alamb commented on code in PR #7463:
URL: https://github.com/apache/arrow-rs/pull/7463#discussion_r2073584836
##########
arrow-select/src/filter.rs:
##########
@@ -656,29 +653,44 @@ where
(start, end, len)
}
- /// Extends the in-progress array by the indexes in the provided iterator
- fn extend_idx(&mut self, iter: impl Iterator<Item = usize>) {
+ fn extend_offsets_idx(&mut self, iter: impl Iterator<Item = usize>) {
self.dst_offsets.extend(iter.map(|idx| {
let start = self.src_offsets[idx].as_usize();
let end = self.src_offsets[idx + 1].as_usize();
let len = OffsetSize::from_usize(end - start).expect("illegal
offset range");
self.cur_offset += len;
- self.dst_values
- .extend_from_slice(&self.src_values[start..end]);
+
self.cur_offset
}));
+ self.dst_values.reserve_exact(self.cur_offset.as_usize());
}
- /// Extends the in-progress array by the ranges in the provided iterator
- fn extend_slices(&mut self, iter: impl Iterator<Item = (usize, usize)>) {
+ /// Extends the in-progress array by the indexes in the provided iterator
+ fn extend_idx(&mut self, iter: impl Iterator<Item = usize>) {
+ for idx in iter {
+ let start = self.src_offsets[idx].as_usize();
+ let end = self.src_offsets[idx + 1].as_usize();
+ self.dst_values
+ .extend_from_slice(&self.src_values[start..end]);
+ }
+ }
+
+ fn extend_offsets_slices(&mut self, iter: impl Iterator<Item = (usize,
usize)>, count: usize) {
+ self.dst_offsets.reserve_exact(count);
for (start, end) in iter {
// These can only fail if `array` contains invalid data
for idx in start..end {
let (_, _, len) = self.get_value_range(idx);
self.cur_offset += len;
- self.dst_offsets.push(self.cur_offset); // push_unchecked?
+ self.dst_offsets.push(self.cur_offset);
}
+ }
+ self.dst_values.reserve_exact(self.cur_offset.as_usize());
Review Comment:
I think it would make sense for this call to reserve_exact to be a part of
`extend_idx` (which is what actually extends the values). Otherwise I think it
is quite tricky to understand that the performance of `extend_idx` is relying
on calling `extend_offsts_slices` first
Since they are now always called in a pair `extend_offsets_slices` and
`extend_slices` I don't think this would change anything functionally but it
would make the code easier for me to understand (even though you would also
have to pass `count` to the extend_idx was well
Another alternative might be to make a function `fn reserve_exact` that to
make the allocations explicit
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