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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (APEXMALHAR-2015) Projection Operator
Date Thu, 17 Mar 2016 13:53:33 GMT

    [ https://issues.apache.org/jira/browse/APEXMALHAR-2015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15199552#comment-15199552
] 

ASF GitHub Bot commented on APEXMALHAR-2015:
--------------------------------------------

GitHub user pradeepdalvi opened a pull request:

    https://github.com/apache/incubator-apex-malhar/pull/217

    APEXMALHAR-2015: Projection Operator & its unit tests

     - Projection Operator
     - Unit tests for select/drop fields & projection operator

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/pradeepdalvi/incubator-apex-malhar master

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/incubator-apex-malhar/pull/217.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #217
    
----
commit 2cb5234719f49e336e4797bcbf041e02f4279a98
Author: Pradeep A. Dalvi <pradeep.dalvi@datatorrent.com>
Date:   2016-03-16T12:09:17Z

    APEXMALHAR-2015: Projection Operator & its unit tests
     - Projection Operator
     - Unit tests for select/drop fields & projection operator

----


> Projection Operator
> -------------------
>
>                 Key: APEXMALHAR-2015
>                 URL: https://issues.apache.org/jira/browse/APEXMALHAR-2015
>             Project: Apache Apex Malhar
>          Issue Type: New Feature
>            Reporter: Pradeep A Dalvi
>
> Projection Operator will allow apex users to project (select/drop) certain fields from
the incoming tuples. This operation might be done unconditionally or based on certain condition.
> Use case:
> -------------
> Not all fields of tuples are of interest for the downstream operators. In such cases,
one may want project selective fields to downstream. Also one may want to drop few fields,
instead of selecting many.
> In certain scenarios, one may want to project certain fields based on given condition
or expression.
> Functionality:
> -----------------
> 1. Projection operator shall receive POJO as input tuple and emit 2 POJOs on separate
output ports i.e. selected and dropped. Selected output port shall emit POJO with selected
fields and dropped output shall emit POJO of dropped fields.
> 2. Operator needs select or drop fields as input params. This shall be specified using
comma separated list of fields.
> 3. Operator shall emit POJO only on connected output ports. In another words, if dropped
output port is not connected, it shall not even try to generate POJOs with dropped fields.



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