Gleam PGO

A PostgreSQL database client for Gleam, based on PGO.

import gleam/pgo
import gleam/dynamic
import gleeunit/should

pub fn main() {
  // Start a database connection pool.
  // Typically you will want to create one pool for use in your program
  let db = pgo.connect(pgo.Config(
    ..pgo.default_config(),
    host: "localhost",
    database: "my_database",
    pool_size: 15,
  ))

  // An SQL statement to run. It takes one int as a parameter
  let sql = "
  select
    name, age, colour, friends
  from
    cats
  where
    id = $1"

  // This is the decoder for the value returned by the query
  let return_type = dynamic.tuple4(
    dynamic.string,
    dynamic.int,
    dynamic.string,
    dynamic.list(dynamic.string),
  )

  // Run the query against the PostgreSQL database
  // The int `1` is given as a parameter
  let assert Ok(response) = 
    pgo.execute(sql, db, [pgo.int(1)], return_type)

  // And then do something with the returned results
  response.count
  |> should.equal(2)
  response.rows
  |> should.equal([
    #("Nubi", 3, "black", ["Al", "Cutlass"]),
  ])
}

Installation

gleam add gleam_pgo

Atom generation

Creating a connection pool with the pgo.connect function dynamically generates an Erlang atom. Atoms are not garbage collected and only a certain number of them can exist in an Erlang VM instance, and hitting this limit will result in the VM crashing. Due to this limitation you should not dynamically open new connection pools, instead create the pools you need when your application starts and reuse them throughout the lifetime of your program.