3 ms·

Sounds like "yes, with an if" where the "if" is "if you don't really care about data consistency". "Last write wins" sounds like a recipe for disaster IMO. Th

Sounds like "yes, with an if" where the "if" is "if you don't really care about data consistency". "Last write wins" sounds like a recipe for disaster IMO. This is still one of those things that keeps people on MySQL - there are not one, but two open-source solutions available that provide synchronous cluster replication, allowing for "safe" writes against multiple primaries.

nyrikki 1y ago
It's all tradeoffs, with MySQL multi-master and multi-source models having their own issues and pg also has other options with their own tradoffs. ACID+distributed== tradoffs that will always keep this a horses for courses problem.
wfn 1y ago
Out of curiosity, what conflict resolution options exist in mysql and/or mysql cluster (never checked / exp. in PG)? Because you'll always have to address conflicts of course - we come to CAP / PACELC. Hm [1][2] - looks like they support more strategies (possibly) but I mean none of them are somehow magical, and timestamp comparison based methods comprise the better part of offered strategy set (looks like?) - and "latest timestamp wins" at least used to be the default (did not read thoroughly mind you, was just curious)? But I could be totally wrong - (1) curious if someone could link to things / explain, and (2) fyi ('stephenr) last write wins based on timestamp is a thing im mysql world as well (though again maybe set of options / different conflict resolution methods available is larger in mysql?) [1]: https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-replication-conflict-resolution.html https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-replic... [2]: https://dev.mysql.com/blog-archive/enhanced-conflict-resolution-with-mysql-cluster-active-active-replication/ https://dev.mysql.com/blog-archive/enhanced-conflict-resolut... (nice writeup, maybe outdated idk?)
- stephenr 1y ago
  For reference those two pages are both about NDB cluster. The two "options" I was referring to are MySQL group replication and the Galera replication plugin for MySQL. Both provide synchronous replication, so the write either succeeds to a majority of the cluster or is rejected.
  - wfn 1y ago
    Understood, thanks! I wasn't even sure where to look - thank you
agnivade 1y ago
Just for my own understanding, could you clarify why you think "last write wins" is a recipe for disaster?
- stephenr 1y ago
  Because two simultaneous writes mean some change is just lost, without feedback to the writer.

nyrikki 1y ago

It's all tradeoffs, with MySQL multi-master and multi-source models having their own issues and pg also has other options with their own tradoffs. ACID+distributed== tradoffs that will always keep this a horses for courses problem.

wfn 1y ago

Out of curiosity, what conflict resolution options exist in mysql and/or mysql cluster (never checked / exp. in PG)? Because you'll always have to address conflicts of course - we come to CAP / PACELC. Hm [1][2] - looks like they support more strategies (possibly) but I mean none of them are somehow magical, and timestamp comparison based methods comprise the better part of offered strategy set (looks like?) - and "latest timestamp wins" at least used to be the default (did not read thoroughly mind you, was just curious)? But I could be totally wrong - (1) curious if someone could link to things / explain, and (2) fyi ('stephenr) last write wins based on timestamp is a thing im mysql world as well (though again maybe set of options / different conflict resolution methods available is larger in mysql?) [1]: https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-replication-conflict-resolution.html https://dev.mysql.com/doc/refman/8.4/en/mysql-cluster-replic... [2]: https://dev.mysql.com/blog-archive/enhanced-conflict-resolution-with-mysql-cluster-active-active-replication/ https://dev.mysql.com/blog-archive/enhanced-conflict-resolut... (nice writeup, maybe outdated idk?)

stephenr 1y ago
For reference those two pages are both about NDB cluster. The two "options" I was referring to are MySQL group replication and the Galera replication plugin for MySQL. Both provide synchronous replication, so the write either succeeds to a majority of the cluster or is rejected.
- wfn 1y ago
  Understood, thanks! I wasn't even sure where to look - thank you

agnivade 1y ago

Just for my own understanding, could you clarify why you think "last write wins" is a recipe for disaster?

stephenr 1y ago
Because two simultaneous writes mean some change is just lost, without feedback to the writer.