Release Candidate: QAIL is now in the release-candidate phase. The API is near-stable and battle-tested in production. Breaking changes are expected to be rare and limited to critical correctness/security fixes before 1.0.

Installation

cargo install qail

Commands

Schema Operations

# Extract schema from database
qail pull postgres://user:pass@host/db -o schema.qail

# Compare two schemas
qail diff old.qail new.qail

# Check best practices
qail lint schema.qail

# Format QAIL files
qail fmt schema.qail

Migration Operations

# Create a new migration
qail migrate create add_users_table --author "dev"

# Preview migration SQL
qail migrate plan old.qail:new.qail

# Apply migrations
qail migrate up old.qail:new.qail postgres://...

# Rollback migrations
qail migrate down postgres://...

Query REPL

# Interactive query transpiler
qail repl

> get users fields id, name where active = true
SELECT id, name FROM users WHERE active = true

SQL String vs SQL Bytes

• qail repl shows SQL text for inspection/debugging.
• Runtime execution with qail-pg is AST-first and protocol-byte based.
• In other words: SQL text is a tooling view here, not the required authoring model for app code.

Schema Format

QAIL uses a concise, version-controlled schema format:

-- schema.qail
table users (
    id uuid primary key default gen_random_uuid(),
    email text not null unique,
    created_at timestamptz default now()
);

table orders (
    id uuid primary key,
    user_id uuid references users(id),
    total numeric(10,2)
);

Features

• Schema extraction — Pull live schemas from PostgreSQL
• Smart diffing — Detect additions, removals, modifications
• Impact analysis — Warn about breaking changes
• Foreign key validation — Ensure referential integrity
• Data-safe migrations — Preview SQL before applying
• Type-safe queries — Transpile QAIL to SQL

Ecosystem

License

Apache-2.0

🤝 Contributing & Support

We welcome issue reports on GitHub! Please provide detailed descriptions to help us reproduce and fix the problem. We aim to address critical issues within 1-5 business days.