[feoren]

> What I generally want is:

> 1) Something translating SQL syntax into my native language, but maintaining SQL full semantics and expressiveness.

You have just described a good ORM used well.

> 2) This should allow me to be database-agnostic.

Meh, you sacrifice some powerful features if you demand total database agnosticism, and how often do you actually switch databases? Being database-agnostic is a side benefit of writing your logic simply against a good abstraction. The biggest benefit is composability. You can write (and optimize) one query against abstractions, and re-use that query in lots of different ways.

> 3) This should prevent things like injection attacks.

As all ORMs automatically already do.

> 4) It should not map onto objects. It should maintain 100% of the capability of SQL.

If it's not mapping onto objects, what is it doing? The problem is that your mental model of what "objects" means includes awful design decisions like deep inheritance trees, mutability, and lots of reference cycles (this.parent.child[0] == this, etc.) If your object model is already clean and following relational principles, then mapping into that model is exactly what you want.

It should not strive to maintain the capability of some bastardized pseudo-language which is despised by the progenitors of relational logic. It should strive to support the relational model. That's not the same thing.

> 5) This may and ideally should have added functionality, for example, around managing and organizing database migrations.

No, because your code versions and your database schemas advance together. To reliably run a database migration in code, you'd need to run it with the code version that exactly matches each step in the schema. That means for each step in the migration, you'd need to checkout the correct commit in git, compile, and run the ORM code in that version. Either that, or you're maintaining a code model that is compatible with every historical database schema, which is way worse.

But what ORMs should be able to do (and I haven't found one that does this well) is generate SQL migration scripts for you, which you store. Those would be frozen relative to the database schema version, so all the above problems go away.

> What most programmers fail to understand -- since universities don't teach -- is how powerful and elegant the underlying theory of databases is.

The underlying relational model is powerful and elegant. SQL itself is not. SQL is disliked by the founders of the relational model. Good ORMs let you incorporate the relational model into your code.

[blagie]

> You have just described a good ORM used well.

No. I did not. ORM is an "object–relational mapping." It maps data relations onto objects.

https://en.wikipedia.org/wiki/Object%E2%80%93relational_mapp...

> how often do you actually switch databases?

Very often. Virtually all of the systems I write have at least two back-ends to maintain that flexibility. At the very least, I'd like my systems to run well locally for development but also to scale. The easiest way to do that is to e.g. support both SQLite and Postgres, but there are other ways which make sense.

In proprietary settings, I like having a BATNA. The architectural flexibility means I get better prices on hosted services and aren't liable to turning into a cash cow through lock-in. That's savings even if I'm not switching.

> If your object model is already clean and following relational principles, then mapping into that model is exactly what you want.

This is where your thinking broke. A good object model is NOT a relational model, and a good relational model is NOT an object model.

Learn the theory of both. They're both good theories, but they're different.

An ORM makes sense if you want to use an object model, but want the backing store to be an RDBMS.

> But what ORMs should be able to do (and I haven't found one that does this well) is generate SQL migration scripts for you, which you store. Those would be frozen relative to the database schema version, so all the above problems go away.

I believe that's one instantiation of what I wrote: "This may and ideally should have added functionality, for example, around managing and organizing database migrations." It's actually exactly what I was thinking.

Some ORMs do this not badly, actually. Don't let the perfect be the enemy of the good. A simple system which does 90% of the work of generating a migration (with manual verification and tweaks) is often better than a complex one which tries to do 100% of the work.

> The underlying relational model is powerful and elegant. SQL itself is not. SQL is disliked by the founders of the relational model.

Citation required.

In either case, ORMs aren't translating just syntax, but also semantics. That's where the problem lies. If you're not doing that, you're not an ORM.

> Good ORMs let you incorporate the relational model into your code.

You're confused about what an ORM is. ORMs essentially map an RDBMS onto an object model (which an OODBMS does natively). The two models are fundamentally different. It's a translation layer.

Any good database library will let me "incorporate the relational model into my code." That's not an ORM.

[feoren]

You're being condescending, telling me to "learn the theory". We've clearly had different experiences and work with different kinds of systems. You're automatically discounting what I say by assuming I must be a newbie because I disagree with you. No. We both have things to learn from each other and you telling me "go RTFM, newbie" is shutting down that opportunity.

> Virtually all of the systems I write have at least two back-ends to maintain that flexibility.

It sounds like that's a worthwhile tradeoff for you, but it is a tradeoff, giving up some of the unique power of each individual database in order to support both. Realize that most people don't do this.

> A good object model is NOT a relational model, and a good relational model is NOT an object model.

Maybe this is our biggest disagreement. I believe there is a model that can get the biggest benefits of both. I'm not alone in this; papers in Software Engineering, "Out of the Tar Pit", prescribes this as a possible solution to a lot of woes in software engineering:

"The classical ways to approach the difficulty of state include object oriented programming which tightly couples state together with related behaviour, and functional programming which — in its pure form — eschews state and side-effects all together ... We argue that it is possible to take useful ideas from both and that — when combined with some ideas from the relational database world - this approach offers significant potential for simplifying the construction of large-scale software systems"

https://curtclifton.net/papers/MoseleyMarks06a.pdf

I agree with them: Object Oriented Programming alone is nice for UIs but otherwise has failed to live up to its hype; Functional Programming is elegant and pure but hard to actually get anything done with; the Relational Model is simple and powerful but writing an application entirely in database procedures is a Lovecraftian Horror. So look for a model that takes the best from all three, and apply that model -- at least conceptually -- in both your database design and your application code. It is actually possible, and it's wonderful. But it will piss off the zealots on both sides.

I'm not sure what you consider "a good object model", but there is very little agreement in our industry on what exactly that looks like. If yours permits the CS 101 inheritance examples like "Dog : Animal" then I'd strongly disagree with you. Or maybe yours is the Smalltalk message-passing version: better, but still not immune to improvement. Don't assume that everyone who doesn't 100% line-toe bog standard OOP and bog standard SQL RDMSes needs to "RTFM".

>> SQL is disliked by the founders of the relational model.

> Citation required.

"SQL isn’t just user hostile, it involves some very serious departures from relational theory ... Suffice it to say that those departures are so serious that I honestly believe SQL has no real right to be called relational at all." -- Chris Date, who worked closely with EF Codd and helped spread his ideas.

https://red-gate.com/simple-talk/opinion/opinion-pieces/chri...

[blagie]

Citations appreciated! I will not respond in-depth to most parts, because I agree with what you're writing. But I will make one or two points. To clarify a piece of confusion:

> Maybe this is our biggest disagreement. I believe there is a model that can get the biggest benefits of both. I'm not alone in this; papers in Software Engineering, "Out of the Tar Pit", prescribes this as a possible solution to a lot of woes in software engineering:

I don't necessarily disagree, Moseley does not describe an OO model. If you showed their proposal to someone who does e.g. just Java, they would puke.

> I'm not sure what you consider "a good object model", but there is very little agreement in our industry on what exactly that looks like

A more accurate statement is that there are many models. The very first one I learned formally was the Booch method, over a quarter-century ago. My productivity fell about tenfold when I began applying it. Second one was Java. Less than tenfold. Like you, I eventually rejected OO for most things other than UX, or relatively small objects which are more-or-less little more than data types.

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But onto the main point:

- Models have theoretical properties which work well in isolation.

- Mixing models often destroys those properties.

- For example, I can slice code vertically or horizontally. Either works well. If I mix the two, I have no abstraction or modularity left.

- Java got rid of MI for a reason. It's not that MI is bad, but it doesn't fit into the Java OO model.

- If I add a little bit of OO to functional, I get mutation, and almost all of the benefit disappears in a poof. (note: There are systematic ways to do this which maintain benefits of both)

- Aside from theoretical properties, models are a way to communicate. You know what to expect in code.

You can design hybrid models, but you can't just mix models. Code kinda falls apart. None of the OO models map cleanly onto relational, or vice-versa. It's possible to do other models that perhaps combine aspects of both, but they're no longer OO.

An ORM is a bastardization of the two models, by trying to mesh them together. In contrast, I like Moseley Marks a lot, which is it's own model.

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And a footnote: I no longer find it hard to get things done with functional programming. Most of my code is pretty close to pure functional, with a few well-controlled places with state (on the front-end, with Redux). Part of that is experience on my part, but part of that is that both Python and modern JavaScript surface many of the most useful aspects of functional in ways which are linguistically nice.

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As a second footnote: A lot of this is based on domain. For example, numerical code works great in functional, while as you pointed out, UX maps well onto OO.