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https://issues.apache.org/jira/browse/SOLR-13025?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jan Høydahl updated SOLR-13025:
-------------------------------
Description:
This is a follow-up of LUCENE-8563: Lucene changed its BM25Similarity
implementation to no longer multiply all scores by (k1 + 1). Solr was left
unchanged by replacing uses of BM25Similarity with LegacyBM25Similarity which
returns the same scores as in 7.x.
This Jira makes the default similarity depend on {{luceneMatchVersion}} for
back-compat if schema either does not define a similarity of defines
{{SchemaSimilarityFactory}}. If a user has explicitly defined
{{BM25SimilarityFactory}} then the new will be used and she will need to
replace with {{LegacyBM25SimilarityFactory}} if she wants to keep old absolute
scores (most often not necessary).
This change is also described in RefGuide and CHANGES.
was:This is a follow-up of LUCENE-8563: Lucene changed its BM25Similarity
implementation to no longer multiply all scores by (k1 + 1). Solr was left
unchanged by replacing uses of BM25Similarity with LegacyBM25Similarity which
returns the same scores as in 7.x. However it would be nice to switch back to
BM25Similarity, either all the time with a note in the migration guide, or
based on the luceneMatchVersion of the collection.
> SchemaSimilarityFactory fallback to LegacyBM25Similarity
> --------------------------------------------------------
>
> Key: SOLR-13025
> URL: https://issues.apache.org/jira/browse/SOLR-13025
> Project: Solr
> Issue Type: Task
> Security Level: Public(Default Security Level. Issues are Public)
> Components: search
> Affects Versions: master (8.0)
> Reporter: Adrien Grand
> Assignee: Jan Høydahl
> Priority: Blocker
> Fix For: master (8.0)
>
>
> This is a follow-up of LUCENE-8563: Lucene changed its BM25Similarity
> implementation to no longer multiply all scores by (k1 + 1). Solr was left
> unchanged by replacing uses of BM25Similarity with LegacyBM25Similarity which
> returns the same scores as in 7.x.
> This Jira makes the default similarity depend on {{luceneMatchVersion}} for
> back-compat if schema either does not define a similarity of defines
> {{SchemaSimilarityFactory}}. If a user has explicitly defined
> {{BM25SimilarityFactory}} then the new will be used and she will need to
> replace with {{LegacyBM25SimilarityFactory}} if she wants to keep old
> absolute scores (most often not necessary).
> This change is also described in RefGuide and CHANGES.
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