Dennis Gove created SOLR-7707:
---------------------------------
Summary: 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
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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