Method invoke_with_args

datafusion/functions/src/unicode/lpad.rs:110–173

(&self, args: ScalarFunctionArgs)

    }

    fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
        let ScalarFunctionArgs {
            args, number_rows, ..
        } = args;

        const MAX_SCALAR_TARGET_LEN: usize = 16384;

        // If target_len and fill (if specified) are constants, use the scalar
        // fast path.
        if let Some(target_len) = try_as_scalar_i64(&args[1]) {
            let target_len: usize = match usize::try_from(target_len) {
                Ok(n) if n <= i32::MAX as usize => n,
                Ok(n) => {
                    return exec_err!(
                        "lpad requested length {n} too large, maximum allowed length is {}",
                        i32::MAX
                    );
                }
                Err(_) => 0, // negative → 0
            };

            let fill_str = if args.len() == 3 {
                try_as_scalar_str(&args[2])
            } else {
                Some(" ")
            };

            // Skip the fast path for very large `target_len` values to avoid
            // consuming too much memory. Such large padding values are uncommon
            // in practice.
            if target_len <= MAX_SCALAR_TARGET_LEN
                && let Some(fill) = fill_str
            {
                let string_array = args[0].to_array_of_size(number_rows)?;
                let result = match string_array.data_type() {
                    Utf8View => lpad_scalar_args::<_, i32>(
                        string_array.as_string_view(),
                        target_len,
                        fill,
                    ),
                    Utf8 => lpad_scalar_args::<_, i32>(
                        string_array.as_string::<i32>(),
                        target_len,
                        fill,
                    ),
                    LargeUtf8 => lpad_scalar_args::<_, i64>(
                        string_array.as_string::<i64>(),
                        target_len,
                        fill,
                    ),
                    other => {
                        exec_err!("Unsupported data type {other:?} for function lpad")
                    }
                }?;
                return Ok(ColumnarValue::Array(result));
            }
        }