Question 1

How to set up Memento for disk persistence in Elixir?

Accepted Answer

You need to stop Memento, create a schema on disk for specific nodes, restart, and create tables with disc_copies options. The README provides a code example but notes it's a manual process that should be done once, not automatically on startup.

Question 2

Memento vs Amnesia: which is better for modern Elixir?

Accepted Answer

Memento is designed for Elixir 1.7+ and avoids dependencies, while Amnesia has compilation issues in newer Elixir versions. Memento is lighter and more focused, but Amnesia might have more features if compatibility isn't a concern.

Question 3

Can Memento handle large datasets efficiently?

Accepted Answer

Memento leverages Mnesia's real-time performance for in-memory operations and distributed queries, but for very large datasets, the lack of advanced indexing or query optimization might limit efficiency compared to specialized databases.

Question 4

What are the limitations of Memento compared to PostgreSQL?

Accepted Answer

Memento lacks SQL support, complex transactions, foreign keys, and robust tooling for backups. It's best for lightweight, embedded use where data-code coupling is acceptable, not for external access or complex relational models.

Question 5

How to perform complex queries in Memento?

Accepted Answer

Use the select/3 method with MatchSpec guards for conditions, but it's limited to simple comparisons. For more complex logic, you might need to fall back to raw Mnesia calls or pre-process data in Elixir.

Question 6

Is Memento suitable for production use?

Accepted Answer

Yes, for specific cases like distributed, real-time applications where Mnesia's strengths align. However, the manual setup and missing migration tools require careful planning and testing for production deployments.

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