Question 1

How does Ohm compare to ActiveRecord for Redis projects?

Accepted Answer

Ohm is lighter and tailored for Redis, offering fast performance without migrations, but it lacks ActiveRecord's rich ecosystem, migrations, and validation features. Use Ohm for simple Redis persistence and ActiveRecord for complex relational needs.

Question 2

How to implement many-to-many relationships in Ohm?

Accepted Answer

Use sets and references; for example, declare a set in one model and a reference in another, then manage associations with add/remove methods. The README shows this with events and participants sets.

Question 3

Does Ohm support database transactions?

Accepted Answer

Ohm relies on Redis' atomic operations for counters and sets, but doesn't provide multi-operation transactions out of the box. You need to use Redis' transaction commands directly if atomicity across multiple operations is required.

Question 4

Can I use Ohm with Ruby on Rails?

Accepted Answer

Yes, Ohm can be integrated into Rails as a standalone library for Redis persistence, but it won't replace ActiveRecord for SQL databases. You'll need to set up connections separately, as shown in the README examples.

Question 5

What are the performance benefits of using Ohm?

Accepted Answer

Ohm leverages Redis' in-memory storage and atomic operations, resulting in fast read/write speeds, especially for counters and set manipulations. This makes it ideal for real-time features like voting or tracking.

Question 6

How to handle data validation in Ohm models?

Accepted Answer

Ohm doesn't include built-in validation; you must implement it in Ruby code before saving objects or use extensions from Ohm Contrib for added functionality, which requires extra setup.

Question 7

Is Ohm good for large-scale applications?

Accepted Answer

Ohm scales well with Redis' performance, but its query limitations and memory constraints in Redis might require careful data modeling. For large datasets with complex queries, a hybrid approach with SQL might be better.

Ohm

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