Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Python and Relational/Non-relational Databases
Search
Andrew Godwin
October 22, 2010
Programming
0
130
Python and Relational/Non-relational Databases
A talk I gave at PyCon Ukraine 2010.
Andrew Godwin
October 22, 2010
Tweet
Share
More Decks by Andrew Godwin
See All by Andrew Godwin
Reconciling Everything
andrewgodwin
1
320
Django Through The Years
andrewgodwin
0
210
Writing Maintainable Software At Scale
andrewgodwin
0
450
A Newcomer's Guide To Airflow's Architecture
andrewgodwin
0
360
Async, Python, and the Future
andrewgodwin
2
680
How To Break Django: With Async
andrewgodwin
1
730
Taking Django's ORM Async
andrewgodwin
0
730
The Long Road To Asynchrony
andrewgodwin
0
660
The Scientist & The Engineer
andrewgodwin
1
770
Other Decks in Programming
See All in Programming
OSS開発者という働き方
andpad
5
1.4k
TanStack DB ~状態管理の新しい考え方~
bmthd
2
360
AI時代に学習する意味はあるのか?
tomoyakamaji
0
100
Processing Gem ベースの、2D レトロゲームエンジンの開発
tokujiros
2
100
MCPで実現するAIエージェント駆動のNext.jsアプリデバッグ手法
nyatinte
7
980
Ruby Parser progress report 2025
yui_knk
1
220
Understanding Ruby Grammar Through Conflicts
yui_knk
1
180
あのころの iPod を どうにか再生させたい
orumin
2
2.5k
モバイルアプリからWebへの横展開を加速した話_Claude_Code_実践術.pdf
kazuyasakamoto
0
290
デザインシステムが必須の時代に
yosuke_furukawa
PRO
2
130
Trem on Rails - Prompt Engineering com Ruby
elainenaomi
1
100
Kiroの仕様駆動開発から見えてきたAIコーディングとの正しい付き合い方
clshinji
1
180
Featured
See All Featured
Design and Strategy: How to Deal with People Who Don’t "Get" Design
morganepeng
131
19k
Sharpening the Axe: The Primacy of Toolmaking
bcantrill
44
2.5k
How To Stay Up To Date on Web Technology
chriscoyier
790
250k
Building an army of robots
kneath
306
46k
Cheating the UX When There Is Nothing More to Optimize - PixelPioneers
stephaniewalter
284
13k
CoffeeScript is Beautiful & I Never Want to Write Plain JavaScript Again
sstephenson
161
15k
Site-Speed That Sticks
csswizardry
10
800
The Art of Delivering Value - GDevCon NA Keynote
reverentgeek
15
1.6k
RailsConf 2023
tenderlove
30
1.2k
Designing for Performance
lara
610
69k
Making Projects Easy
brettharned
117
6.3k
I Don’t Have Time: Getting Over the Fear to Launch Your Podcast
jcasabona
33
2.4k
Transcript
Relational / Non-relational Databases Python and Andrew Godwin
Introduction Python for 5 years Django core developer Data modelling
/ visualisation
""Andrew speaks English like a machine gun speaks bullets."" Reinout
van Rees
If I speak too fast - tell me!
What is a relational database?
A relational database is a “collection of relations”
It's what a lot of people are used to.
Relational Databases PostgreSQL MySQL SQLite
Let's pick PostgreSQL (it's a good choice)
Usage conn = psycopg2.connect( host="localhost", user="postgres" ) cursor = conn.cursor()
cursor.execute('SELECT * FROM users WHERE username = "andrew";') for row in cursor.fetchall(): print row
You've probably seen all that before.
Now, to introduce some non-relational databases
Document Databases MongoDB CouchDB
Key-Value Stores Redis Cassandra
Message Queues AMQP Celery
Various Others Graph databases Filesystems VCSs
Redis and MongoDB are two good examples here
Redis: Key-value store with strings, lists, sets, channels and atomic
operations.
Redis Example conn = redis.Redis(host="localhost") print conn.get("top_value") conn.set("last_user", "andrew") conn.inc("num_runs")
conn.sadd("users", "andrew") conn.sadd("users", "martin") for item in conn.smembers("users"): print item
MongoDB: Document store with indexing and a wide range of
query filters.
MongoDB Example conn = pymongo.Connection("localhost") db = conn['mongo_example'] coll =
db['users'] coll.insert({ "username": "andrew", "uid": 1000, }) for entry in coll.find({"username": "andrew"}): print entry
These all solve different problems - you can't easily replace
one with the other.
""When all you have is a hammer, everything looks like
a nail"" Abraham Manslow (paraphrased)
JOIN - your best friend, and your worst enemy.
Denormalising your data speeds up reads, and slows down writes.
Schemaless != Denormalised
Atomic operations are nice. conn.incrby("num_users', 2)
But SQL can do some of them. UPDATE foo SET
bar = bar + 1 WHERE baz;
Redis, the datastructures server. SETNX, GETSET, EXPIRES and friends
Locks / Semaphores conn.setnx("lock:foo", time.time() + 3600) val = conn.decr("sem:foo")
if val >= 0: ... else: conn.incr("sem:foo")
Queues conn.lpush("myqueue", "workitem") todo = conn.lpop("myqueue") (or publish/subscribe)
Priority Queues conn.zadd("myqueue", "handle-meltdown", 1) conn.zadd("myqueue", "feed-cats", 5) todo =
conn.zrange("myqueue", 0, 1) conn.zrem(todo)
Lock-free linked lists! new_id = "bgrdsd" old_end = conn.getset(":end", new_id)
conn.set("%s:next" % old_end, new_id)
Performance-wise, the less checks/integrity the faster it goes.
Maturity can sometimes be an issue, but new features can
appear rapidly.
You can also use databases for the wrong thing -
it often only matters ""at scale""
But how does this all relate to Python?
Most databases - even new ones - have good Python
bindings
Postgres: PsycoPG2 Redis: redis-py MongoDB: pymongo (and more - neo4j,
VCSen, relational, etc.)
Some databases have Python available inside (Postgres has it as
an option)
Document databases map really well to Python dicts
You may find non-relational databases a nicer way to store
state - for any app
Remember, you might still need transactions/reliability. (Business logic is probably
better off on mature systems for now)
Overall? Just keep all the options in mind. Don't get
caught by trends, and don't abuse your relational store
Thanks. Andrew Godwin @andrewgodwin http://aeracode.org