[jira] [Resolved] (LUCENE-8020) Don't force sim to score bogus terms (e.g. docfreq=0)

["Robert Muir (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/LUCENE-8020?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Robert Muir resolved LUCENE-8020.
---------------------------------
    Resolution: Fixed

I spun off LUCENE-8023 and LUCENE-8024 to simplify sim impls.

> Don't force sim to score bogus terms (e.g. docfreq=0)
> -----------------------------------------------------
>
>                 Key: LUCENE-8020
>                 URL: https://issues.apache.org/jira/browse/LUCENE-8020
>             Project: Lucene - Core
>          Issue Type: Bug
>            Reporter: Robert Muir
>         Attachments: LUCENE-8020.patch, LUCENE-8020.patch, LUCENE-8020.patch
>
>
> Today all sim formulas have to be "hacked" to deal with the fact that they may be passed stats such as docFreq=0, totalTermFreq=0. This happens easily with spans and there is even a dedicated test for it. All formulas have hacks such as what you see in https://issues.apache.org/jira/browse/LUCENE-6818:
> Instead of:
> {code}
> expected = stats.getTotalTermFreq() * docLen / stats.getNumberOfFieldTokens();
> {code}
> they must do tricks such as:
> {code}
> expected = (1 + stats.getTotalTermFreq()) * docLen / (1 + stats.getNumberOfFieldTokens());
> {code}
> There is no good reason for this, it is just sloppiness in the Query/Weight/Scorer api. I think formulas should work unmodified, we shouldn't pass terms that dont exist or bogus statistics.
> It adds a lot of complexity to the scoring api and makes it difficult to have meaningful/useful explanations, to debug problems, etc. It also makes it really hard to add a new sim.



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