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Date: Wed, 12 Apr 2017 09:15:41 +0000 (UTC)
From: "Xavier (JIRA)" <jira@apache.org>
To: crunch-dev@incubator.apache.org
Message-ID: <JIRA.13062890.1491829808000.263782.1491988541841@Atlassian.JIRA>
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Subject: [jira] [Updated] (CRUNCH-642) Enable numReducers option for methods
 in Distinct
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archived-at: Wed, 12 Apr 2017 09:15:48 -0000


     [ https://issues.apache.org/jira/browse/CRUNCH-642?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Xavier updated CRUNCH-642:
--------------------------
    Attachment: CRUNCH-642-Enable-GroupingOptions-for-Distinct-operations.patch

Hey [~joshwills],

I noticed my change introduces a major bug when running the distinct operation with a non-memory PCollection.
My apologies for this terrible mistake. In attachment is an additional patch that solves this by passing along the GroupOptions
object instead of a numReducers integer. This will be more flexible and avoids bugs like this popping up. I also added
tests (both unit and integration tests) to ensure the fix is now working.

> Enable numReducers option for methods in Distinct
> -------------------------------------------------
>
>                 Key: CRUNCH-642
>                 URL: https://issues.apache.org/jira/browse/CRUNCH-642
>             Project: Crunch
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 0.14.0
>            Reporter: Xavier
>            Assignee: Josh Wills
>            Priority: Trivial
>         Attachments: CRUNCH-642-Enable-GroupingOptions-for-Distinct-operations.patch, CRUNCH-642.patch
>
>
> The {{groupByKey}} invocation in the {{Distinct}} class currently uses the default  (recommended) number of reducers without providing an option to override this:
> {code}
> public static <S> PCollection<S> distinct(PCollection<S> input, int flushEvery) {
>   Preconditions.checkArgument(flushEvery > 0);
>   PType<S> pt = input.getPType();
>   PTypeFamily ptf = pt.getFamily();
>   return input
>       .parallelDo("pre-distinct", new PreDistinctFn<S>(flushEvery, pt), ptf.tableOf(pt, ptf.nulls()))
>       .groupByKey()
>       .parallelDo("post-distinct", new PostDistinctFn<S>(), pt);
> }
> {code}
> Would it be possible to enhance this method such that it is possible to customize the number of reducers? Either explicitly or via a {{GroupingOptions}} object.


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