fn dp_head(parent: &str) -> Vec<Field>Expand description
Columns every data point table has, in the same order, so that a temporal filter is the same code against any of the four.
start_time_unix_nano is nullable and, importantly, does not contribute
to the block’s time range. For a cumulative metric it is process start, which
can be hours or days before the point; folding it in would make every block
claim to cover that whole span and destroy time-based pruning for the one
signal that needs it most.