Type Alias IntExtractor 

pub type IntExtractor = Box<dyn Fn(&Row) -> i64 + Send + Sync>;

Closure that extracts an i64-coerced column value (for aggregate inputs). Returns 0 for NULL / non-numeric — same handling as SQL’s implicit-coalesce-to-zero in SUM / AVG.

Aliased Type

pub struct IntExtractor(/* private fields */);