HaoYang670 opened a new issue #1373:
URL: https://github.com/apache/arrow-rs/issues/1373
**Is your feature request related to a problem or challenge? Please describe
what you are trying to do.**
The function `min_max_string` does some unnecessary checks when `null_count
> 0 `. For example, we don't need to check `has_value` in every loop because it
will always be `true` after the first loop.
```rust
if null_count == 0 {
n = array.value(0);
for i in 1..data.len() {
let item = array.value(i);
if cmp(n, item) {
n = item;
}
}
} else {
n = "";
let mut has_value = false;
for i in 0..data.len() {
let item = array.value(i);
if data.is_valid(i) && (!has_value || cmp(n, item)) {
has_value = true;
n = item;
}
}
}
```
https://github.com/apache/arrow-rs/blob/master/arrow/src/compute/kernels/aggregate.rs#L55-L64
Apart from that, I want this function to be cleaned up because the "for
loops" here are not pretty.
**Describe the solution you'd like**
1. Performance should be improved when `null_count > 0`
2. No performance penalty is introduced in other cases
3. clean up the code. Maybe use some FP skills
**Describe alternatives you've considered**
We can also replace `array.value(i)` by `array.value_unchecked(i)`. But it
will introduce some "unsafe", so I am not sure.
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