I'm told that MySQL replication blows Postgres out of the water by my company's data team, but they could just be biased since that is their area of expertise. I work on server code and don't really have much familiarity with the operations of running replica chains.

Postgres seems like a better choice for personal projects since it has a lot of nifty features. I'm also wary of Oracle, but that's my own attitude talking. For a startup eventually wanting to scale, would the better choice be to use MySQL out of the gates? Am I being mislead about Postgres clusters and availability?

Serious (naive) question; not wanting to start a flame war.

dijit

Having ran MySQL in prod for a decade and PostgreSQL in prod for half a decade I can say without doubt that your data team is telling fibs.

Firstly we consider that there are multiple replication possibilities of both technologies- however I'm going to assume the defaults because that's pretty much what everyone uses except if there's an actual case for using something else. It's the exception.

But by default MySQL uses statement based replication (in a weird binary format with log positions and stuff) and postgresql does logical replication (as in, you transmit the binary differences of what you'll be doing to the replica's database files directly and the replica just follows along)

Both of these approaches have trade-offs depending on what you want.

Statement based replication is great if you want to have _different_ datasets on each side, You can transform the data or remove huge chunks of it on a slave and use it for a dedicated purpose. However that applies the other way, you can never really be 100% sure that your replica looks exactly like your master.

this bit me a few times with MySQL when I assumed that because the replica was 'up to date' with the master and it was set to read only, that the data had integrity- it absolutely did not.

antoncohen

I don't think the claim of MySQL replication being better is related to statement vs. row vs. binary diff. I think it is about the tooling and community knowledge about replication, and about running MySQL in large scale production environments in general.

MySQL is run more often at extremely large scale (Facebook, YouTube, Twitter, Dropbox, etc.) than Postgres. That results in very battle tested and/or featureful tooling like orchestrator (https://github.com/github/orchestrator), MHA (https://github.com/yoshinorim/mha4mysql-manager), ProxySQL (http://www.proxysql.com/), and gh-ost (https://github.com/github/gh-ost), along knowledge and best practices shared by those organization.