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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (APEXMALHAR-2015) Projection Operator
Date Fri, 18 Mar 2016 12:32:33 GMT

    [ https://issues.apache.org/jira/browse/APEXMALHAR-2015?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15201403#comment-15201403

ASF GitHub Bot commented on APEXMALHAR-2015:

Github user yogidevendra commented on a diff in the pull request:

    --- Diff: library/src/test/java/com/datatorrent/lib/projection/DummyProjection.java ---
    @@ -0,0 +1,33 @@
    + * Licensed to the Apache Software Foundation (ASF) under one
    + * or more contributor license agreements.  See the NOTICE file
    + * distributed with this work for additional information
    + * regarding copyright ownership.  The ASF licenses this file
    + * to you under the Apache License, Version 2.0 (the
    + * "License"); you may not use this file except in compliance
    + * with the License.  You may obtain a copy of the License at
    + *
    + *   http://www.apache.org/licenses/LICENSE-2.0
    + *
    + * Unless required by applicable law or agreed to in writing,
    + * software distributed under the License is distributed on an
    + * KIND, either express or implied.  See the License for the
    + * specific language governing permissions and limitations
    + * under the License.
    + */
    +package com.datatorrent.lib.projection;
    +class DummyProjection extends ProjectionOperator
    --- End diff --
    How about having this as inner class instead of separate file?

> 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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