[GitHub] [doris] mrhhsg commented on a diff in pull request #10386: [improvement]Use std::iota to set values of _block_rowids in SegmentIterator::_read_columns_by_index

[GitBox <gi...@apache.org>]

mrhhsg commented on code in PR #10386:
URL: https://github.com/apache/doris/pull/10386#discussion_r905868074


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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:
   There are two reasons why this loop can not be vectorized:
   1. `nrows_read` is reference
   2. `nrows_read` is unsigned



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