majackson

Django Migrations without Downtime

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

Adding Fields or Tables

Adding a (nullable) field or a new table

1. Make the model or column addition in your code.
2. Generate the model-change migrations locally.
3. Make two separate pull requests, one containing the model change, one containing the newly-generated migrationst. Note that the model-change migration should only contain the model change code, not any supplemental code using the newly-structured model.

majackson

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

1. Make the model or column addition in your code.

majackson

from django.contrib import admin


class ArrayFieldListFilter(admin.SimpleListFilter):
    "Admin-filterable field for an ArrayList"

    def __init__(self, request, params, model, model_admin):
        self._choices = model._meta.get_field(self.parameter_name).base_field.choices
        super(ArrayFieldListFilter, self).__init__(request, params, model, model_admin)

majackson

import json

class JsonListFile(object):
    """Class providing methods and context manager to read and write list-based
    json documents.
    This class will write out to the file on each append (maybe, os-dependent), 
    eliminating the need to hold the entire json object in memory before writing 
    (as is necessary with the plain stdlib json module).
    Primitive, but useful."""
                

majackson

javascript:fs=document.getElementsByTagName('form'); for (f=0;f<fs.length;f++) { f.setAttribute('novalidate', 'novalidate') }