[jira] [Created] (HIVE-24670) DeleteReaderValue should not allocate empty vectors for delete delta files

["Ádám Szita (Jira)" <ji...@apache.org>]

Ádám Szita created HIVE-24670:
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             Summary: DeleteReaderValue should not allocate empty vectors for delete delta files
                 Key: HIVE-24670
                 URL: https://issues.apache.org/jira/browse/HIVE-24670
             Project: Hive
          Issue Type: Improvement
            Reporter: Ádám Szita
            Assignee: Ádám Szita


If delete delta caching is turned off, the plain record reader inside DeleteReaderValue allocates a batch with a schema that is equivalent to that of an insert delta.

This is unnecessary as the struct part in a delete delta file is always empty. In cases where we have many delete delta files (e.g. due to compaction failures) and a wide table definition (e.g. 200+ cols) this puts a significant amount of memory pressure on the executor, while these empty structures will never be filled or otherwise utilized.

I propose we specify an ACID schema with an empty struct part to this record reader to counter this.



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