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https://issues.apache.org/jira/browse/LUCENE-9269?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17055927#comment-17055927
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Michele Palmia edited comment on LUCENE-9269 at 3/10/20, 1:15 PM:
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I was actually just looking at a [user
report|https://mail-archives.apache.org/mod_mbox/lucene-dev/202003.mbox/%3CCALyzSEn%2BQFoT3MpNYkxw-dEK9jc59mSTvXqccuUVMMDAgOMMmA%40mail.gmail.com%3E]
that came to lucene-dev and looked interesting. In their use case, they were
using fuzzy queries, that in turn generate blended queries that are affected by
this issue. Maybe users of BlendedQuery/FuzzyQuery should be able to find some
form of warning in the docs (while
[LUCENE-8840|https://issues.apache.org/jira/browse/LUCENE-8840] is not fixed)?
was (Author: micpalmia):
I was actually just looking at a [user
report|https://mail-archives.apache.org/mod_mbox/lucene-dev/202003.mbox/%3CCALyzSEn%2BQFoT3MpNYkxw-dEK9jc59mSTvXqccuUVMMDAgOMMmA%40mail.gmail.com%3E]
that came to lucene-dev and looked interesting. In their use case, they were
using fuzzy queries, that in turn generate blended queries that are affected by
this issue. Maybe users of BlendedQuery/FuzzyQuery should be able to find some
form of warning in the docs?
> Blended queries with boolean rewrite can result in inconstitent scores
> ----------------------------------------------------------------------
>
> Key: LUCENE-9269
> URL: https://issues.apache.org/jira/browse/LUCENE-9269
> Project: Lucene - Core
> Issue Type: Bug
> Components: core/search
> Affects Versions: 8.4
> Reporter: Michele Palmia
> Priority: Minor
> Attachments: LUCENE-9269-test.patch
>
>
> If two blended queries are should clauses of a boolean query and are built so
> that
> * some of their terms are the same
> * their rewrite method is BlendedTermQuery.BOOLEAN_REWRITE
> the docFreq for the overlapping terms used for scoring is picked as follow:
> # if the overlapping terms are not boosted, the df of the term in the first
> blended query is used
> # if any of the overlapping terms is boosted, the df is picked at (what
> looks like) random.
> A few examples using a field with 2 terms: f:a (df: 2), and f:b (df: 3).
> {code:java}
> a)
> Blended(f:a f:b) Blended (f:a)
> df: 3 df: 2
> gets rewritten to:
> (f:a)^2.0 (f:b)
> df: 3 df:2
> b)
> Blended(f:a) Blended(f:a f:b)
> df: 2 df: 3
> gets rewritten to:
> (f:a)^2.0 (f:b)
> df: 2 df:2
> c)
> Blended(f:a f:b^0.66) Blended (f:a^0.75)
> df: 3 df: 2
> gets rewritten to:
> (f:a)^1.75 (f:b)^0.66
> df:? df:2
> {code}
> with ? either 2 or 3, depending on the run.
>
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