[jira] [Resolved] (LUCENE-8025) compute avgdl correctly for DOCS_ONLY

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

     [ https://issues.apache.org/jira/browse/LUCENE-8025?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Robert Muir resolved LUCENE-8025.
---------------------------------
       Resolution: Fixed
    Fix Version/s: 7.2
                   master (8.0)

> compute avgdl correctly for DOCS_ONLY
> -------------------------------------
>
>                 Key: LUCENE-8025
>                 URL: https://issues.apache.org/jira/browse/LUCENE-8025
>             Project: Lucene - Core
>          Issue Type: Bug
>            Reporter: Robert Muir
>            Priority: Major
>             Fix For: master (8.0), 7.2
>
>         Attachments: LUCENE-8025.patch
>
>
> Spinoff of LUCENE-8007:
> If you omit term frequencies, we should score as if all tf values were 1. This is the way it worked for e.g. ClassicSimilarity and you can understand how it degrades. 
> However for sims such as BM25, we bail out on computing avg doclength (and just return a bogus value of 1) today, screwing up stuff related to length normalization too, which is separate.
> Instead of a bogus value, we should substitute sumDocFreq for sumTotalTermFreq (all postings have freq of 1, since you omitted them).



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