[jira] [Created] (SOLR-16144) Don't internally round [foreground|background]_popularity values in RelatednessAgg

["Michael Gibney (Jira)" <ji...@apache.org>]

Michael Gibney created SOLR-16144:
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             Summary: Don't internally round [foreground|background]_popularity values in RelatednessAgg
                 Key: SOLR-16144
                 URL: https://issues.apache.org/jira/browse/SOLR-16144
             Project: Solr
          Issue Type: Improvement
      Security Level: Public (Default Security Level. Issues are Public)
          Components: Facet Module
    Affects Versions: main (10.0)
            Reporter: Michael Gibney


The "relatedness" facet function supports the concept of {{foreground_popularity}} and {{background_popularity}} -- i.e., the cardinality of the intersection of bucket domain with the foreground and background sets (respectively), each normalized with respect to background set cardinality.

The logic appears to be:
# To provide clients with context of computed relatedness values
# To preemptively (optionally) screen out "noise" from low-frequency terms via the {{min_popularity}} function parameter.

For both purposes, popularity values are currently rounded to 5 digits.

This issue proposes that although rounding to 5 digits makes sense for the _first_ case (providing context to clients), this arbitrary truncation does not make sense as currently implemented for internally evaluating threshold pop values for bucket inclusion.

Consider the case of a high-cardinality field with a relatively large background set and a selective foreground set. For {{|background_set| = 2,000,000}} and a foreground set of cardinality 9, even a bucket with a domain that exactly matches the foreground set would be screened out, for _any_ explicit setting of {{min_popularity}}.

This behavior is due to where the rounding takes place (internally, upon initial {{computeDerivedValues()}}). It is further problematic that {{RelatednessAgg}} will currently accept {{min_popularity < 0.00001}}, which would be guaranteed to exclude _all_ buckets.



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