Eng 6012 inexists sp

I don't understand why this code wants to be bypassed for ! isDQLStmt.
I am getting a little confused by the attempt to handle both "expr subqueries" and "from subqueries" in one generalized hasSubquery code path.
I think it would be clearer to handle them separately.
For one thing, there's no reason why order non-determinism of IN/EXISTS subqueries should have any effect.

Also, for the sake of further simplicity in ruling out content non-determinism, I am perfectly comfortable with our initial offering simply erroring out of the planner on ANY use case of IN/EXISTS with a limit or offset INSIDE the subquery -- that's just too strange for me to worry about unless/until I actually hear of it from the field.
I guess that leaves us with just the from subquery case to check for determinism.

Scalar subquery will raise a similar content determinism question -- and I'm only seeing SLIGHTLY more motivation to support internal LIMIT/OFFSET for that case than for the IN/EXISTS case.