171–180 of 416 posts
How is Cassandra as an alternative to MongoDB?
Earlier quoted context omitted.
DynamoDB conditional writes are strongly consistent. Defaulting to inconsistent reads was reckless and I would never defend that, but the worst case is non-repeatable stale results, never lost writes.
It’s clearly documented everywhere that reads are eventually consistent by default.
"We found that due to these weak defaults, MongoDB’s causal sessions did not preserve causal consistency by default: users needed to specify both write and read concern majority (or higher) to actually get causal consistency. MongoDB closed the issue, saying it was working as designed, and updated their isolation documentation to note that even though MongoDB offers “causal consistency in client sessions”, that guara…
Kyle's point is that it's arguably valid but certainly unhelpful: the default settings are liable to lead to data loss. Moreover, he draws attention specifically to transactions as something which you would expect to make things safer, but in fact there's a rather arcane part of the documentation that notes that you need to manually specify both read and write concerns on every transaction individually if you want tr…
In Mongo's defense, the defaults are similar to what you would likely have with a replicated MySQL/Postgres cluster (single node accepting writes with slaves replicating from there; no concept of write concern). My assumption here is that he is assuming the primary dies before the writes have replicated to the secondaries; that is exactly how master-slave fails too. Maybe there are systems folks can use for having write concern in those databases, but in the companies I've worked for we didn't have them and we definitely didn't have automated failovers
Earlier quoted context omitted.
mysql's admin tools are still far superior than what's available for postgres
What tools are these? Curious as a Postgres user
For MySQL, I haven't found anything that beats SequelPro. For Postgres, I haven't found anything that comes close to parity, but my favorite is Postico.
I know people that swear by IntelliJ for their db stuff, it just never hit home for me personally though.
Earlier quoted context omitted.
MySQL does not scale better than PostgreSQL. I can tell you this emphatically as I spent 6 months trying to eke out performance with MySQL (5.6). PostgreSQL (9.4) handled the load much better without me having to change memory allocators or do any kind of aggressive tuning to the OS. MySQL has some kind of mutex lock that stalls all threads, it's not noticeable until you have 48cores, 32 databases and a completely un…
MySQL 5.6 was released in 2012. Postgres 9.5 was released in 2016, so this isn't really a fair comparison.
yes, I should run the test again, but it was 6 months of my life, and I don't see how much could have changed.
Earlier quoted context omitted.
MySQL does not scale better than PostgreSQL. I can tell you this emphatically as I spent 6 months trying to eke out performance with MySQL (5.6). PostgreSQL (9.4) handled the load much better without me having to change memory allocators or do any kind of aggressive tuning to the OS. MySQL has some kind of mutex lock that stalls all threads, it's not noticeable until you have 48cores, 32 databases and a completely un…
You comparing tech from 2 different eras... redo the benchmark today and I’ll be surprised if you come to the same results. PGsql even has a wiki page where they discuss implementing MySQL features and changing their architecture so they can scale. https://wiki.postgresql.org/wiki/Future_of_storage#MySQL.2FM...
They were both the latest and greatest at the time
> redo the benchmark today and I’ll be surprised if you come to the same results.
I would, but it was not just a benchmark, it was a deep undertaking including but not limited to: optimisations made in the linux kernel, specialised hardware along with custom memory allocators and analysing/tracing/flamegraphing disk/memory access patterns to find hot paths/locks/contention. (and at different scales: varying the number of connections, transactions per connection, number of databases, size of data, etc)
It was 6 months of my life.
> PGsql even has a wiki page where they discuss implementing MySQL features and changing their architecture so they can scale.
Just because mysql has some good ideas doesn't mean it scales better. I know for a fact that it didn't in 2015. I doubt that they have fixed the things I found, I could be wrong. But it would have to be a large leap forward for MySQL and PostgreSQL has had large performance improvements since then too.
also, I read that page and it talks nothing about scaling, just that some storage drivers have desirable features (memory tables are very fast, and PGSQL doesn't support it; archive tables are useful for writing to slower media, you can do this with partitioning but it's not intuitive)
In the circles I run in, MongoDB is regarded as a joke and the company behind it as basically duplicitous. For example, they still list Facebook as their first user of MongoDB on their website, for example, but there is no MongoDB use in Facebook hasn't been for years (it came in only via a startup acquisition). I had the misfortune to use MongoDB at a previous job. The replication protocol wasn't atomic. You would f…
I was floored by this comment yesterday from one of their Developer Relations people: > Did any of you actually read the article? We are passing the Jepsen test suite and it was back in 2017 already. So, no, MongoDB is not losing anything if you know what you are doing. https://twitter.com/MBeugnet/status/1253622755049734150?s=20 Can you imagine saying the phrase "if you know what you are doing," in public, to your u…
However I can _quite easily_ see how a non-native English speaker could use the phrase “if you know what you are doing” to mean “if you are careful”.
Earlier quoted context omitted.
SQLite: I enjoy using reliable and correct databases even at the cost of scalability
SQLite has always intentionally failed to report this error: sqlite> create table foo (n int); sqlite> insert into foo (n) values ('dave'); sqlite> select count(*) from foo where n = 'dave'; 1
SQLite does not use column typing except in integer primary keys.
Edit: never mind, I think the other URL - http://jepsen.io/analyses/mongodb-4.2.6 - deserves a more technical thread, so will invite aphyr to repost it instead. It had a thread already (https://news.ycombinator.com/item?id=23191439) but despite getting a lot of upvotes, failed to make the front page (http://hnrankings.info/23191439/). I have no idea why—there were no moderation or other penalties on it. Sometimes HN's software produces weird effects as the firehose of content tries to make it through the tiny aperture of the frontpage.
Earlier quoted context omitted.
SQLite: I enjoy using reliable and correct databases even at the cost of scalability
I admit I was kind of thinking that, even though I appreciated the humor. :) I imagine an awful lot of web sites out there would do just fine with SQLite as their back end.