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From amansinha100 <...@git.apache.org>
Subject [GitHub] drill pull request: DRILL-3884: Fix lower parallelization issues w...
Date Fri, 02 Oct 2015 00:11:49 GMT
Github user amansinha100 commented on a diff in the pull request:

    https://github.com/apache/drill/pull/185#discussion_r40981727
  
    --- Diff: contrib/storage-hive/core/src/main/java/org/apache/drill/exec/store/hive/HiveScan.java
---
    @@ -319,16 +319,12 @@ public ScanStats getScanStats() {
             estRowCount = data/1024;
           }
     
    -      // Hive's native reader is neither memory efficient nor fast. If the rowcount is
below
    -      // HIVE_SERDE_SCAN_OVERHEAD_FACTOR, make sure it is at least HIVE_SERDE_SCAN_OVERHEAD_FACTOR
to enable the planner
    -      // to choose HiveDrillNativeParquetScan. Due to the project on top of HiveDrillNativeParquetScan,
we end up
    -      // choosing the HiveScan instead of HiveDrillNativeParquetScan if the cost is too
low.
    -      if (estRowCount <= HIVE_SERDE_SCAN_OVERHEAD_FACTOR) {
    -        estRowCount = HIVE_SERDE_SCAN_OVERHEAD_FACTOR;
    -      }
    +      // Hive's native reader is neither memory efficient nor fast. Increase the CPU
cost
    +      // by a factor to let the planner choose HiveDrillNativeScan over HiveScan with
SerDes.
    +      float cpuCost = 1 * HIVE_SERDE_SCAN_OVERHEAD_FACTOR;
    --- End diff --
    
    I am thinking this cost should include the number of columns as well...suppose there are
lots of columns(e.g 500), we want both types of plans to be equally penalized.  


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