adonis0147 commented on code in PR #10386:
URL: https://github.com/apache/doris/pull/10386#discussion_r905871733
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be/src/olap/rowset/segment_v2/segment_iterator.cpp:
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@@ -872,9 +872,11 @@ Status SegmentIterator::_read_columns_by_index(uint32_t
nrows_read_limit, uint32
_read_columns(_first_read_column_ids, _current_return_columns,
rows_to_read));
_cur_rowid += rows_to_read;
if (set_block_rowid) {
- for (uint32_t rid = range_from; rid < range_to; rid++) {
- _block_rowids[nrows_read++] = rid;
- }
+ // Here use std::iota is better performance than for-loop, maybe
for-loop is not vectorized
Review Comment:
I compared both assembly code generated by GCC 12.1 + O3, the difference
between them is subtle. Compiler optimizes both loops by SSE registers.
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