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

["Apache Spark (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-9460?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14647046#comment-14647046 ] 

Apache Spark commented on SPARK-9460:
-------------------------------------

User 'rxin' has created a pull request for this issue:
https://github.com/apache/spark/pull/7765

> 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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