[jira] [Created] (ORC-976) Optimize compute zigZagLiterals

["Yiqun Zhang (Jira)" <ji...@apache.org>]

Yiqun Zhang created ORC-976:
-------------------------------

             Summary: Optimize compute zigZagLiterals
                 Key: ORC-976
                 URL: https://issues.apache.org/jira/browse/ORC-976
             Project: ORC
          Issue Type: Improvement
          Components: Java
    Affects Versions: 1.7.0
            Reporter: Yiqun Zhang
             Fix For: 1.7.0



{code:java}
  private void computeZigZagLiterals() {
    // populate zigzag encoded literals
    long zzEncVal = 0;
    for (int i = 0; i < numLiterals; i++) {
      if (signed) {
        zzEncVal = utils.zigzagEncode(literals[i]);
      } else {
        zzEncVal = literals[i];
      }
      zigzagLiterals[i] = zzEncVal;
    }
  }
{code}

Avoid conditional judgments in loops. 
The unsigned case can use literals instead of zigzagLiterals. The number of copies is proportional to the amount of user writes, which optimizes write performance.




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