I’ve found people often overlook that while code can be very quickly deleted, gigabytes or terabytes of production data is a huge pain to ETL later. Investing in the data model upfront has huge payoffs for your code and avoiding ETLs later on.

When can you rebuild at zero cost?

I have made similar avoidable mistakes of not thinking it through enough, could have saved me a lot of rewriting, which was pretty expensive

Rewriting is incredibly cheap! And you learn a lot from the failed attempts.

Again to the house analogy, if you could just build 3 vestibules to see how they fit with just a little typing, that would be far and away preferable to committing to everything on paper before hand.

No, it is not cheap, generally.

Example:

Dendrite[0] was going to be a Rewrite of Synapse (which was a prototype which ended up going into production). The rewrite started more than 5 years ago, had lots of development breaks and it still is nowhere complete or close to replace a existing Synapse instance (which even today is ... Well ... suboptimal software).

The current plans are to support and use both servers long term, because Synapse is already too widespread.

I wouldn't call that cheap.

[0]: https://github.com/matrix-org/dendrite

Well starting from scratch for a rewrite is generally a bad idea. I'm more a fan of incremental re-wrties. But I have code bases I have been working on for years with tens of thousands of lines where basically the entire thing gets rewritten ever 18 months or so, a bit at a time.

Isn't your example proof of the benefit of pragmatic coding? Synapse is actually serving users right now. Dendrite sounds like a "better design" which is stuck in purgatory.

They tried an incremental rewrite before. They failed, and started Dendrite.

https://matrix.org/blog/2020/10/08/dendrite-is-entering-beta

Survivor bias.

You don't see all the perfectly designed codebases that never went anywhere.

We only talk about legacy code because it's the one that pays the bills.

Are you the only working on the codebase? It may be easy to rewrite your own codebase, but it's certainly not easy to rewrite someone else's. Especially if they haven't been caring about code quality and/or test coverage.

My definition of "good-quality" code is pretty much exactly "how difficult would this codebase be for a new engineer to understand and modify safely."

You can go really really fast when you don’t give a shit about consequences.

Often the worst code comes from prolific people. There’s just so much if it. And if you touch it you will break it at least 1% of the time, so you have to pick your battles when you are trying to keep the ratio under control.

If you write loosely-coupled code, it shouldn't be that easy to break things unless you're careless.

Nobody in this whole post is talking about loosely coupled code. If you find someone complaining about how hard it is to modify loosely coupled code, you have my permission to fire them.

For everyone else this is tautological. Good code can continue to be good code.

If it were loosely coupled it wouldn’t be an anecdote in this conversation. There is no “I”, there is no “you”. There is only “us”. I can only control Us so much, and I don’t have a time machine.

People who only have green field projects as their context are very frustrating in conversations like this. They make suggestions like, well, don’t fuck up in the first place. I don’t know what your history is but that’s the feeling I’m getting.

Not that it matters but I've worked on a mix of green-field projects and mature codebases in various domains with teams of various sizes over more than a decade of professional experience.

I could assume you're throwing shade on "prolific programmers" out of some sense of insecurity, but it wouldn't be fair to generalize about strangers on the internet ;)

No, It’s an overdeveloped sense of justice.

I just punch up at condescending people. Every discipline has a bunch of armchair people who don’t understand the problem who think “get more exercise” is the response to depressed people or people with chronic fatigue, “eat fewer calories” is the answer to weight issues or diabetes, or “write it right the first time” is a useful response to people trying to solve real world problems.

Kindly let the grownups talk and keep your flash card answers to yourself.

> Kindly let the grownups talk

Well one of us is certainly being condescending ;)

And did you really answer twice to the same comment? My goodness I must have really struck a nerve.

Well this escalated quickly

If everyone is discussing a problem that you don’t see, then why offer your simple solution except to appear smart? And who needs to appear smart? That’s your insecurity. Not mine.

Idk maybe it's because I did freelancing for quite some time and was often hired to clean up somebody's mess, but I think it's not so bad to rewrite someone else's code. What I normally do is quarantine the old code behind a clean interface, or else start fresh with a better code structure, and then copy and paste the good bits of business logic from the old project into the new one.

Code has a lot of really great properties which make it easy to modify in provably safe ways if you know what you're doing.

That really depends on what you're working on and to what degree it's coupled to the system it's a part of. A form on a web application, or an API endpoint? Sure, rewriting it is probably trivial. A new process scheduler for Linux? The caching system in an HTTP server? Maybe writing the code will be easy (though probably not), but building any confidence that it doesn't break something that's unexpectedly load bearing will be anything but cheap. And if what you're rewriting that started out as "just code and see what happens" it's going to be more expensive still.

Which isn't to say that rewriting can't be cheap, but some intentional design (or at least diligent maintenance and refactoring) must have gone into the system to support that style of development. At which point you're back to targeting "quality," even if it's no longer a focus of on the smaller scale.

How are defining cheep, and how big is the metaphorical house? Developer time is not free (unless you are working a personal project) and if an hour or two up front of planning things out stops you from making a lynch pin mistake that needs to be re-written it is better to do the planning.

If the amount of time that it takes to rewrite something is trivial (a week or less) then you aren't working on something all that big/complicated.

Probably not literally without cost, but if the code was written with disposability in mind combined with just a little bit of pre-planning, then rewriting or refactoring should be indeed trivial.

When start off with "wrong" higher level design concepts, neither of those is trivial.

If you're writing a function implementation without thinking about design, well you might be right.

I sometimes wonder if there is a miscommunication. I’m scratching my head sometimes like “how can rewriting/refactoring an entire 10-20k project take negligible time?”

Maybe some people have very small projects compared to what I work on? Or maybe they are talking about the design of a single small component?

I inherited a codebase that needed some refactoring because it was written “to just get it shipped”. If completely fell apart with more users and has taken me a year to get it where it needs to be.

But how often would you actually have to rewrite an entire 10-20k LOC project at once?

As you need to add functionality, you can opportunistically find ways to improve the codebase toward a better/more maintainable structure.

I have several large codebases I work on which probably get totally rewritten every 18 months or 2 years, however incrementally.

If you have a working project and you think you need to throw it all out and start from scratch probably it's worth a second thought.

We always talk about time when the elephant in the room is energy. People say we don’t have “time” for that and someone else gets out a calendar and tries to disprove them. Followed by a bunch of backpedaling with other excuses and followed up with foot dragging.

The second elephant in the room is job security. People who write baroque code are hard to fire. Nobody wants to invest energy in understanding their private little Bedlam.

When starting, yes it's easy to replace code, even with a shitty design. If it had to take more than ten hundred thousands lines of code to realize that the design is wrong, then it means the author lacks enough awareness or foresight to plan ahead, and no amount of planning will fix that. Code should be replaced/rewritten if the earliest signs faulty design show up, which should be trivial if the code was and remains "disposable".

Not having to pay for physical materials doesn’t mean there are no costs. Throwing hours, days, or weeks of focused work time out the window does not sound cost free to me or Whoever signs paychecks.

It's not throwing it out the window if it's an iteration toward a better solution. There's a reason nobody does waterfall anymore in software - up-front planning is less productive than rapid prototyping in most cases.

The development of the relational model of databases is an example where thinking things through led to a radically different and superior solution, going in a very different direction than ad-hoc development had produced, or was ever likely to produce. At the time Codd published his seminal paper, there were no implementations of those ideas.

It is also notoriously difficult to get the design of concurrency primitives correct without thinking things through.

Yeah, but >99% code is about using relational DBs and concurrency primitives not developing them. There are somethings that would depend on solid theoretical understanding but most of the software today is much more amenable to trying out things first and reworking failed parts.

In practice, one does not write a single line of code without feeling that it is somehow getting you closer to the desired outcome. If you have the ability to anticipate that it will not contribute to that goal, or that it will create problems on the way, or that there is a better way, even before you have written and tested it, then it would be counterproductive not to do so.

But there's also such a thing as over-planning. If every function you write, you are thinking about 100 different rules about "best practices" you can end up not writing anything at all. Sometimes it's better to accept some level of imperfection first and refine later.

Sure, but your reply to Jcbrand was dismissive of the idea that there is any value to thinking ahead. Jcbrand was not advocating 'thinking about 100 different rules about "best practices"', only that it is useful to try to work out the consequences of the choices you make, in advance of those consequences being revealed to you by failed tests (or failures in use.)

I have no idea why there is a large (or at least vocal) community of developers whose dogma seems to be that thinking things through is a waste of time (though maybe it is just an overreaction to the equally dogmatic clean coders and similar prescriptivists.)

I mean it's always a bit of a middle ground isn't it? I'm not suggesting that you should literally just sit down at a keyboard and blindly start typing - of course you want to have at least some concept of how you want to approach the problem.

My point is more that coding itself is an excellent tool for probing for solutions. In many cases I think "software design" is over valued, and time spent prototyping is often more valuable than time spent thinking though the problem if you want to arrive at a high quality answer.

As someone who is currently over a year into rewriting a massive system with a fundamental design error by the original designer I can assure you that failing to plan your data model up front can have huge costs not just for you but for anyone who picks up your code in the future, and can hamstring a system so that it is impossible to extend or evolve.

What was the design error?

It's a platform for managing a kind of appointment, but it doesn't have an appointments table. The appointments data is combined with a different table, and there was no way to disentangle them easily because the entire system was built around that object model. Case study in failure to normalize.

The hard part is done, but basically we had to switch the engine while the car was running so to speak. In order to switch this out you need to start writing the correct data shape, then switch everything over to reading that shape. When people work strict 9 to 5s this will take you forever especially when managing a large amount of volume, which requires you to be extremely risk-averse and slow.

I don't know about your experience but refactoring is just not on the menu in most commercial environments I'm familiar with, therefore if you always pick the first solution that cones to find, it is likely you have to leave with the consequences of the hack for a long time (until the system crumbles under its own complexity).

I guess I have been lucky - I've always been able to negotiate for time to refactor if needed, or just find time for it in lulls between tasks. If you're in an environment where engineers don't have the freedom to improve their codebase I would not consider that to be a healthy practice, but that certainly would change the value proposition around upfront design.

I refactor all the time and have done it for 25+ years. The result is solid code that is easy to maintain and close to bug free (no bugs in production the last 5+ years).

Could you describe the process: did you need to justify the time spent on refactoring in any way? ("why known bugs, requested new features should wait until the refactoring is done"--I'm playing devils advocate here. I'm interested, how you justified it before the management if you had one)

I never asked permission to do it. I consider refactoring to be part of my job. Small refactorings I do right away when implementing a new feature. Large ones I split into many small steps and work on for months in-between working on new features. Never underestimate the power of making a small improvement every day. I make sure that the long term refactorings never breaks the system or introduce new bugs. I have solid tests in place making sure changes doesn’t change behaviour.

This is a very self-centered way to think about things. I don’t mean selfish, I mean thinking as a “me” problem instead of an “us” problem.

If I have to rewrite a bit of my code then them’s the breaks. But I work on a team, sometimes a big team. I don’t have “a house” I have a construction crew that is building many houses and will go on building them. If they’re doing it wrong then I have not only the problem in front of me but five copies elsewhere. And I can’t fix problems N times faster than they are made. And I can’t always sell them on the better technique, even when there are demonstrable problems with theirs.

I want to work with people who I trust to rewrite my code.

And of course I don't mean that you should check in code which is a mess. But from the time you start a feature to the time you open a PR, you can go through several iterations of messy code before arriving at a solution which is fit to share with your colleagues.

I do too, but I can’t spend my whole life interviewing, and sometimes great teams just run out of money.

Usually you can't delete half your codebase and re-build it at zero cost. The cost of developing a codebase is often the primary cost for software companies.

The cost of the knowledge of that code and the techniques that created is spread in five to fifty other brains. That’s the hard part. You keep finding new copies of patterns you’re trying to remove.

In a couple of notable cases, that didn’t stop until I removed the last copy. My theory is that certain people were cutting and pasting code from one of the three surviving copies.

> "If you could delete half your house and re-build it at zero cost, it might..."

I look forward to that day when atoms are commanded like bits!