pg module

Learn PostgreSQL connection with the pg module.

What is the pg module?

pg is the most popular PostgreSQL client module for Node.js. It offers both a single connection (Client) and a connection pool (Pool). Install: npm install pg.

PostgreSQL is a powerful open-source relational database. The pg module runs SQL queries as parameterized statements; this is the basic protection against SQL injection. The Pool reuses connections to boost performance; it does not open a new connection per request.

Client and Pool

pg offers two connection models. A Client is a single connection; it is handy for short scripts. A Pool is a connection pool; it is preferred in web servers.

The Pool opens several connections up front and distributes them to requests. You create it with const pool = new Pool({ connectionString: "..." }). Query: pool.query("SELECT * FROM users"). Each query borrows a connection from the pool and returns it when done. This reduces the cost of opening and closing connections.

Exercise Log the type of Pool

Import the Pool class from pg. Log typeof Pool.

Show example solution

const { Pool } = require("pg");
console.log(typeof Pool);

Test yourself

Which database does the pg module connect to?
- MongoDB
- MySQL
- PostgreSQL
- SQLite
Show answer

PostgreSQL — The pg module connects to PostgreSQL.

Complete the module name

const { Pool } = require("____")

Show answer

const { Pool } = require("pg")

Match each piece to its role

pg

PostgreSQL client
Pool

Connection pool
Client

Single connection
pool.query

Runs a query

Next lesson: Pool

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