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by fifilura 816 days ago
> you can print iteration by iteration the intermediate result

You would not be able to do that with a multi-threaded/multi-process application.

And this is the reason why e.g. Trino/Presto is so powerful together with SQL.

Instead of telling the computer how to go by to get your result, you tell it what result you want and let it do it in the best way.

The most up-front way of telling a computer "how" is a for-loop. And SQL does not have it. It may seem limiting, but avoiding explicit for loops gives the freedom to the computer. If it sees it fit to distribute that calculation over 200 distributed CPUs it can do that. With an imperative language you need to tell the computer exactly how it should distribute it. And from there it gets really hairy.
2 comments
whatever1 816 days ago
In development I don't need it to be multi-threaded. 1 thread is fine, as long as I can explain, step-by-step, how the calculations produced the output.
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fifilura 816 days ago
If you don't need threads in development OR production, you might as well do SELECT * from users and do the join in your imperative code.

If you need threads in production I think you will end up getting rid of your for loops anyway (or possibly, if you really want to, end up in a mutex/semaphore quagmire).

I must say, though, that there are other benefits with a declarative approach than just avoiding threading issues. But I guess it takes some getting used to.

I would say that the same "I cant step through my code" argument also goes for functional style code.

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Ma8ee 815 days ago
> If you don't need threads in development OR production, you might as well do SELECT * from users and do the join in your imperative code.

Except that it most likely will be orders of magnitude slower. Most databases are very good at what they are doing.

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fifilura 815 days ago
Yes. Kind of my point to. But the OP missed the possibility to step through the code.
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vrighter 814 days ago
sure you can. set the concurrency limit to 1. If you're debugging the logic and not some race condition then this works perfectly fine. Remember to profile afterwards though
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