Marcelo marcelofern

My Vim-related gists

Long-form

Django Migrations without Downtime

The following instructions describe a set of processes allowing you to run Django database migrations against a production database without having to bring the web service down.

Note that in the below instructions, migrations are all run manually at explicit points, and are not an automatic part of the deployment process.

Adding Fields or Tables

Adding a (nullable) field or a new table

Make the model or column addition in your code.

FWIW: I (@rondy) am not the creator of the content shared here, which is an excerpt from Edmond Lau's book. I simply copied and pasted it from another location and saved it as a personal note, before it gained popularity on news.ycombinator.com. Unfortunately, I cannot recall the exact origin of the original source, nor was I able to find the author's name, so I am can't provide the appropriate credits.

Effective Engineer - Notes

By Edmond Lau
Highly Recommended 👍
http://www.theeffectiveengineer.com/

What's an Effective Engineer?

Docker - How to cleanup (unused) resources

Once in a while, you may need to cleanup resources (containers, volumes, images, networks) ...

delete volumes

// see: https://github.com/chadoe/docker-cleanup-volumes

$ docker volume rm $(docker volume ls -qf dangling=true)

$ docker volume ls -qf dangling=true | xargs -r docker volume rm

When to use a specific tool

Brief list describing scenarios calling for specific tools.

Spark
If you have (larger-than-memory) petabytes of JSON/XML/CSV files, a simple workflow, and a thousand node cluster

Dask
If you have (larger-than-memory) 10s-1000s of gigabytes of binary or numeric data (e.g., HDF5, netCDF4, CSV.gz), complex algorithms, and a (single) large multi-core workstation

Customize Save In Django Admin Inline Form

Background

This is a common case in django ORM.

from django.db import models

class Author(models.Model):

	// create a bookmark and use this code as the URL, you can now toggle the css on/off
	// thanks+credit: https://dev.to/gajus/my-favorite-css-hack-32g3
	javascript: (function() {
	var styleEl = document.getElementById('css-layout-hack');
	if (styleEl) {
	styleEl.remove();
	return;
	}
	styleEl = document.createElement('style');
	styleEl.id = 'css-layout-hack';

	// create a bookmark and use this code as the URL, you can now toggle the css on/off
	// thanks+credit: https://dev.to/gajus/my-favorite-css-hack-32g3
	javascript: (function() {
	var elements = document.body.getElementsByTagName('*');
	var items = [];
	for (var i = 0; i < elements.length; i++) {
	if (elements[i].innerHTML.indexOf('* { background:#000!important;color:#0f0!important;outline:solid #f00 1px!important; background-color: rgba(255,0,0,.2) !important; }') != -1) {
	items.push(elements[i]);
	}
	}

	# -- coding: utf-8 --
	from django.contrib.auth.decorators import login_required
	from django.utils.cache import patch_response_headers
	from django.utils.decorators import method_decorator
	from django.views.decorators.cache import cache_page, never_cache
	from django.views.decorators.csrf import csrf_exempt


	class NeverCacheMixin(object):
	@method_decorator(never_cache)

	git branch -m old_branch new_branch # Rename branch locally
	git push origin :old_branch # Delete the old branch
	git push --set-upstream origin new_branch # Push the new branch, set local branch to track the new remote