Korede Aderele Korede-TA

How to use check constraints with Knex.js and Postgres

Check constraints are useful for validating INSERT and UPDATE queries. With Knex.js, you have to use raw calls to add or drop constraints.

Add a constraint to check that my_column in my_table is at least 0:

knex.schema.raw(`
  ALTER TABLE
    my_table
 ADD CONSTRAINT

‪“‬In what way is JS any more maintainable than CSS? How does writing CSS in JS make it any more maintainable?”

‪Happy to chat about this. There’s an obvious disclaimer that there’s a cost to css-in-js solutions, but that cost is paid specifically for the benefits it brings; as such it’s useful for some usecases, and not meant as a replacement for all workflows. ‬

‪(These conversations always get heated on twitter, so please believe that I’m here to converse, not to convince. In return, I promise to listen to you too and change my opinions; I’ve had mad respect for you for years and would consider your feedback a gift. Also, some of the stuff I’m writing might seem obvious to you; I’m not trying to tell you if all people of some of the details, but it might be useful to someone else who bumps into this who doesn’t have context)‬

So the big deal about css-in-js (cij) is selectors.

import Data.Functor.Yoneda
import Data.Char
import Data.Kind

infixr 5
  ·

type  List :: (Type -> Type) -> Constraint
class List f where

Non-standard operators I use :) linked to from my twitter profile

I use kind synonyms

type T   = Type
type TT  = T -> T
type TTT = T -> TT
type C   = Constraint
type TC  = T -> C

gif-from-tweet

There are so many great GIFs out there and I want to have copies of them. Twitter makes that harder than it should be by converting them to MP4 and not providing access to the source material. To make it easier, I made a bash pipeline that takes a tweet URL and a filename, extracts the MP4 from that tweet and uses ffmpeg to convert back to GIF.

Dependencies

ffmpeg
- macOS: brew install ffmpeg
- Ubuntu/Debian: apt install ffmpeg

Set up an Upspin server backed by Google Drive

Overview

The purpose of this document is to explain how to deploy an Upspin server on a Debian or Ubuntu based machine - which can be a Raspberry Pi - and, optionally, use Google Drive to back the data.

Effectively, this will give you all the nifty advantages Upspin gives you in terms of file sharing without requiring a costly server.

	const http = require("http");
	const net = require("net");

	const server = http.createServer((req, res) => {
	req.resume();
	res.end("hello");
	});

	server.keepAliveTimeout = 6 * 1000;
	server.headersTimeout = 4 * 1000;

Service	Type	Storage	Limitations
Amazon DynamoDB	⚠️ Proprietary NoSQL	25 GB	⚠️ Payment method required
Amazon RDS	⚠️ Proprietary RDBMS		⚠️ Only free for 1 year
Azure SQL Database	MS SQL Server		⚠️ Only free for 1 year
👉 Clever Cloud	PostgreSQL, MySQL, MongoDB, Redis	256 MB (PostgreSQL)	Max 5 connections (PostgreSQL)

	const hash = require('easy-crypto/hash');

	class MerkleTreeNodeGeneric {
	compare(node) {
	return this.hash === node.hash;
	}
	}

	class MerkleTreeChildNode extends MerkleTreeNodeGeneric {
	constructor(data) {