Adrien Grand created LUCENE-8405:
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Summary: Remove TopHits.maxScore
Key: LUCENE-8405
URL: https://issues.apache.org/jira/browse/LUCENE-8405
Project: Lucene - Core
Issue Type: Task
Reporter: Adrien Grand
Fix For: master (8.0)
I would like to propose removing TopDocs.maxScore. The reasoning is that either
you are sorting by score and then its value is easy to access via the score of
the best hit. Or you sort by one or more fields and computing it is wasteful:
- term frequencies and norms need to be read and decoded for every match
- scores need to be computed on every match
- early-termination optimizations are disabled
It would be more efficient to collect hits twice: once with scores disabled to
get the top hits, and once to get the best score which would run efficiently
thanks to impacts and MAXSCORE, especially with a size of 1:
{code:java}
TopDocs topHits = searcher.search(query, 1);
float maxScore = topHits.scoreDocs.length == 0 ? Float.NaN :
topHits.scoreDocs[0].score;
{code}
The {{doDocScores}} option of TopFieldCollector has drawbacks as well but at
least doesn't disable early-termination optimizations and doesn't require
scores to be computed on every hit.
As this would be a significant breaking change, I'm targeting 8.0.
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