Function generate_subscripts_array

src/expr/src/relation/func.rs:3111–3145

(
    a: Datum,
    dim: i32,
)

}

fn generate_subscripts_array(
    a: Datum,
    dim: i32,
) -> Result<Box<dyn Iterator<Item = (Row, Diff)>>, EvalError> {
    if dim <= 0 {
        return Ok(Box::new(iter::empty()));
    }

    match a.unwrap_array().dims().into_iter().nth(
        (dim - 1)
            .try_into()
            .map_err(|_| EvalError::Int32OutOfRange((dim - 1).to_string().into()))?,
    ) {
        Some(requested_dim) => {
            let lower_bound: i32 = requested_dim.lower_bound.try_into().map_err(|_| {
                EvalError::Int32OutOfRange(requested_dim.lower_bound.to_string().into())
            })?;
            // The subscripts run from the lower bound to the upper bound,
            // inclusive. The upper bound is `lower_bound + length - 1`.
            let length: i32 = requested_dim
                .length
                .try_into()
                .map_err(|_| EvalError::Int32OutOfRange(requested_dim.length.to_string().into()))?;
            let upper_bound = lower_bound.checked_add(length - 1).ok_or_else(|| {
                EvalError::Int32OutOfRange(requested_dim.length.to_string().into())
            })?;
            Ok(Box::new(generate_series::<i32>(
                lower_bound,
                upper_bound,
                1,
            )?))
        }
        None => Ok(Box::new(iter::empty())),
    }
}

fn unnest_array<'a>(a: Datum<'a>) -> impl Iterator<Item = (Row, Diff)> + 'a {
    a.unwrap_array()