[jira] [Created] (NIFI-2735) Add processor to perform simple aggregations

["Matt Burgess (JIRA)" <ji...@apache.org>]

Matt Burgess created NIFI-2735:
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             Summary: 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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