[jira] [Comment Edited] (SOLR-7707) Add StreamExpression Support to RollupStream

["Joel Bernstein (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-7707?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14613162#comment-14613162 ] 

Joel Bernstein edited comment on SOLR-7707 at 7/3/15 12:37 PM:
---------------------------------------------------------------

No problem, I'm still wrapping up SOLR-7441.


was (Author: joel.bernstein):
No problem, I'm still wrapping up SOLR-744.

> Add StreamExpression Support to RollupStream
> --------------------------------------------
>
>                 Key: SOLR-7707
>                 URL: https://issues.apache.org/jira/browse/SOLR-7707
>             Project: Solr
>          Issue Type: Improvement
>          Components: SolrJ
>            Reporter: Dennis Gove
>            Priority: Minor
>         Attachments: SOLR-7707.patch, SOLR-7707.patch
>
>
> This ticket is to add Stream Expression support to the RollupStream as discussed in SOLR-7560.
> Proposed expression syntax for the RollupStream (copied from that ticket)
> {code}
> rollup(
>   someStream(....),
>   over="fieldA, fieldB, fieldC",
>   min(fieldA),
>   max(fieldA),
>   min(fieldB),
>   mean(fieldD),
>   sum(fieldC)
> )
> {code}
> This requires making the *Metric types Expressible but I think that ends up as a good thing. Would make it real easy to support other options on metrics like excluding outliers, for example find the sum of values within 3 standard deviations from the mean could be 
> {code}
> sum(fieldC, limit=standardDev(3))
> {code}
>  (note, how that particular calculation could be implemented is left as an exercise for the reader, I'm just using it as an example of adding additional options on a relatively simple metric).
> Another option example is what to do with null values. For example, in some cases a null should not impact a mean but in others it should. You could express those as
> {code}
> mean(fieldA, replace(null, 0))  // replace null values with 0 thus leading to an impact on the mean
> mean(fieldA, includeNull="true") // nulls are counted in the denominator but nothing added to numerator
> mean(fieldA, includeNull="false") // nulls neither counted in denominator nor added to numerator
> mean(fieldA, replace(null, fieldB), includeNull="true") // if fieldA is null replace it with fieldB, include null fieldB in mean
> {code}
> so on and so forth.



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