Compare schemas and generate migration SQL.

dbdiff

Compare database schemas across environments and generate safe migration SQL — in one command.

Project website · All projects by rekurt

$ dbdiff postgres://prod/myapp postgres://staging/myapp

~ table: orders
  + column  paid_at        timestamptz NOT NULL DEFAULT now()
  + index   idx_orders_paid_at  ON orders(paid_at)
  - column  payment_date   varchar(32)

~ table: users
  + column  deleted_at     timestamptz

Generated migration → migration_20240406_143201.sql

Why dbdiff?

Most teams discover schema drift at the worst possible moment — right before a deploy. Existing tools either support only one database, require heavy setup, or can't compare a live DB against a .sql file.

dbdiff is a single binary that works anywhere CI runs.

• Zero dependencies — one static binary, no runtime, no Docker required
• DSN vs DSN or DSN vs SQL file — compare any two sources
• CI-native — non-zero exit code on drift, structured output, GitHub Actions support
• Safe migrations — warns about locking operations before you run them
• Multi-database — Postgres today, MySQL and SQLite on the roadmap

Install

Cargo:

cargo install dbdiff

Binary — download from Releases and put it in your $PATH:

# Linux (x86_64)
curl -sSL https://github.com/rekurt/dbdiff/releases/latest/download/dbdiff-x86_64-unknown-linux-musl.tar.gz | tar xz
sudo mv dbdiff /usr/local/bin/

# macOS (Apple Silicon)
curl -sSL https://github.com/rekurt/dbdiff/releases/latest/download/dbdiff-aarch64-apple-darwin.tar.gz | tar xz
sudo mv dbdiff /usr/local/bin/

From source:

git clone https://github.com/rekurt/dbdiff.git
cd dbdiff
cargo build --release
# Binary is at ./target/release/dbdiff

Usage

Compare two live databases

dbdiff postgres://user:pass@prod-host/myapp \
       postgres://user:pass@staging-host/myapp

Compare a live database against a schema file

dbdiff postgres://user:pass@prod-host/myapp --schema ./schema.sql

Useful during code review — verify that a migration file actually matches what's in production.

Compare MySQL databases

dbdiff mysql://user:pass@prod-host/myapp mysql://user:pass@staging-host/myapp

Compare a SQLite database against a schema file

dbdiff myapp.db --schema ./schema.sql

Save the generated migration to a file

dbdiff postgres://prod/myapp postgres://staging/myapp \
  --out migration.sql

CI mode — exit 1 if schemas differ

dbdiff postgres://prod/myapp postgres://staging/myapp --ci

Returns exit code 0 if schemas match, 1 if they differ. Use this in GitHub Actions, GitLab CI, or any pipeline.

Use a custom config file

dbdiff postgres://prod/myapp postgres://staging/myapp --config ./my-config.yml

JSON output for custom tooling

dbdiff postgres://prod/myapp postgres://staging/myapp --format json

GitHub Actions

Add schema drift detection to every PR:

# .github/workflows/schema-check.yml
name: Schema check

on: [pull_request]

jobs:
  schema-drift:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4

      - name: Install dbdiff
        run: |
          curl -sSL https://github.com/rekurt/dbdiff/releases/latest/download/dbdiff-x86_64-unknown-linux-musl.tar.gz | tar xz
          sudo mv dbdiff /usr/local/bin/

      - name: Check for schema drift
        env:
          PROD_DSN: ${{ secrets.PROD_DSN }}
          STAGING_DSN: ${{ secrets.STAGING_DSN }}
        run: dbdiff "$PROD_DSN" "$STAGING_DSN" --ci

What dbdiff detects

Locking warnings

Some ALTER operations lock the table on Postgres. dbdiff marks them explicitly:

⚠  ALTER TABLE orders ADD COLUMN paid_at timestamptz NOT NULL
   This operation will rewrite the table and acquire AccessExclusiveLock.
   Consider: ADD COLUMN ... DEFAULT NULL first, then backfill.

Configuration

Create .dbdiff.yml in your project root:

# .dbdiff.yml
ignore:
  tables:
    - _migrations
    - schema_version
  columns:
    - "*.created_at"   # ignore created_at in all tables
    - "sessions.*"     # ignore all columns in sessions table

output:
  format: pretty       # pretty | json | sql
  color: true

Supported databases

Feature flags

Database backends are optional and can be toggled via Cargo features:

# Install with only PostgreSQL support
cargo install dbdiff --no-default-features --features postgres

# Install with PostgreSQL and SQLite only
cargo install dbdiff --no-default-features --features postgres,sqlite

All backends (postgres, mysql, sqlite) are enabled by default.

Development

git clone https://github.com/rekurt/dbdiff
cd dbdiff
cargo build

# Run tests
cargo test

# Run with local SQL files
cargo run -- tests/fixtures/schema_a.sql --schema tests/fixtures/schema_b.sql

# Run with a local Postgres
docker run -d -p 5432:5432 -e POSTGRES_PASSWORD=pass postgres:16
cargo run -- postgres://postgres:pass@localhost/myapp --schema tests/fixtures/schema_b.sql

Project layout

src/
  main.rs          CLI entry point
  lib.rs           Library root
  cli.rs           Argument parsing (clap)
  model.rs         Schema / Table / Column / Index structs
  error.rs         Error types
  diff.rs          Schema comparison engine
  migration.rs     SQL migration generator
  output.rs        Terminal rendering (colored diff)
  config/
    mod.rs         Config file parsing (.dbdiff.yml)
    filter.rs      Schema filtering (ignore tables/columns)
  loader/
    mod.rs         Source dispatch logic
    postgres.rs    PostgreSQL introspection
    mysql.rs       MySQL / MariaDB introspection
    sqlite.rs      SQLite introspection
    sqlfile.rs     .sql file parser
tests/
  cli.rs           Integration tests
  config.rs        Config integration tests
  fixtures/        SQL test schemas + config fixtures

Contributing

Issues and PRs are welcome. Please open an issue before working on a large change.

For a new database driver, see src/loader/postgres.rs — implement a load function returning Schema and add detection logic in src/loader/mod.rs.

See CONTRIBUTING.md for full details.

License

MIT © Nikita