I wasn't sure if this question should be posted here or on regular user list, considering the way statements are generated and possible connections with internal functionality.

I understand the explanations. I should have checked the explain feature myself. I think that I expected the optimizer to notice a constant expression and evaluate it before choosing which real columnar operation needs to be performed (obviously only one). Instead all members are evaluated, the whole explain statement is self-explanatory, indeed. (a delayed bat evaluation mechanism would have helped, I guess, for this case)

I use capi intensively, but for string columns the capi memory management can be a serious limitation for large sets.

Anyway, your answer is very helpful for me, it makes me consider adjusting my approach from a straight translation into one SQL statement into using an intermediary language that would build the optimal statement instead of stretching the SQL to get what I need.

Thank you,