The best example of this is Salesforce, which has their own proprietary SQL-like query language that's clearly just a crappy front end to generate raw SQL to feed their Oracle DB's. Without Oracle's per-tenant limit this would be far too risky because of idiots making bad queries.
An better solution these days is to put each tenant in a Postgres container and let the OS control resource limits for them, but this wasn't an option until recently.
Killing connections can be done in postgresql too. The reason for sf to be on oracle is probably history.
A few things I've found great in Oracle that aren't (AFAIK) available in PG:
- Straight better/more reliable performance on average
- More advanced parallel queries (obviously this is changing in PG right now)
- Flashback queries
- Better materialized views
- Plan stability (maintains predictable query performance, rather than the nasty jumps you sometimes see when plans change)
- Better clustering story (RAC is super expensive but pretty good)
It was actually good and very easy to activate. If you did activate it though you could expect a sizable extra invoice after next audit.