Submitted 1 year ago by drekly@lemmy.world to programming@programming.dev
“UPDATE table_name SET w = $1, x = $2, y = $4 WHERE z = $3 RETURNING *”,
does not do the same as
“UPDATE table_name SET w= $1, x= $2, y = $3, z = $4 RETURNING *”,
It’s 2 am and my mind blanked out the WHERE, and just wanted the numbers in order of 1234.
FML.
This doesn’t help you but may help others. I always run my updates and deletes as selects first, validate the results are what I want including their number and then change the select to delete, update, whatever
I learned this one very early on in my career as a physical security engineer working with access control databases. You only do it to one customer ever. 🤷♂️
That’s an easy one to recover from:
Simply fake your own death and become a goat herder in Guatemala.
I still remember that time (hours ago) when “fake your own death” was the top voted recommendation for recovering from a SQL mistake.
Sign me up!
Pro tip: transactions are your friend
Completely agree, transactions are amazing for this kind of thing. In a previous team we also had a policy of always pairing if you need to do any db surgery in prod so you have a second pair of eyes + rubber duck to explain what you’re doing.
They are - until you leave them open and go home…
Temporarily locked overnight >>> broken stuff in prod
This is the way.
PG has a useful extension, pg_safeupdate
github.com/eradman/pg-safeupdate
It helps reduce these possibilities by requiring a where clause for updates or deletes.
I guess if you get into a habit of adding where 1=1 to the end of your SQL, it kind of defeats the purpose.
MySQL (and by extension, MariaDB) has an even better option:
mysql --i-am-a-dummy
Amazing! These are going in my.conf ASAP.
Transactions help more, IMO. The 1=1 becomes a real habit.
Databases have special configuration that warn or throw error when you try to UPDATE or DELETE without WHERE. Use it.
I tried to find this setting for postgres and Ms SQLserver, the two databases I interact with. I wasn’t able to find any settings to that effect, do you happen to know them?
It’s supported in MySQL and MariaDB out of box:
dev.mysql.com/doc/…/mysql-command-options.html#op…
In Postgres there is an extension for it:
for postgres and Ms SQLserver
It’s not really a SQL Language feature, more an IDE feature. So to tell you where the settings are, we’d have to know which IDE you’re using.
For example, in DataGrip (which I think you can use both for postgres and MSSQL), there’s “Show warning before running potentially unsafe queries”
If you forgot to put the WHERE clause in DELETE and UPDATE statements, DataGrip displays a notification to remind you about that. If you omitted the WHERE clause intentionally, you can execute current statements as you planned.
You’re not the first. You won’t be the last. I’m just glad my DB of choice uses transactions by default, so I can see “rows updated: 3,258,123” and back the fuck out of it.
I genuinely believe that UPDATE and DELETE without a WHERE clause should be considered a syntax error. If you want to do all rows for some reason, it should have been something like UPDATE table SET field=value ALL.
Because I’m relatively new at this type of thing, how does that appear on the front end? I’m using a js/html front end and a jsnode backend. Would I just see a popup before I make any changes?
If you’re asking about the information about the number of rows, oracle db clients do that. For nodejs, oracle’s library will provide this number in the response to a dml statement execution. So you can retrieve it in your backend code. You have to write additional code to bring this message to the front-end.
No idea. My tools connect directly to the DB server, rather than going though any web server shenanigans.
this folks, is why you don’t raw dog sql likes some cavemean
Me only know caveman. Not have big brain only smooth brain
Yep. If you’re in a situation where you have to write SQL on the fly in prod, you have already failed.
it’s time to commit sqlpukku
Raw dog is the fastest way to finish a task.
It’s a trade-off
There’s no way you’re endorsing the way OP handled their data right?
Always SELECT first. No exceptions.
Better yet… Always use a transaction and have backups.
mind explaining?
By running a select query first, you get a nice list of the rows you are going to change. If the list is the entire set, you’ll likely notice.
If it looks good, you run the update query using the same where clause.
But that’s for manual changes. OP’s update statement looks like it might be generated from code, in which case this wouldn’t have helped.
I did when I made the query a year ago. Dumdum sleep deprived brain thought it would look more organised this way
I once dropped a table in a production database.
I never should have had write permissions on that database. You can bet they changed that when clinicians had to redo four days of work because the hosting company or whatever only had weekly backups, not daily.
So, I feel your pain.
You all run queries against production from your local? Insanity.
Everyone has a production system. Some may even have a separate testing environment!
The lines get blurry if you’re the sole user.
My only education is a super helpful guy from Reddit who taught me the basics of setting up a back end and postgres. After that it’s just been me, the references and stack overflow.
I have NO education about actual practises and protocol. This was just a tool I made to make my work easier and faster, which I check in and update every few months to make it better.
(but of course this has set me back so much it would have been quicker not to make the tool at all)
If coffee simply does not get you out of bed in the mornings any more, you need to find your fix elsewhere 💁
There is still the journal you could use to recover the old state of your database. I assume you commited after your update query, thus you would need to copy first the journal, remove the updates from it, and reconstruct the db from the altered journal.
This might be harder than what I’m saying and heavily depends on which db you used, but if it was a transactional one it has to have a journal (not sure about nosql ones).
It is after the event that I find that postgres’ WAL journalling is off by default 🙃
Periodic, versioned backups are the ultimate defense against bugs.
Periodic, versioned and tested backups.
It absolutely, totally, never ever happened to me that I had a bunch of backups available that turned out to be effectively unrestorable the moment I needed them. 😭
The worse feeling than realizing you don’t have backup is realizing your backup archives are useless.
WHO, WHAT, WHERE, WHEN, WHY, HOW
who thought it was a good idea to make the where condition only correct syntax after the set?? disaster waiting to happen
The people designing SQL, not having learned from the mistakes of COBOL, thought that having the syntax as close to English as possible will make it more readable.
There was a time I worked as a third party for one of the 10 most accessed websites in my country. I got assigned to a project that has been maintained by another third party for 10+ years with no oversight. I have many stories from there but today’s is that this company had very strict access control to the production database.
Third parties couldn’t access the database directly. All fine and good, except for the fact that we were expected to setup some stuff in the database pretty much every week. The dude who kept this project running for the previous decade, unable to get proper credentials to do his job, instead created an input box in some system that allowed him to run any sql code.
You can already guess the rest of the story, right? For security reasons we had to do things in the least secure way imaginable. Eventually, wheres were forgotten.
But if they had such strict access control they also had backups. Right? Right?!
They did.
I watched someone make this mistake during a screen share, she hit execute and I screamed “wait! You forgot the where!” Fortunately, it was such a huge database that SQL spun for a moment I guess deciding how it was going to do it before actually doing it, she was able to cancel it and ran a couple checks to confirm it hadn’t actually changed anything yet. I don’t think anything computer related has ever gotten my adrenaline going like that before or since
I did that once when I moved from one DB IDE to another and didn’t realise the new one only ran the highlighted part of the query.
there were thousands of medical students going through a long process to find placements with doctors and we had a database and custom state machine to move them through the stages of application and approval.
a bug meant a student had been moved to the wrong state. so I used a snippet of SQL to reset that one student, and as a nervous habit highlighted parts of the query as I reread them to be sure it was correct.
then hit run with the first half highlighted, without the where clause, so everyone in the entire database got moved to the wrong fucking state.
we had 24 hourly backups but I did it late in the evening, and because it was a couple of days before the hard deadline for the students to get their placements done hundreds of students had been updating information that day.
I spent until 4am the next day working out ways to imply what state everyone was in by which other fields had been updated to what, and incidentally found the original bug in the process 😒
anyway, I hope you feel better soon buddy. it sucks but it happens, and not just to you. good luck.
In MSSQL, you can do a BEGIN TRAN before your UPDATE statement.
Then if the number of affected rows is not about what you’d expect, doing a ROLLBACK would undo the changes.
If the number of affected rows did look about right, doing a COMMIT would make the changes permanent.
Yup, exact tip I was gonna write!
I have them commented out and highlight the COMMIT when I’m ready.
I have done this too. Shit happens.
One of my co-workers used to write UPDATE statements backwards limit then where etc, to prevent this stuff, feels like a bit of a faff to me.
Thanks for sharing your painfull lesson. I don’t interact with DB’ directly a lot, but WHEN I do in the future I’ll select first and validate… Such things can happen sk fast. No self hate, man!
Unrelated, but use placeholders instead of interpolation right into the query.
See: Little Bobby Tables. xkcd.com/327/
That’s what they’re doing…
If true, great. I’ve not run across a language / RDBMs library that uses numbered place holders over the standard ?, but I’m sure someone’s done it.
Depending on the database used, the data might still be there, just really hard to recover (as in, its presence is a side-effect, not the intent).
stackoverflow.com/a/12472582 takes a look at Postgres case, for example.
you could use dbeaver that warns you for update and delete queries without a where clause, independently of the db system. I hope the functionality it’s still there since, for totally unrelated motivations, I always use a where clause, even when buying groceries.
I learned the hard way about the beauty of backups and the 3, 2, 1 rule. And snapshots are the GOAT.
Even large and (supposedly) sophisticated teams can make this mistake, so dont feel bad. It’s all part of learning and growth. You have learned the lesson in a very real and visceral way - it will stick with you forever.
Example - a very large customer running our product across multiple servers, talking back to a large central (and shared) DB server. DB server shat itself. They called us up to see if we had any logs that could be used to reconstruct our part of their database server, because it turned out they had no backups. Had to say no.
This is about the one thing where SQL is a badly designed language, and you should use a frontend that forces you to write your queries in the order (table, filter, columns) for consistency.
UPDATE table_name WHERE y = $3 SET w = $1, x = $2, z = $4 RETURNING * FROM table_name SELECT w, x, y, z
I get mildly mad all the time when writing SQL because I feel like it’s upside down
Instead of
select u.id. u.email, p.name from user u join persona p on p.user_id = u.id where u.active = true
where the columns are referenced before they’re defined (like what is u.id? Keep reading to find out!)
it should instead be
from user u join persona p on u.id = p.user_id where u.active = true select u.id, u.email, p.name
Now nothing is defined before it’s used, and you’re less likely to miss your where clause. I usually write the joins first anyway because I know what tables I care about, but don’t know which specific things I’ll want.
I can’t think of any other languages that use things before they’re defined except extremely dysfunctional JavaScript.
You might enjoy github.com/max-sixty/prql
From the cabinet, get a cup.
A gut wrenching mistake, hopefully you’ll only make it once!
Oof. Been there, done that, 0 stars; would not recommend.
I don’t know if it makes you feel better but Tom Scott had a similar experience: youtu.be/X6NJkWbM1xk
Pressing F to pay respects. R.I.P. in pieces
Depending on how mission critical your data is…Set up delayed replicas and backups (and test that your backups can actually be restored from). Get a second pair of eyeballs on your query. Set up test environments and run it there before running it in production. The more automated testing you put into your pipeline, the better. Every edit should be committed and tested. (Kubernetes and GitLab Auto DevOps makes this kind of thing a cinch, every branch has a new test environment set up automatically)
Don’t beat yourself up too much though. It happens even to seasoned pros.
AlphaOmega@lemmy.world 1 year ago
This is a good lesson to learn the hard way. From now on, my guess is you will have dozens of backups.
marcos@lemmy.world 1 year ago
And a development environment. And not touch production without running the exact code at least once and being well slept.
ReluctantMuskrat@lemmy.world 1 year ago
And always use a transaction so you’re required to commit to make it permanent. See an unexpected result? Rollback.
sim642@lemm.ee 1 year ago
Transactions aren’t backups. You can just as easily commit before fully realizing it. Backups, backups, backups.
Tylerdurdon@lemmy.world 1 year ago
This is the way