[GitHub] [arrow-rs] alamb opened a new issue #75: [rust][datafusion] optimize count(*) queries on parquet sources

[GitBox <gi...@apache.org>]

alamb opened a new issue #75:
URL: https://github.com/apache/arrow-rs/issues/75


   *Note*: migrated from original JIRA: https://issues.apache.org/jira/browse/ARROW-8902
   
   Currently, as far as I can tell, when you perform a `select count(*) from dataset` in datafusion against a parquet dataset, the way this is implemented is by doing a scan on column 0, and counting up all of the rows (specifically I think it counts the # of rows in each batch).
   
    
   
   However, for the specific case of just counting _everythign_ in a parquet file, you can just read the rowcount from the footer metadata, so it's O(1) instead of O(n)


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[GitHub] [arrow-rs] alamb commented on issue #75: [rust][datafusion] optimize count(*) queries on parquet sources

[GitBox <gi...@apache.org>]

alamb commented on issue #75:
URL: https://github.com/apache/arrow-rs/issues/75#issuecomment-826803085


   wrong repo


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[GitHub] [arrow-rs] alamb closed issue #75: [rust][datafusion] optimize count(*) queries on parquet sources

[GitBox <gi...@apache.org>]

alamb closed issue #75:
URL: https://github.com/apache/arrow-rs/issues/75


   


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