pub fn arity(&self) -> usize {
        self.relation_desc
            .as_ref()
            .map(|desc| desc.typ().column_types.len())
            .unwrap_or(0)
    }
/// Reports the number of columns in the statement's result set, or zero if
/// the statement does not return rows.
Reports the number of columns in the statement's result set, or zero if
the statement does not return rows.
Reports the number of columns in the statement ' s result set or zero if the statement does not return rows .
pub fn arity(&self) -> usize {
        self.relation_desc
            .as_ref()
            .map(|desc| desc.typ().column_types.len())
            .unwrap_or(0)
    }
pub fn arity ( & self ) -> usize { self . relation_desc . as_ref ( ) . map ( | desc | desc . typ ( ) . column_types . len ( ) ) . unwrap_or ( 0 ) }
Reports the number of columns in the statement's result set, or zero if
the statement does not return rows.
Reports the number of columns in the statement ' s result set or zero if the statement does not return rows .
&self
&self