TsukiokaKogane commented on code in PR #66849:
URL: https://github.com/apache/doris/pull/66849#discussion_r3801775473
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be/src/storage/iterator/block_reader.cpp:
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@@ -95,6 +110,10 @@ Status BlockReader::_ensure_binlog_column_pos(const Block&
src_block) {
const uint32_t col_num = src_block.columns();
_before_column_idx.resize(col_num);
+ std::iota(_before_column_idx.begin(), _before_column_idx.end(), 0);
+ std::vector<bool> is_before_value_column(col_num, false);
Review Comment:
新增两处宽表 O(C²) 初始化
[olap_scanner.cpp:506](https://github.com/apache/doris/blob/56a134171dca2848291e92b4a733c0ed9e63967a/be/src/exec/scan/olap_scanner.cpp#L506)：为每列执行一次
std::find。
[block_reader.cpp:124](https://github.com/apache/doris/blob/56a134171dca2848291e92b4a733c0ed9e63967a/be/src/storage/iterator/block_reader.cpp#L124)：为每列调用一次线性
get_position_by_name()。
应使用 dense bitmap/hash set 维护已选择列，并一次性构造名称或 ordinal 映射，把两处降为 O(C)。
建议优化一下 宽表 O(C²) 初始化的部分
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