pub fn define(model: &Model, text: &str, id: u32) -> Result<MeasureRow>Expand description
Validate a Target = expr definition against model and return the
catalog row for the new derived measure id. Its categories are the
engine-inferred result dimensions (an OVER aggregation drops the
aggregated category), which is exactly the result table’s shape. An
existing target is an error (define_measure can replace it).