jorgecarleitao edited a comment on pull request #8740:
URL: https://github.com/apache/arrow/pull/8740#issuecomment-731845713
Cool!
IMO we want to "take" from different arrays depending on a set of boolean
conditions. My recommendation is to use `MutableDataArray` API that we also
use in the Join and that was though through exactly for this use-case.
Something like
```rust
let boolean_conditions: Vec<BooleanArray> = <args>
let first_non_null: Vec<usize> = first_true(boolean_conditions) // index
from 0 to boolean_conditions.len() (inclusive, last represents the "else")
let capacity = boolean_conditions[0].len();
let arrays_data = arrays.iter().map(|array|
array.data_ref()).collect::<Vec<_>>();
let mutable = MutableDataArray::new(&arrays_data, capacity);
for row in boolean_conditions[0].len() {
let index = first_non_null[row];
if index == boolean_conditions.len() {
// the else case
mutable.extend_null(index); // this function is still not available
in master, but I have a branch with it
} else {
// take the slice `[row,row+1[` from array "index".
mutable.extend_from_slice(index, row, row + 1);
}
}
return make_array(Arc::new(mutable.freeze()));
```
the advantage of this is that it works for all types except struct.
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