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  1. Apache Drill
  2. DRILL-4530

Improve metadata cache performance for queries with single partition

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Details

    • Improvement
    • Status: Closed
    • Major
    • Resolution: Fixed
    • 1.6.0
    • 1.8.0
    • None

    Description

      Consider two types of queries which are run with Parquet metadata caching:

      query 1:
      SELECT col FROM  `A/B/C`;
      
      query 2:
      SELECT col FROM `A` WHERE dir0 = 'B' AND dir1 = 'C';
      

      For a certain dataset, the query1 elapsed time is 1 sec whereas query2 elapsed time is 9 sec even though both are accessing the same amount of data. The user expectation is that they should perform roughly the same. The main difference comes from reading the bigger metadata cache file at the root level 'A' for query2 and then applying the partitioning filter. query1 reads a much smaller metadata cache file at the subdirectory level.

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            amansinha100 Aman Sinha
            amansinha100 Aman Sinha
            Rahul Kumar Challapalli Rahul Kumar Challapalli
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