import { Pool } from "https://deno.land/x/postgres@v0.17.1/mod.ts";
Connection pools are a powerful resource to execute parallel queries and save up time in connection initialization. It is highly recommended that all applications that require concurrent access use a pool to communicate with their PostgreSQL database
import { Pool } from "./pool.ts";
const pool = new Pool({
database: "database",
hostname: "hostname",
password: "password",
port: 5432,
user: "user",
}, 10); // Creates a pool with 10 available connections
const client = await pool.connect();
await client.queryArray`SELECT 1`;
client.release();
You can also opt to not initialize all your connections at once by passing the lazy
option when instantiating your pool, this is useful to reduce startup time. In
addition to this, the pool won't start the connection unless there isn't any already
available connections in the pool
import { Pool } from "./pool.ts";
// Creates a pool with 10 max available connections
// Connection with the database won't be established until the user requires it
const pool = new Pool({}, 10, true);
// Connection is created here, will be available from now on
const client_1 = await pool.connect();
await client_1.queryArray`SELECT 1`;
client_1.release();
// Same connection as before, will be reused instead of starting a new one
const client_2 = await pool.connect();
await client_2.queryArray`SELECT 1`;
// New connection, since previous one is still in use
// There will be two open connections available from now on
const client_3 = await pool.connect();
client_2.release();
client_3.release();
Constructors
Methods
This will return a new client from the available connections in the pool
In the case of lazy initialized pools, a new connection will be established with the database if no other connections are available
import { Pool } from "./pool.ts";
const pool = new Pool({}, 10);
const client = await pool.connect();
await client.queryArray`UPDATE MY_TABLE SET X = 1`;
client.release();
This will close all open connections and set a terminated status in the pool
import { Pool } from "./pool.ts";
const pool = new Pool({}, 10);
await pool.end();
console.assert(pool.available === 0, "There are connections available after ending the pool");
await pool.end(); // An exception will be thrown, pool doesn't have any connections to close
However, a terminated pool can be reused by using the "connect" method, which will reinitialize the connections according to the original configuration of the pool
import { Pool } from "./pool.ts";
const pool = new Pool({}, 10);
await pool.end();
const client = await pool.connect();
await client.queryArray`SELECT 1`; // Works!
client.release();