[jira] [Commented] (SOLR-8337) Add ReduceOperation and wire it into the ReducerStream

["ASF subversion and git services (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-8337?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15052041#comment-15052041 ] 

ASF subversion and git services commented on SOLR-8337:
-------------------------------------------------------

Commit 1719246 from [~joel.bernstein] in branch 'dev/trunk'
[ https://svn.apache.org/r1719246 ]

SOLR-8337: Add ReduceOperation and wire it into the ReducerStream

> Add ReduceOperation and wire it into the ReducerStream
> ------------------------------------------------------
>
>                 Key: SOLR-8337
>                 URL: https://issues.apache.org/jira/browse/SOLR-8337
>             Project: Solr
>          Issue Type: Bug
>            Reporter: Joel Bernstein
>         Attachments: SOLR-8337.patch, SOLR-8337.patch, SOLR-8337.patch, SOLR-8337.patch, SOLR-8337.patch
>
>
> The current ReducerStream groups all documents that share the same key(s) into a list and emits a single Tuple that contains this list. There is no way to tell the ReducerStream to do something more interesting with groups, for example summing a column within a group, or joining tuples. 
> This ticket adds a new type of operation called a ReduceOperation which is passed to the ReducerStream so that the reduce behavior can be specialized.
> The ReduceOperation has two methods:
> 1) operate(Tuple) : This is called once for each Tuple in a group. This method can be used to aggregate Tuples as they added to a group. 
> 2) reduce() : This is called when the group keys change. This method returns a single Tuple which is output by the ReducerStream. The ReduceOperation must clear it's internal structures when reduce is called as well, to prepare for the next group.



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