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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (NIFI-2735) Add processor to perform simple aggregations
Date Tue, 06 Sep 2016 19:12:20 GMT

    [ https://issues.apache.org/jira/browse/NIFI-2735?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15468258#comment-15468258
] 

ASF GitHub Bot commented on NIFI-2735:
--------------------------------------

Github user olegz commented on the issue:

    https://github.com/apache/nifi/pull/988
  
    Reviewing. . .


> Add processor to perform simple aggregations
> --------------------------------------------
>
>                 Key: NIFI-2735
>                 URL: https://issues.apache.org/jira/browse/NIFI-2735
>             Project: Apache NiFi
>          Issue Type: New Feature
>          Components: Extensions
>            Reporter: Matt Burgess
>            Assignee: Matt Burgess
>
> This is a proposal for a new processor (AggregateValues, for example) that can perform
simple aggregation operations such as count, sum, average, min, max, and concatenate, over
a set of "related" flow files. For example, when a JSON file is split on an array (using the
SplitJson processor), the total count of the splits, the index of each split, and the unique
indentifier (shared by each split) are stored as attributes in each flow file sent to the
"splits" relationship:
> https://nifi.apache.org/docs/nifi-docs/components/org.apache.nifi.processors.standard.SplitJson/index.html
> These attributes are the "fragment.*" attributes in the documentation for SplitText,
SplitXml, and SplitJson, for example.
> Such a processor could perform these operations for each flow file split from the original
document, and when all documents from a split have been processed, a flow file could be transferred
to an "aggregate" relationship containing attributes for the operation, aggregate value, etc.
> An interesting application of this (besides the actual aggregation operations) is that
you can use the "aggregate" relationship as an event trigger. For example if you need to wait
until all files from a group are processed, you can use AggregateValues and the "aggregate"
relationship to indicate downstream that the entire group has been processed. If there is
not a Split processor upstream, then the attributes (fragment.*) would have to be manipulated
by the data flow designer, but this can be accomplished with other processors (including the
scripting processors if necessary). 



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