[jira] [Created] (SPARK-9460) Avoid byte array allocation in StringPrefixComparator

["Reynold Xin (JIRA)" <ji...@apache.org>]

Reynold Xin created SPARK-9460:
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             Summary: Avoid byte array allocation in StringPrefixComparator
                 Key: SPARK-9460
                 URL: https://issues.apache.org/jira/browse/SPARK-9460
             Project: Spark
          Issue Type: Sub-task
          Components: SQL
            Reporter: Reynold Xin


StringPrefixComparator converts the long values back to byte arrays in order to compare them. We should be able to optimize this to compare the longs directly, rather than turning the longs into byte arrays and comparing them byte by byte. 

{code}
    public int compare(long aPrefix, long bPrefix) {
      // TODO: can done more efficiently
      byte[] a = Longs.toByteArray(aPrefix);
      byte[] b = Longs.toByteArray(bPrefix);
      for (int i = 0; i < 8; i++) {
        int c = UnsignedBytes.compare(a[i], b[i]);
        if (c != 0) return c;
      }
      return 0;
    }
{code}



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