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https://issues.apache.org/jira/browse/SOLR-8185?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dennis Gove updated SOLR-8185:
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Attachment: SOLR-8185.patch
Full patch. All tests pass.
> Add operations support to streaming metrics
> -------------------------------------------
>
> Key: SOLR-8185
> URL: https://issues.apache.org/jira/browse/SOLR-8185
> Project: Solr
> Issue Type: Improvement
> Components: SolrJ
> Reporter: Dennis Gove
> Priority: Minor
> Attachments: SOLR-8185.patch
>
>
> Adds support for operations on stream metrics.
> With this feature one can modify tuple values before applying to the computed
> metric. There are a lot of use-cases I can see with this - I'll describe one
> here.
> Imagine you have a RollupStream which is computing the average over some
> field but you cannot be sure that all documents have a value for that field,
> ie the value is null. When the value is null you want to treat it as a 0.
> With this feature you can accomplish that like this
> {code}
> rollup(
> search(collection1, q=*:*, fl=\"a_s,a_i,a_f\", sort=\"a_s asc\"),
> over=\"a_s\",
> avg(a_i, replace(null, withValue=0)),
> count(*),
> )
> {code}
> The operations are applied to the tuple for each metric in the stream which
> means you perform different operations on different metrics without being
> impacted by operations on other metrics.
> Adding to our previous example, imagine you want to also get the min of a
> field but do not consider null values.
> {code}
> rollup(
> search(collection1, q=*:*, fl=\"a_s,a_i,a_f\", sort=\"a_s asc\"),
> over=\"a_s\",
> avg(a_i, replace(null, withValue=0)),
> min(a_i),
> count(*),
> )
> {code}
> Also, the tuple is not modified for streams that might wrap this one. Ie, the
> only thing that sees the applied operation is that particular metric. If you
> want to apply operations for wrapping streams you can still achieve that with
> the SelectStream (SOLR-7669).
> One feature I'm investigating but this patch DOES NOT add is the ability to
> assign names to the resulting metric value. For example, to allow for
> something like this
> {code}
> rollup(
> search(collection1, q=*:*, fl=\"a_s,a_i,a_f\", sort=\"a_s asc\"),
> over=\"a_s\",
> avg(a_i, replace(null, withValue=0), as="avg_a_i_null_as_0"),
> avg(a_i),
> count(*, as="totalCount"),
> )
> {code}
> Right now that isn't possible because the identifier for each metric would be
> the same "avg_a_i" and as such both couldn't be returned. It's relatively
> easy to add but I have to investigate its impact on the SQL and FacetStream
> areas.
> Depends on SOLR-7669 (SelectStream)
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