mapleFU commented on code in PR #46463:
URL: https://github.com/apache/arrow/pull/46463#discussion_r2106987170
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cpp/src/parquet/metadata.cc:
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@@ -334,8 +335,19 @@ class ColumnChunkMetaData::ColumnChunkMetaDataImpl {
return possible_geo_stats_ != nullptr && possible_geo_stats_->is_valid();
}
+ inline std::shared_ptr<EncodedStatistics> encoded_statistics() const {
+ return is_stats_set() ? possible_encoded_stats_ : nullptr;
+ }
+
inline std::shared_ptr<Statistics> statistics() const {
- return is_stats_set() ? possible_stats_ : nullptr;
+ if (is_stats_set()) {
+ // Because we are modifying possible_stats_ in a const method
+ const std::lock_guard<std::mutex> guard(stats_mutex_);
+ if (possible_stats_ == nullptr) {
+ possible_stats_ = MakeColumnStats(*column_metadata_, descr_);
+ }
+ }
+ return possible_stats_;
Review Comment:
I think this is a bit dangerous ( user might merely touch this), assume
thread1, thread2 calls `statistics`
1. thread1 calls `is_stats_set`, creates the `possible_encoded_stats_`,
return
2. thread2 calls `is_stats_set`, return `possible_stats_` ( which is empty )
3. thread1 construct the `possible_stats_`
Seems 2/3 has concurrency issues?
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