The Unit of Work Design Pattern Explained

In today's video, I'll explain the Unit of Work design pattern, a crucial concept for anyone who regularly interacts with databases. This pattern plays a key role by accumulating all transactions and executing them collectively. But why is this necessary? Find out this video.

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👀 Code reviewers:
- Yoriz
- Ryan Laursen
- Dale Hagglund
- Kit Hygh
- Alexander Milden
- Bean

🔖 Chapters:
0:00 Intro
0:41 What is the Unit of Work Pattern?
3:53 The Session Object as a Unit of Work
9:44 Benefits of Using the Unit of Work Pattern
11:43 Outro

#arjancodes #softwaredesign #python

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[NewQuietBear]

Interessant, ik heb ORM's gebruikt bijvoorbeeld en alhoewel ik nog niet bekend was met de onderliggende patronen, herken ik een hoop terug doordat ik deze packages ooit heb gebruikt.

[iamkaransethi]

I liked your calm and composed style of explaining a complex topic.Well done, your 3rd example made the most sense to me in terms of rollbacks scenario - IaC setup seems like a good place to use this design pattern. Thanks, Arjan!

[inhahe]

You asked about other ideas for use of the unit of work..one thing that came to mind was installing programs. All program installations seem to be able to roll back everything if the installation fails for some reason.

[avazart]

Session has method/contextmanager "begin" for control transaction.
SQLAlchemy has special mixin for using as dataclass "MappedAsDataclass" (for __str__/__repr__)

[spanomatic]

Unit of work is used in Guaranteed messaging between systems and applications (messaging middleware). send message and ack that sort of thing. Redis also has batch functions to perform several ops at once.

[uruzrune]

Would you consider doing a Saga Pattern video? Also, can you demonstrate using Saga and Unit of Work together to roll back a failed Saga?

[klmcwhirter]

Please take a look at the echo=True option to the create_engine function. This will ask sqlalchemy to output db interaction info including the sql statements being executed and more ...

Another great video. The UnitOfWork and Repository patterns are critical to building resilient, reliable persistence layers - and not just with db, but also filesystem, web service APIs, etc. !

[hcubill]

Excellent video! I had never heard of this, gives me good ideas how to change our code!

[aashayamballi]

can you please cover django concepts as well?

[edgeeffect]

My favourite ORM for PHP (sorry) uses UOW... so much nicer than those other Active Record ORMs. I did an extension that logged database changes to.... the database by scanning and extending the UOW on a commit... I had Python friends (I was doing JS) at my old job who used SQL Alchemy and I was always curious as to what was inside... now I really want to try it. UOW is my favorite underrated pattern - "boo!" to Active Record.

[jamesclarke]

As always thanks, could you maybe do one on django?

[hubstrangers]

Thank you....would be ideal scenario for embedded DBs (DuckDB, targeting scientific workloads, with specific pythonic libraries)

[obsidiansiriusblackheart]

I used to work for a PoS company and I accidentally implemented Unit of Work pattern without knowing it existed :) mine was a bit janky though, a dict of bools that was tracked between methods to know from which step we had to rollback

[BuFuO]

Do a coderoast of the nanogpt repo of Andrej Karpathy

[StarLord]

Do I need a different implementation of this pattern for each use-case in my domain?

[lucianop.]

This looks extremely similar to using an event queue. Throughout the lifetime of your program, you add events to a queue, and you delay their execution to a point where it is convenient (for any reason depending on context, in a game you might want to apply some filtering to change the order of events and process some before others), so it gives you full control on the order of execution. But, it can also help you to see which events failed, and then do the appropriate rollback.

EDIT: On second thought, it is an event queue, but used in a different context with (potentially) different intentions.