Posted by ciconia 3 days ago
ORMs are just a layer of abstraction. Like any abstraction, they make some tradeoffs that can get you into some sticky situations like inefficient queries mentioned in the article.
But, if you understand the tradeoffs, you can use them for what they're good for (standardization & simplification & in-codebase schema definitions & so on) and usually drop down to SQL whenever there's a particularly necessary case.
For me I find it's an excellent step up from a plain SQL query builder (with an API such as `select(Foo).join(bar)`) as it lets me both effortlessly perform projections (one can write `(\e -> (e.foo, e.bar) <$> someQuery` to take a query producing rows of `E` and turn it into rows of 2-tuples built from two projected fields.
I wrote a bit about my Rust rewrite here: https://bensimms.moe/postgres-lateral-makes-quite-a-good-dsl...
1. the functional/immutable nature of Elixir makes read and writes much more explicit and there is no need to magically track deep mutations of nested objects to translate them back into UPDATE/INSERT queries
2. Elixirs support for lisp-like macros allows for an ergonomic embedded query languages that is syntax and schema checked, mirrors raw SQL really well and, frees you from string-oriented query building
3. the query builder DSL addresses one of the main weaknesses of SQL query statements not being composable
4. The automatic conversion between JOINed tables (on the DB side) and nested structs (on the Elixir side) is done on the right abstraction level to work reliable and and being explicit enough to generate predictable queries.
I make use of table-valued db functions (IMO the most underrated feature of relational DBs) to define virtual relations/tables. I implement a set of CRUD db functions per entity. Then, on the app side, I define (or generate) DTO types representing these virtual relations. Finally, I use a custom ORM I wrote myself, which defines a general and consistent storage API, to talk to the db functions, using the DTO types.
The advantages of this approach are numerous, some include:
- I have full control of the SQL that goes into constructing the virtual table, I can leverage all the goodness of SQL here. I can even define multiple virtual relations per physical table, or read-only relations, etc, all by implementing the appropriate sets of CRUD db functions
- On the ORM side, I have all the goodness of static typing, a consistent API for all CRUD methods, a full fluent query DSL, etc
- Since, unlike tables or views, db functions can be passed arguments, i am able to layey all kinds of goodness on top of the basic CRUD actions, like audit info passing, custom upsert strategies, some level of record-based authorization, etc
But this architecture does require you to know and write SQL. IMO the value of ORMs do not lie in avoiding SQL; it lies in the capability to express consistent SQL at a higher level of abstraction, but you still need to understand your SQL.
ORMs that try to paper over all the differences fail miserably. They become super complicated and generally produce crap SQL.
ORMs also tend to oversimplify database design. They are just tables with primary keys, right? Who needs indices? Who needs to think about collation? God forbid anyone mentions physical organisation of the data!
Having said this, I do use a very small subset of SQLAlchemy (the bits I understand) in data pipelines.