For those who don't follow PHP closely - that version was an attempted refactor of the string implementation which essentially shut down nearly all work on PHP for a decade, stagnating the language until it became pretty terrible compared to other options. They finally gave up and started work on PHP 7 which uses the (perfectly good) PHP 5 strings.
Ten years of wasted time by the best internal PHP developers crippled the project - I'm amazed it survived at all.
On the other hand, there's also the case of the Lunar Module guidance software that was hard-coded to run exactly every two seconds. If the previous subroutine call was still running when the next one was due, the previous one was harshly terminated (with weird side effects).
One of the main programmers suggested making it so that the next guidance routine wouldn't run until the previous one was done. This would make the code less sensitive to race conditions and allow more useful functionality for the pilots (who were the actual users and did seem to want it). However everyone assumed the two-second constant was implicitly embedded everywhere.
It wasn't -- only in a few places -- and with that fixed the code got more general and the proof of concept ran better than ever in about every simulator available. The amount of control it gave pilots was years ahead of the curve. But it never got a chance to fly on a real mission because what was there was "good enough" and nobody bothered to try.
In our combined comments there's a lesson about growing experiments and figuring out how to achieve failure quickly.
I think this is a great article that takes a maximalist point and that’s its flaw.
You should rewrite code only when the cost of adding a new feature (one that is actually necessary) to the old codebase becomes comparable to designing your entire system from scratch to allow for that feature to be added easily. That is to say that the cost of the rewrite should become comparable to the cost of continuing development. I have been a part of a couple of rewrites like that, one of them quite complex, and yes they were warranted and yes they worked.
But having said that you should absolutely be conservative with rewriting code. It’s a bad habit to always jump to a rewrite.
I think it’s very dependent on how you use words like “rewrite” or “refactor”. The point the author makes about the two page function, and all the bug-fixes (lessons learned) makes sense only if you “rewrite” from scratch without looking at the history. You can absolutely “rewrite” the function in a manner that is “refactoring”, but will often get called “rewrite” in the real world. This may be because “refactor” is sort of this English CS term that doesn’t have a real translation or usage in many languages and “rewrite” is sort of universal for changing text, but in CS is sort of “rebuilding” things.
I don’t think you necessarily need to be conservative about rewriting things. We do it all the time in fact. We build something to get it out there and see the usage, and then we build it better and then we do it again. Which often involves a lot of “rewriting” but thanks to principles like SOLID’s single responsibility makes this rather easy to both do and maintain (we write a lot of semi-functional code and try to avoid using OOP unless necessary, so we don’t really use all the parts of SOLID religiously).
I do agree that it’s never a good idea to get into things with the mind-set of “we can do this better if we start from scratch” because you can’t.
There's currently a trend towards shitting on microservices-everything, imo largely justified. But missing from that is that identifying a logical feature and moving it to a microservice is one of the safer ways to begin a gradual rewrite of a critical system. And usually possible to get cross-dept buyin for various not always wholesome reasons. It may not always be the best technical solution but it's often the best political one when a rewrite is necessary.
>identifying a logical feature and moving it to a microservice is one of the safer ways to begin a gradual rewrite of a critical system
Why not identify that same logical feature and move it into a library. How does a Microservice add value here?
Identifying, extracting and adding tests to logical features has been the sane way to rewrite software for ages. Michael feathers even wrote a book about it [1]. This ship of theseus approach works because it's incremental and allows for a complete rewrite without ever having non-functional software in between.
Adding a REST/networking/orchestration boundary to make it a Microservice just for the sake of extracting it adds a lot of complexity for no gain.
Microservice can be the right architecture, but not if all you want is to extract a library.
Process isolation affects so many things in C. The strategy change is going to require changes to so many modules that it will either be a re-write or buggy.
In practical terms, if every line needs to be audited and updated, it is a re-write
What makes you think that it will require that many changes? There will be some widespread mechanical changes (which can be verified to be complete with a bit of low level work, like a script using objdump/nm to look for non-TLS mutable variables) and some areas changing more heavily (e.g. connection establishment, crash detection, signal handling, minor details of the locking code). But large portions of the code won't need to change. Note that we/postgres already shares a lot of state across processes.
I'm not the person you asked and I don't have any particular knowledge of postgres internals.
Experience with other systems has taught me that in a system that's been in active use and development for decades, entanglement will be deep, subtle, and pervasive. If this isn't true of postgres then it's an absolute freak anomaly of a codebase. It is that in other ways, so it's possible.
But the article mentions there being thousands of global variables. And Tom Lane himself says he considers it untenable for exactly this reason. That's a very good reason to think that it will require that many changes imo.
A large refactor at best. It will touch lots of parts of the code base, but the vast majority of the source code would remain intact. Otherwise they could just Rewrite it in Rust™ while they’re at it
> if every line needs to be audited and updated, it is a re-write
I’m not sure why you believe every line needs to be updated. Most code is thread agnostic.
The big problem there is that the people you are letting loose on the alternative, are lost from the original, so O loses steam that A gains. You still have to produce bug fixes and features to _both_ O and A to keep them in sync. So you essentially have a doubled required production rate to be delivered using the same staff.
So in order for there to be a net gain, the gang working on the alternative have to be able to find such big wins as to being neigh impossible.
This is a very very hard problem in our domain. 99% of the time, we have to simply resist the urge to _just rewrite the sucker_. No! Don't do it! (And this is incredibly hard because we all want to.)
Python3 changes were many "little" things; some more fundamental than other (unicode str). So I guess they were able to split the work in tiny pieces and, ultimately, were able to manage the project...
Yes, that was a rough migration process, but the long-term result is we have an improved language and growing community instead of Python going the way of PHP and Perl.
Between the 3 P's, Python's strategic decisions in 2000s were clearly the most successful.
I've used PHP in the past (PHP 4 and 5), as well as some simple templated projects in PHP 7. I try to keep up on news with what is happening in the PHP world, and it's difficult because of the hate for the language. Is the solution to Unicode strings still to just use the "mb_*" functions?
I got my real professional start using PHP, and have built even financial systems in the language (since ported to .NET 6 for my ease of maintenance, and better number handling). I'm still very interested in the language itself, in case I ever have the need to freelance or provide a solution to a client that can't afford what I can build in .NET (although to be honest, at this point I'm roughly able to code at the same speed in .NET as in PHP, but with the added type-safety, although I know PHP has really stepped up in providing this).
I believe so - most (all?) string functions have an mb_ equivalent, for working on multibyte strings.
Regular PHP strings are actually pretty great, since you can treat them like byte arrays. Fun fact: PHPs streaming API has an “in-memory” option and it’s… just a string under the hood.
Just don’t forget to use multibyte functions when you’re handling things like user input.
I have the "Professional PHP6" book which I feel like should be a collectors item or something.
Weird book IMO, because it has a lot of content that's just about general software development, rather than anything to do with PHP specifically, or the theoretical PHP6 APIs in particular.
PHP used to be the first computer language learned by people wanting to create a scripted web page. This was more true in the 90s but maybe it stuck. So it would be OK to add some general guidance about writing software and organizing projects.
For those who don't follow PHP closely - that version was an attempted refactor of the string implementation which essentially shut down nearly all work on PHP for a decade, stagnating the language until it became pretty terrible compared to other options. They finally gave up and started work on PHP 7 which uses the (perfectly good) PHP 5 strings.
Ten years of wasted time by the best internal PHP developers crippled the project - I'm amazed it survived at all.