[GitHub] [spark] yabola commented on pull request #39950: [SPARK-42388][SQL] Avoid parquet footer reads twice when no filters in vectorized reader

["yabola (via GitHub)" <gi...@apache.org>]

yabola commented on PR #39950:
URL: https://github.com/apache/spark/pull/39950#issuecomment-1451913404

   @sunchao Sorry, it might be a mistake. We should read schema in footer meta first to get which filters need to be pushed down. After that we set pushdown info [codes](https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetFileFormat.scala#L261)  and read filtered RowGroups.
   
   So I think it might have to read footer twice if having filters. But we can read footer once when no filter is needed pushdown.
   
   I think It will be useful when scanning joined tables (filter condition is only on the other side of the join table and filter is none in the joined table).  It can avoid reading much footer when there are many  joined tables.


-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org


---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org
For additional commands, e-mail: reviews-help@spark.apache.org