I should have copied and saved its suggestion, but the DC AI offered another approach that also required some string manipulation. :-)

Hi again Robert,

I also would have expected the plans for both 18 and 19 to be the same, but "quelle surprise!":

18: Beautiful, expected plan:

19: What? I must have messed something up in the evolution of this class to have such an expensive plan that produces incorrect results:

I'll investigate further to figure out how to address that second plan, but any input from you or others would be welcome.

Thanks and best regards.

Thank you, Robert (great to hear from you)! I will give those a shot to see what's going on and potentially clear cached queries if nothing obviously problematic shows up in the plans.

Best regards, Jean