It’s really hard to make a really good ORM.
Except rails ActiveRecord there is probably no one.
Even though AR also has some issues.
Except rails ActiveRecord there is probably no one.
Even though AR also has some issues.
Also it's maybe notably by a (former?) maintainer of ActiveRecord, though, I haven't really used RoR but I think the design is probably quite different - Diesel is very much just the SQL with a veneer of Rust, almost FFI wrapper like.
Why should I have to remember to use '.values' instead of 'GROUP BY'; '.filter'/'.except' instead of 'SELECT'? It's not helpful. I frequently have a clearer idea of the SQL I want (I'm certainly no DB expert) and have to make it at least twice as long, install a plugin, or in some cases just can't mangle it into Django. For what?
If you want to do something more OLAP-ish or insert data in bulk, you have a huge problem. SQLAlchemy is far better, even though SQLAlchemy also has its own share of limitations (dealing with jsonb_to_recordset and functions like it for example).
This is a problem, because there is a real boundary, typically including a network round trip. I've been on way too many projects where ORM-using code would pull some stuff from the database, do some application logic to filter or process the results, then loop and do another query for each result. Instead of doing it in the database query itself using joins (and possibly being able to use indexes for the filtering).
Even when people are very disciplined about this, I find that once you get to non-trivial queries, they become a lot harder to read in ORM code. I tend to have to think in terms of SQL, then translate between that and the ORM code on the fly. Its not so easy.
Sure, you could say all the teams I've ever worked on that did stuff like this are just bad at using ORM's, but after a few experiences like this on different teams, in different companies, with different developers, its time to stop blaming the people and maybe take another look at the tools.
There is just no good ORMs out there.
Except ActiveRecord (and maybe mongoose for mongo). And even these 2 are not the best choice for all use cases.
He has a lot of info on high performance Hibernate and particularly the n + 1 issue.
It should be mostly avoidable.
For anyone else interested, here’s one post he has on the problem: https://vladmihalcea.com/n-plus-1-query-problem/
I haven't been there for a while but I'm fairly sure there should be a few more.
Some would say this makes them a bad abstraction, but to me, data mapping is going to have to happen somewhere, and I would rather be building on someone else's work to write the data mapping for my applications than do it from scratch. You have to know when the ORM is the right tool to use, and when to drop into plain SQL for your querying, because they do not eliminate the need to write SQL, just reduce it significantly.