zuochunwei commented on a change in pull request #7852:
URL: https://github.com/apache/incubator-doris/pull/7852#discussion_r791334747
##########
File path: be/src/olap/rowset/segment_v2/segment_iterator.cpp
##########
@@ -872,13 +867,13 @@ Status SegmentIterator::next_batch(vectorized::Block*
block) {
RETURN_IF_ERROR(_init(true));
_inited = true;
if (!_vec_pred_column_ids.empty() ||
!_short_cir_pred_column_ids.empty()) {
- _block_rowids.reserve(_opts.block_row_max);
+ _block_rowids.resize(_opts.block_row_max);
Review comment:
reverve just alloc memory for optimization reason.
there is one basic rule: any reserve calls can be removed, this removing
operation will not influence the correctness of result.
according this rule, if we remove this _block_rowids.reserve(), the will
crash, so we should use resize instead.
##########
File path: be/src/olap/rowset/segment_v2/segment_iterator.cpp
##########
@@ -872,13 +867,13 @@ Status SegmentIterator::next_batch(vectorized::Block*
block) {
RETURN_IF_ERROR(_init(true));
_inited = true;
if (!_vec_pred_column_ids.empty() ||
!_short_cir_pred_column_ids.empty()) {
- _block_rowids.reserve(_opts.block_row_max);
+ _block_rowids.resize(_opts.block_row_max);
Review comment:
reserve只是预分配内存，是而且只是性能的考虑，代码中任何调用reserve()的地方应该可以被删除，而不会影响正确性。
比如vector，调用reserve后不会改变vector的size，随后的at(index)会崩，operator[index]的行为也依赖于实现，所以，这个地方用resize更合适
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