Clement Hoang clemmy

tmux shortcuts & cheatsheet

start new:

tmux

start new with session name:

tmux new -s myname

MySQL

Getting started

PSQL

Magic words:

psql -U postgres

Some interesting flags (to see all, use -h or --help depending on your psql version):

-E: will describe the underlaying queries of the \ commands (cool for learning!)
-l: psql will list all databases and then exit (useful if the user you connect with doesn't has a default database, like at AWS RDS)

(also know as lies and/or alternative facts)

js

setImmediate - doesn't set anything immediately, waits for a tick before executing
setTimeout(fn, n) - never sets the timeout to exactly n
Math.random() - computers cannot generate random numbers
Promise - is a lie when rejected
Array.reduce - accumulates, does not reduce (via @sbmadhav)

Migrations & Seeding

What are migrations??

Migrations are a way to make database changes or updates, like creating or dropping tables, as well as updating a table with new columns with constraints via generated scripts. We can build these scripts via the command line using knex command line tool.

To learn more about migrations, check out this article on the different types of database migrations!

	import { Component } from "React";

	export var Enhance = ComposedComponent => class extends Component {
	constructor() {
	this.state = { data: null };
	}
	componentDidMount() {
	this.setState({ data: 'Hello' });
	}
	render() {

	After automatically updating Postgres to 10.0 via Homebrew, the pg_ctl start command didn't work.
	The error was "The data directory was initialized by PostgreSQL version 9.6, which is not compatible with this version 10.0."

	Database files have to be updated before starting the server, here are the steps that had to be followed:

	# need to have both 9.6.x and latest 10.0 installed, and keep 10.0 as default
	brew unlink postgresql
	brew install [email protected]
	brew unlink [email protected]
	brew link postgresql