Locates SQL template strings and schema definitions in your code. Evaluates the queries, matching them against your database schema. Supports type-checking via TypeScript, so you get statically typed SQL queries validated against your database schema 😱😱

Use with squid. It provides SQL tagged template strings, auto-escapes dynamic expressions to prevent SQL injections and comes with some syntactic sugar to write short, explicit SQL queries.

🦄  Validates SQL template strings in code 🚀  Checks SQL queries syntax and semantics ⚡️  Works statically, without additional runtime overhead ⚙️  Built on top of Babel & TypeScript 🛠  Uses libpg_query, the actual Postgres SQL parser

Installation

npm install --save-dev postguard

# or using yarn:
yarn add --dev postguard

CLI

Run the tool like this:

postguard src/models/*

We can use npm's npx tool to run the locally installed package:

npx postguard src/models/*

Command line options

Usage
  $ postguard ./path/to/source/*.ts

Options
  --help        Print this help
  -w, --watch   Watch files and re-evaluate on change

Guide

• Usage - Hands-on examples how to use the tool
• Validations - List of validations that will be performed

Motivation

Let's quickly compare the options you got when writing code that uses a relational database.

Our sample use case is updating project rows that are owned by a certain user.

Plain SQL

Sample:

const { rows } = await database.query(`
  UPDATE projects SET
    last_opened = NOW(),
    open_count = open_count + 1
  WHERE
    projects.id IN (
      SELECT project_id FROM project_members WHERE user_id = $1
    )
  RETURNING *
`,
  [ userId ]
)

Pro:

• Efficient queries
• Explicit - No magic, full control
• Functional stateless data flow, atomic updates

Con:

• Very easy to make mistakes
• No way of telling if correct unless code is run
• Can be quite verbose
• Requires knowledge about SQL & your database
• No type safety

ORMs (Sequelize, TypeORM, ...)

Sample:

// (Model definitions not included)

const user = await User.findById(userId)
const projects = await user.getProjects()

const updatedProjects = await Promise.all(
  projects.map(async project => {
    project.last_opened = new Date(Date.now())
    project.open_count++
    return project.save()
  })
)

Pro:

• Easy to get started
• Type-safety
• Less error-prone than writing raw SQL
• Requires no SQL knowledge

Con:

• Implicit - Actual database queries barely visible
• Usually leads to inefficient queries
• Update operations based on potentially stale local data
• Virtually limits you to a primitive subset of your database's features

Query builder (Knex.js, Prisma, ...)

Sample:

// (Model definitions not included)

const usersProjects = await prisma.user({ id: userId }).projects()

const updatedProjects = await Promise.all(
  projects.map(project =>
    prisma.updateProject({
      data: {
        last_opened: new Date(Date.now()),
        open_count: project.open_count + 1
      },
      where: {
        id: project.id
      }
    })
  )
)

Pro:

• Explicit - Full control over queries
• Functional stateless data flow
• Type-safety

Con:

• Additional abstraction layer with its own API
• Atomic updates still hardly possible
• Requires knowledge about both, SQL & your database plus the query builder API

SQL with squid & postguard 🚀

Sample:

// (Schema definition not included)

const { rows } = await database.query<ProjectRecord>(sql`
  UPDATE projects SET
    last_opened = NOW(),
    open_count = open_count + 1
  WHERE
    projects.id IN (
      SELECT project_id FROM project_members WHERE user_id = ${userId}
    )
  RETURNING *
`)

Pro:

• Explicit - Full control, no implicit magic
• Fast due to absence of abstraction layers
• Functional stateless data flow, atomic updates
• Full query validation at build time
• Type-safety

Con:

• Requires knowledge about SQL & your database

Debugging

Set the environment variable DEBUG to postguard:* to enable debug logging. You can also narrow debug logging down by setting DEBUG to postguard:table or postguard:query, for instance.

Questions? Feedback?

Feedback is welcome, as always. Feel free to comment what's on your mind 👉 here.

License

MIT