Zach Chen created LUCENE-10236:
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Summary: CombinedFieldsQuery to use fieldAndWeights.values() when
constructing MultiNormsLeafSimScorer for scoring
Key: LUCENE-10236
URL: https://issues.apache.org/jira/browse/LUCENE-10236
Project: Lucene - Core
Issue Type: Improvement
Components: modules/sandbox
Reporter: Zach Chen
Assignee: Zach Chen
This is a spin-off issue from discussion in
[https://github.com/apache/lucene/pull/418#issuecomment-967790816], for a quick
fix in CombinedFieldsQuery scoring.
Currently CombinedFieldsQuery would use a constructed
[fields|https://github.com/apache/lucene/blob/3b914a4d73eea8923f823cbdb869de39213411dd/lucene/sandbox/src/java/org/apache/lucene/sandbox/search/CombinedFieldQuery.java#L420-L421]
object to create a MultiNormsLeafSimScorer for scoring, but the fields object
may contain duplicated field-weight pairs as it is [built from looping over
fieldTerms|https://github.com/apache/lucene/blob/3b914a4d73eea8923f823cbdb869de39213411dd/lucene/sandbox/src/java/org/apache/lucene/sandbox/search/CombinedFieldQuery.java#L404-L414],
resulting into duplicated norms being added during scoring calculation in
MultiNormsLeafSimScorer.
E.g. for CombinedFieldsQuery with two fields and two values matching a
particular doc:
{code:java}
CombinedFieldQuery query =
new CombinedFieldQuery.Builder()
.addField("field1", (float) 1.0)
.addField("field2", (float) 1.0)
.addTerm(new BytesRef("foo"))
.addTerm(new BytesRef("zoo"))
.build(); {code}
I would imagine the scoring to be based on the following:
# Sum of freqs on doc = freq(field1:foo) + freq(field2:foo) + freq(field1:zoo)
+ freq(field2:zoo)
# Sum of norms on doc = norm(field1) + norm(field2)
but the current logic would use the following for scoring:
# Sum of freqs on doc = freq(field1:foo) + freq(field2:foo) + freq(field1:zoo)
+ freq(field2:zoo)
# Sum of norms on doc = norm(field1) + norm(field2) + norm(field1) +
norm(field2)
In addition, this differs from how MultiNormsLeafSimScorer is constructed from
CombinedFieldsQuery explain function, which [uses
fieldAndWeights.values()|https://github.com/apache/lucene/blob/3b914a4d73eea8923f823cbdb869de39213411dd/lucene/sandbox/src/java/org/apache/lucene/sandbox/search/CombinedFieldQuery.java#L387-L389]
and does not contain duplicated field-weight pairs.
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