Oracle DBA here who hates their licensing, practices, etc. as much as the next guy, but I have to hand it to their query optimization. I've seen their optimizer get better with every major release, and yes, regression testing will always turn up a few problems but Oracle gives you the best tools to analyze and override the decisions that the optimizer is making when necessary (and I'm not just talking about basic hints here)
So, you changed code and didn't test it. Yup, definitely Oracle's fault.
Sometimes you just aren't going to pick up this sort of thing in testing as you'll only know about it under full production load. Their CBO is pretty powerful, but by and large it's often difficult to know why it makes certain decisions. And that's even when you use their full suite of profiling tools!
That's not even really a CBO issue. But I hear your pain :-)
no, it really is not.
I agree, but the point is that they are getting worse. Their cloud shift is not panning out as well as they wanted, I think, and they are actually opening opportunities for competitors: if you have to make significant efforts to migrate your existing solutions, you might as well move somewhere nicer. And by basically threatening their own partner ecosystems (which won't be needed in the new oracle-cloud era), they're losing steam in sales and presales.
(Of course, it doesn't help that Safe Harbor first and Privacy Shield now have been shot down, so European businesses are not keen on moving to US-based clouds. The sort of businesses Oracle pines for, does care about these things.)
Forever and a day. Oracle sells to managers and executives and are very, very good at it.
Your opinion of the company as a developer or engineer has literally no relevance.