metainfa

Postgres Distributed Key Generation

This SQL creates a Postgres function to generate sequential, numeric, unique IDs in a consistent format across services. Useful for database sharding or microservices.

Draws heavily on Instagram's ID generator, via Rob Conery, with minor modifications.

The main changes are that the unique number resolution is per-second rather than per-millisecond. This is to reduce key size below 2^53^-1 so that generated IDs that are under Javascripts Number.MAX_SAFE_INTEGER limit . This is important if you're using these on a Node.js server (e.g. our use case is an Express API using Hashids).

Max IDs are in the order of 51 bits, broken down as follows:

31 bits for the timestamp difference

PostgreSQL JSON Cheatsheet

Using JSON in Postgres by example.

Quick setup via Docker

Download and install: Docker Toolbox
Open Docker Quickstart Terminal
Start a new postgres container:
docker run --name my-postgres -e POSTGRES_PASSWORD=mysecretpassword -d postgres

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)

	/**
	Proof-of-concept server-sent events HTTP server using Node.js and RxJS

	Open http://localhost:8000 in a browser and view the console.
	**/
	var http = require('http'),
	https = require('https');

	var Rx = require('rx');

	<html>
	<head>
	<script src='http://code.jquery.com/jquery-1.5.1.min.js'></script>
	</head>

	<body>
	<h2>Naive canvas</h2>
	<canvas id="naive" width="400" height="50"></canvas>

	<h2>High-def Canvas</h2>

	import React from 'react'
	import { render } from 'react-dom';
	import { Router, Route } from 'react-router-dom';
	import LazyRoute from 'lazy-route';

	const App = () => {
	render() {
	return (
	<Router>
	<Route

	CREATE OR REPLACE FUNCTION notify_trigger() RETURNS trigger AS $$
	DECLARE
	channel_name varchar DEFAULT (TG_TABLE_NAME \|\| '_changes');
	BEGIN
	IF TG_OP = 'INSERT' THEN
	PERFORM pg_notify(channel_name, '{"id": "' \|\| NEW.id \|\| '"}');
	RETURN NEW;
	END IF;
	IF TG_OP = 'DELETE' THEN
	PERFORM pg_notify(channel_name, '{"id": "' \|\| OLD.id \|\| '"}');

	#!/bin/bash
	set -eu
	_UID=$(id -u)
	GID=$(id -g)

	# give lxd permission to map your user/group id through
	grep root:$_UID:1 /etc/subuid -qs \|\| sudo usermod --add-subuids ${_UID}-${_UID} --add-subgids ${GID}-${GID} root

	# set up a separate key to make sure we can log in automatically via ssh
	# with $HOME mounted

	; Autohotkey Capslock Remapping Script
	; Danik
	; More info at http://danikgames.com/blog/?p=714
	; danikgames.com
	;
	; Functionality:
	; - Deactivates capslock for normal (accidental) use.
	; - Hold Capslock and drag anywhere in a window to move it (not just the title bar).
	; - Access the following functions when pressing Capslock:
	; Cursor keys - J, K, L, I

	// vscode-keybindings for navigation with I/J/K/L and additional functionality with surrounding characters

	// Place your key bindings in this file to overwrite the defaults
	// ALT + I/J/K/L: up/left/down/right
	// ALT + SHIFT + I/J/K/L: mark text up/left/down/right
	// CTRL + J/L: send cursor to start/end of line
	// CTRL + ALT + J/L: send cursor to start/end of word
	// CTRL + ALT + U/O: send cursor to "wordPartLeft"/"wordPartRight"
	// CTRL + ALT + SHIFT + U/O: mark from cursor to "wordPartLeft"/"wordPartRight"
	// CTRL + ALT + Y: got to declaration