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https://issues.apache.org/jira/browse/SOLR-7707?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14612814#comment-14612814
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Dennis Gove commented on SOLR-7707:
-----------------------------------
Looks like I cut my branch from trunk before those changes were committed. I'll
go through some rebasing tomorrow and post up a new patch. Sorry abut that.
> 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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