xiaokang opened a new pull request, #9741:
URL: https://github.com/apache/incubator-doris/pull/9741

   fix column reader compress codec unsafe problem by moving codec from shared 
reader to unshared iterator
   
   # Proposed changes
   
   Issue Number: close #9706, which was introduced by 
https://github.com/apache/incubator-doris/pull/9566
   
   ## Problem Summary:
   
   ColumnReader is not thread safe and its `BlockCompressionCodec 
_compress_codec`  can be shared by multiple threads. But #9566 changed 
BlockCompressionCodec to be NOT thread safe for very promising performance 
reason.
   
   The solution is to move _compress_codec from shared ColumnReader to unshared 
FileColumnIterator, and the same to IndexedColumnReader & IndexedColumnIterator.
   
   The solution is better than the previous one #9714, which use thread_local 
compress/decompress context objects.
   
   BTW, add a thread unsafe notice for BlockCompressionCodec.
   
   ## Checklist(Required)
   
   1. Does it affect the original behavior: (No)
   2. Has unit tests been added: (No)
   3. Has document been added or modified: (No Need)
   4. Does it need to update dependencies: (No)
   5. Are there any changes that cannot be rolled back: (No)
   
   ## Further comments
   
   If this is a relatively large or complex change, kick off the discussion at 
[[email protected]](mailto:[email protected]) by explaining why you 
chose the solution you did and what alternatives you considered, etc...
   


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