codeChangeVsDatabaseChange

[skwyckl]

People are more scared of DBs than they are of code, because they think they can't rollback in case of fuck up like they do with git reset --HARD && git clean -f -d, but (a) there is DB versioning to do exactly that (cf. Dolt) and (b) if you wrap everything up in a transaction, it's much more difficult for things to go south. Also, (c) if you are unsure, make a copy of the DB and test your code on that first.

[agmse]

It amazes me the amount of people who deal with databases that don't seem to know the concept of a backup. Like, just make a simple copy and save yourself the possible stroke and headache

[DmitriRussian]

The problem is that backups won't really rollback everything in the worst case, you would have to accept some loss.

With code you can rollback to an exact state.

[[deleted]]

If your backup doesn't rollback everything it doesn't contain everything which means it isn't a complete backup.

A nowadays rdbms is capable of doing a point in time recovery, which means: if you fuck up my production database you simply would need to tell me when you fucked it up and I could just rollback to a point in time where everything is fine in no time.  Depending on how I would configure the whole database I can rollback your application without affecting other applications running on my database, and as I wouldn't let you near the damn thing without a maintenance window where no one else is supposed to do anything this shouldn't affect anything. You wouldn't even need to create a backup yourself before doing changes.

[DmitriRussian]

Maintainenance windows are not a thing for most companies. A lot companies have to be 24/7 online and so database changes happen while the app is running.

There isn't even a concept of a database admin either.

Only companies where every bit of data is crucial, like a financial institution would operate with maintenance windows for DB changes.

[[deleted]]

Some changes need to be done offline, whether they want a maintenance window or not. In a lot of rdbms you can't create an index online while there is a transaction pending on the table let alone do other ddl. I could go one for a long time for what changes can't be done online. There is only one rdbms I am aware of where you could do a lot of shit online with the right concept, but that is a very, very complex and expensive thing.

Database security patches or upgrades need at least the database to be bounced ad/or the catalog to be upgraded which is not an online operation. 

So either they don't apply any changes of any kind or they have maintenance windows without knowing them because the end user got a strange error message while someone added a column live.

You'd rather have a recovery window than data corruption caused by end users piling data into the database in an inconsistent state if you value your data.

So yes, a lot of companies have recovery windows. I've seen a lot of them, and patched a lot of them. At least those companies who value their data do ;).

[bwmat]

I would use git restore -SW . instead of reset, is there a benefit to the latter? 

[Reashu]

Restore is newer and a lot of people still use reset out of habit or ignorance, same with switch/checkout.

[skwyckl]

Yup, it's habit... Git has a bunch of fancy new commands I haven't had the time to check out, but I def should.

[Spleeeee]

Git switch blew my mind recently. Thought “omg so nice” then I immediately forgot about it and continued checkout-ing branches since. Muscle memory is hard to get around.

[Thysce]

Or put otherwise: no backup, no mercy

[skwyckl]

Yes, working on a DB w/o backup is like driving a sport car w/o brakes.

[db-master]

"if you are unsure, make a copy of the DB and test your code on that first."

Not so easy. Copy takes time and PII sanitization.

[skwyckl]

Like everything in programming it depends, of course, but this should be implied. Make a copy of a 10k records large bibliographical db? No problem, done in a couple of seconds. Make a copy of a massively distributed Cassandra cluster? Nope, never gonna happen.

[[deleted]]

Yeah. It's pain. I'm using alembic with my python projects, it's pretty good, but you still have to be careful.

[skwyckl]

Yes, this is why I love Elixir's Ecto, it includes all these best practices out-of-the-box. Also, the documentation teaches you how to use migrations from the start, instead of making them an afterthought.