xiaokang commented on code in PR #10694:
URL: https://github.com/apache/doris/pull/10694#discussion_r937402867
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be/src/olap/rowset/segment_v2/segment_iterator.cpp:
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@@ -915,7 +959,8 @@ Status SegmentIterator::_read_columns_by_index(uint32_t
nrows_read_limit, uint32
} else {
nrows_read += rows_to_read;
}
- } while (nrows_read < nrows_read_limit);
+ // if _opts.read_orderby_key_reverse is true, only read one range for
fast reverse purpose
Review Comment:
OK. It's related to the code 'reverse block row order' at the end of
SegmentIterator::next_batch.
If we read more than one range in reverse order here, such as range10 with
rows 9000 ~ 10000 and range9 with rows 8000 ~ 9000, the block will contain
non-continous ordered rows 9000 ~ 10000,8000 ~ 9000. Then the reverse block at
the end of next_batch will get rows 9000 ~ 8000,10000 ~ 9000. It's not totally
in reversed order.
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