Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Speaker Deck
PRO
Sign in
Sign up for free
Models and Migrations and Schemas - oh my!
Andrew Godwin
September 06, 2012
Programming
5
1.9k
Models and Migrations and Schemas - oh my!
A talk from DjangoCon US 2012 on South, Django, and schema migrations.
Andrew Godwin
September 06, 2012
Tweet
Share
More Decks by Andrew Godwin
See All by Andrew Godwin
A Newcomer's Guide To Airflow's Architecture
andrewgodwin
0
87
Async, Python, and the Future
andrewgodwin
1
360
How To Break Django: With Async
andrewgodwin
1
280
Taking Django's ORM Async
andrewgodwin
0
330
The Long Road To Asynchrony
andrewgodwin
0
380
The Scientist & The Engineer
andrewgodwin
1
370
Pioneering Real-Time
andrewgodwin
0
150
Just Add Await: Retrofitting Async Into Django
andrewgodwin
2
1.1k
Terrain, Art, Python and LiDAR
andrewgodwin
1
230
Other Decks in Programming
See All in Programming
ゴーファーくんと学ぶGo言語の世界/golang-world-with-gopher
iwasiman
1
140
microCMS × Shopifyで、ECサイトがリニューアル後急成長した話
microcms
0
450
Language Summit 2022: WebAssembly: Python in the browser and beyond
tiran
2
310
코드 품질 1% 올리기
pluu
1
900
From Java 11 to 17 and beyond
josepaumard
0
290
New Relicを使った Observabilityの実現方法と活用例 / gocon 2022 spring after talk
budougumi0617
0
940
roadmap to rust 2024
matsu7874
1
600
2022 Android Training
mixi_engineers
1
630
アプリのログをチーム外で活用してもらうためにやったこと
shotakashihara
0
120
Practical Advanced Kotlin in Practice
rock3r
3
130
【Qiita Night】新卒エンジニアによるSwift6与太予想
eiji127
0
110
heyにおけるSREの大切さ~マルチプロダクト運用の「楽しさ」と「難しさ」および今後の展望~
fufuhu
3
1.5k
Featured
See All Featured
jQuery: Nuts, Bolts and Bling
dougneiner
56
6.4k
Making the Leap to Tech Lead
cromwellryan
113
6.9k
JavaScript: Past, Present, and Future - NDC Porto 2020
reverentgeek
37
3.2k
A better future with KSS
kneath
225
15k
Adopting Sorbet at Scale
ufuk
63
7.5k
How to Ace a Technical Interview
jacobian
265
21k
Art, The Web, and Tiny UX
lynnandtonic
280
17k
How New CSS Is Changing Everything About Graphic Design on the Web
jensimmons
212
11k
Fight the Zombie Pattern Library - RWD Summit 2016
marcelosomers
226
15k
Writing Fast Ruby
sferik
612
57k
Why You Should Never Use an ORM
jnunemaker
PRO
47
5.5k
The Straight Up "How To Draw Better" Workshop
denniskardys
225
120k
Transcript
Models & Migrations & Models & Migrations & Schemas –
oh my! Schemas – oh my! Andrew Godwin Andrew Godwin @andrewgodwin @andrewgodwin flickr.com/anders_young flickr.com/anders_young
· Django core dev · Django core dev · South
· South · Lanyrd · Lanyrd
· The Past · The Past django-evolution, south 0.1 django-evolution,
south 0.1 · The Present · The Present south 0.7 south 0.7 · The Future · The Future django 1.6? south 2.0? django 1.6? south 2.0?
· The Past · The Past django-evolution, south 0.1 django-evolution,
south 0.1 · The Present · The Present south 0.7 south 0.7 · The Future · The Future django 1.6? south 2.0? django 1.6? south 2.0?
Databases hate schema changes Databases hate schema changes “ “All
that optimising gone to waste...” All that optimising gone to waste...” flickr.com/96dpi flickr.com/96dpi
· Locks whole tables · Locks whole tables · Hammers
disk I/O · Hammers disk I/O · Causes inconsistent results · Causes inconsistent results
There's a code/schema split There's a code/schema split Your database
is going to ignore git Your database is going to ignore git flickr.com/nataliejohnson flickr.com/nataliejohnson
· Extra fields are fine · Extra fields are fine
· Missing fields are not · Missing fields are not · Painful/slow to sync · Painful/slow to sync
django-evolution django-evolution dmigrations dmigrations
South 0.1 South 0.1
None
None
· South 0.2 · South 0.2 mysql support mysql support
· South 0.3 · South 0.3 dependencies dependencies
· South 0.4 · South 0.4 altering columns altering columns
SQLite SQLite
· South 0.5 · South 0.5 ORM freezing ORM freezing
Automatic change detection Automatic change detection
· South 0.6 · South 0.6 Field introspection Field introspection
Dependency solving speed Dependency solving speed
· South 0.7 · South 0.7 data/schema split data/schema split
missing defaults for NOT NULL missing defaults for NOT NULL multidb multidb custom fields ignored custom fields ignored
· The Past · The Past django-evolution, south 0.1 django-evolution,
south 0.1 · The Present · The Present south 0.7 south 0.7 · The Future · The Future django 1.6? south 2.0? django 1.6? south 2.0?
· Mostly stable · Mostly stable Core API hasn't changed
for 2 years Core API hasn't changed for 2 years
· No rebase/collapse · No rebase/collapse Needs a big change
to migration tracking Needs a big change to migration tracking
· Opaque migrations · Opaque migrations Impossible to peek inside
migrations Impossible to peek inside migrations
· The Past · The Past django-evolution, south 0.1 django-evolution,
south 0.1 · The Present · The Present south 0.7 south 0.7 · The Future · The Future django 1.6? south 2.0? django 1.6? south 2.0?
django.db.backends.schema django.db.backends.schema
· Database abstraction layer · Database abstraction layer Has no
idea migrations exist Has no idea migrations exist
from django.db import connection from django.db import connection editor =
connection.schema_editor() editor = connection.schema_editor() editor.start() editor.start() editor.create_model(Author) editor.create_model(Author) editor.create_model(Book) editor.create_model(Book) editor.commit() editor.commit()
from django.db import connection from django.db import connection editor =
connection.schema_editor() editor = connection.schema_editor() editor.start() editor.start() editor.alter_field( editor.alter_field( Book, Book, CharField(max_length=100, db_index=True), CharField(max_length=100, db_index=True), TextField(), TextField(), ) ) editor.delete_field(Author, ”age”) editor.delete_field(Author, ”age”) editor.commit() editor.commit()
github.com/andrewgodwin/ github.com/andrewgodwin/ django/tree/schema-alteration django/tree/schema-alteration
contrib. contrib.migrations migrations
· Migration creation/running · Migration creation/running Would replace South Would
replace South
· Declarative migrations · Declarative migrations Combinable, optimisable Combinable, optimisable
· No frozen ORM · No frozen ORM Derived from
the migration history Derived from the migration history
· Raw SQL support · Raw SQL support For those
with beards For those with beards
· SQL output support · SQL output support For those
with full-flowing beards For those with full-flowing beards
from migrations.api import * from migrations.api import * class Migration(BaseMigration):
class Migration(BaseMigration): actions = [ actions = [ CreateModel(name = "Author", fields = [ CreateModel(name = "Author", fields = [ ("name", ("name", Field( Field( "django.db.models.fields.CharField", "django.db.models.fields.CharField", [], {"max_length": "100"} [], {"max_length": "100"} )), )), ]) ]) ] ]
github.com/andrewgodwin/migrations/ github.com/andrewgodwin/migrations/ Incomplete and broken code! Incomplete and broken code!
south 1.0 south 1.0
· Python 3 support · Python 3 support To coincide
with Django 1.5 To coincide with Django 1.5
· Will require Python 2.6 · Will require Python 2.6
As otherwise Python 3 is a PITA As otherwise Python 3 is a PITA
All subject to change! All subject to change! This isn't
set in stone. This isn't set in stone.
· Feedback on schema-alt branch · Feedback on schema-alt branch
How to help How to help · Weird and wacky use cases · Weird and wacky use cases · Come talk to me during sprints · Come talk to me during sprints
Questions? Questions? Andrew Godwin / @andrewgodwin Andrew Godwin / @andrewgodwin
flickr.com/oimax flickr.com/oimax