AlisdairO

7 ms·

1.
by AlisdairO 7mo ago
Only on a per-connection basis
2.
by AlisdairO 8mo ago
It supports transactional schema changes, but that's not what I'm talking about. Most schema changes require heavyweight locks on the tables they're altering. The locks might be short lived (for example, just a catalogue upda
3.
by AlisdairO 8mo ago
Regarding schema changes and timeouts - while having timeouts in place is good advice, you can go further. While running the schema rollout, run a script alongside it that kills any workload conflicting with the aggressive locks the schema
4.
by AlisdairO 1y ago
Depending on exactly what you need, you can often fake this with a functional index on mod(queue_value_id, 5000). You then query for mod(queue_value_id,5000) between m and n. You can then dynamically adjust the gap between m and n based on
5.
by AlisdairO 2y ago
Me> different people will have different strengths of addiction You> It's profoundly obvious you're missing the point, and conflating somehow having a low degree of addiction to something with not being addicted at all to it
6.
by AlisdairO 2y ago
> How have fat people gotten thinner without those meds up until now, then? Mostly, they haven't. You and I are outliers. The population-level data tells us that overweight people are mostly unable to control their weight in the fac
7.
by AlisdairO 2y ago
Respectfully, have you ever had anything in your life that you have struggled desperately with, and needed help? Anything at all that might give you a little empathy on the topic? I was obese twenty years ago, and lost the weight via diet a
8.
by AlisdairO 2y ago
I used to (and I didn't find much relief from eye drops). For the headaches, turned out they were migraines, which I was getting from screwing up my face because my eyes were uncomfortable.
9.
by AlisdairO 2y ago
* In that link, V11 is not the version of Postgres, it's the version of the test. Scroll down to DB Version. * Lots of versions are tested, but 9.2.1 is the only version I see on the same hardware that the top MariaDB versions
10.
by AlisdairO 2y ago
That link isn't particularly convincing. As far as I can see, the only Postgres test performed on the hardware that the top MariaDB entries had was on a positively ancient Postgres version (9.2.1).
11.
by AlisdairO 2y ago
self-plug, but you could give https://pgexercises.com/ a try. No need to spin up your own DB etc.
12.
by AlisdairO 3y ago
Why shouldn't they want the easy way out? I was obese twenty years ago, and lost the weight via diet and exercise. Keeping that weight off is the single hardest thing I have ever done, and a battle I still have to consciously fight e
13.
by AlisdairO 3y ago
Indeed - People In The Know have some cocnerns with this approach: https://ardentperf.com/2021/07/26/postgresql-logical-replica... . At $work we did use this approach to upgrade a large, high throughput PG da
14.
by AlisdairO 3y ago
Do that in most relational dbs in the default isolation level (read committed), and concurrently executing transactions will still be able to delete users underneath you after the select. If we take postgres as an example, performing the se
15.
by AlisdairO 3y ago
I think it because a significant fraction of my career has been spent fixing db-concurrency-related mistakes for people once they hit scale :-). I’m not talking about using cascade - this applies perfectly well to use of on delete restrict.
16.
by AlisdairO 3y ago
Can you give an example? I’m not aware of a mechanism like that that will protect you from concurrency artifacts reliably - certainly not a general one.
17.
by AlisdairO 3y ago
> so long as your code is correct This is a pretty tough definition of correct, though. Without foreign key constraints you'll have a really tough time dealing with concurrency artifacts without raising your isolation levels, which
18.
by AlisdairO 3y ago
Table User: userid, etc Table Resources: resourceid, userid, etc If I want to restrict deletion of a user to only be possible after all the resources are deleted, I'm forced into using higher-than-default isolation levels in most DBs.
19.
by AlisdairO 3y ago
How does this stay correct in the presence of concurrent activity?
20.
by AlisdairO 4y ago
HA on rds uses synchronous replication - you won’t lose data on automated failover under any normal circumstances.
21.
by AlisdairO 4y ago
This is the c-store paper, which was evolved into Vertica: http://www.cs.umd.edu/~abadi/vldb.pdf . It's very readable, worth a look. edit: column stores existed before c-store, but c-store did some very nifty stuf
22.
by AlisdairO 4y ago
Fair enough - I've seen it more commonly in smaller machines, but they're also more common in the fleets I've observed (and the ones that are more likely to run close to the edge memory-wise). I have also seen it in systems u
23.
by AlisdairO 4y ago
I think the key here is what you mean by using swap. Having a lot of data swapped out is not bad in and of itself - if the machine genuinely isn't using those pages much, then now you have more space available for everything else. What
24.
by AlisdairO 4y ago
> If you have a build farm / CI machines, don't use swap. With swap, if a user schedules too many compiles at once, machine will slow to a halt and become kinda-dead, not quite tripping dead timer, but not making any progress e
25.
by AlisdairO 5y ago
just a note that in newer versions of PG I believe partition changes no longer require an access exclusive lock on the parent table, which I'm looking forward to when we upgrade...
26.
by AlisdairO 5y ago
As they note table lock acquisition can be super painful. It's possible to write a script to use pg_stat_activity to detect that the table alteration is waiting on a lock and kill conflicting work. For some workloads the kill is unacce
27.
by AlisdairO 5y ago
Particularly in the dynamo case, you're working outside of a common buffer pool. One of the key benefits of normalization in a typical db is that you can fit more stuff into memory if you normalize - dynamo renders that point largely m
28.
by AlisdairO 5y ago
To confirm, RDS does support in place major version upgrade for postgres.
29.
by AlisdairO 5y ago
The query hint thing is a serious issue. I get the concern that people won't report issues and so on, but on heavily loaded DBs having no decent operational response to a bad plan change is really scary. In an ideal world something lik
30.
by AlisdairO 5y ago
> That's a language design issue. Agreed. And, also, who cares? Yes, Java is a mediocre language and way too verbose. I spend a bunch of time in Java and I don't notice the worst of that because I (like literally every Java dev

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