[jira] [Resolved] (TAJO-976) HashPartitioner doesn't make desired number of partitions infrequently.

["Hyunsik Choi (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/TAJO-976?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Hyunsik Choi resolved TAJO-976.
-------------------------------

    Resolution: Fixed

committed it to master branch.

> HashPartitioner doesn't make desired number of partitions infrequently.
> -----------------------------------------------------------------------
>
>                 Key: TAJO-976
>                 URL: https://issues.apache.org/jira/browse/TAJO-976
>             Project: Tajo
>          Issue Type: Improvement
>            Reporter: Hyoungjun Kim
>            Assignee: Hyoungjun Kim
>            Priority: Minor
>
> If the number desired partition is a multiples of 31, HashPartitioner doesn't make desired number of partitions. I tested with the following code.
> {code}
> Random rand = new Random();
> String[][] data = new String[1000][];
> for (int i = 0; i < 1000; i++) {
>   data[i] = new String[]{ String.valueOf(rand.nextInt(1000)), String.valueOf(rand.nextInt(1000)), String.valueOf(rand.nextInt(1000))};
> }
> int[] testNumPartitions = new int[]{31, 62, 124, 32, 63, 125};
> for (int index = 0; index <  testNumPartitions.length; index++) {
>   Set<Integer> ids = new TreeSet<Integer>();
>   for (int i = 0; i < data.length; i++) {
>     VTuple vtuple = new VTuple(new Datum[]{new TextDatum(data[i][0]), new TextDatum(data[i][1]), new TextDatum(data[i][2])});
>     int hashValue = vtuple.hashCode();
>     int partitionId = (hashValue & Integer.MAX_VALUE) % testNumPartitions[index];
>     ids.add(partitionId);
>   }
>   System.out.println("Expected partition num: " + testNumPartitions[index] + ", real partition num:" + ids.size());
> }
> {code}
> {noformat}
> Expected partition num: 31, real partition num:10
> Expected partition num: 62, real partition num:20
> Expected partition num: 124, real partition num:40
> Expected partition num: 32, real partition num:32
> Expected partition num: 63, real partition num:63
> Expected partition num: 125, real partition num:125
> {noformat}



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