Concurrency, Rails and PostgreSQL vs. MySQL

Hi,

Let's say we have users concurrently performing the following queries
inside a transaction (example taken directly from PostgreSQL site):

User A:

Alexei, I believe this is the same message you posted two days ago. Did you see the replies?

In short: both databases do what you expect. Use a single update statement to avoid issues with concurrency, locking, and dirty reads.

Best,
jeremy

Alexei, I believe this is the same message you posted two days ago. Did you
see the replies?

Yes, I've seen the replies - I have no idea, why the same message got
posted once again, days later :confused:

Thank you very much for your help!

Alexei