[LUCENE-10469] ConstantScoreQuery doesn't propagate its score mode correctly

• Type: Task
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 9.1
• Lucene Fields: New
• Assignee: Unassigned
• Reporter: Adrien Grand
• Created: 16/Mar/22 11:12
• Updated: 28/Aug/22 16:37
• Resolved: 16/Mar/22 12:20

Description

We just noticed a performance bug on Elasticsearch that if you issue a search request sorted by field and the query is a MatchAllDocsQuery then everything works as expected.

But if you change the query to be a MatchAllDocsQuery within a ConstantScoreQuery then the query suddenly visits all matching documents. This is due to the fact that ConstantScoreQuery always passes COMPLETE_NO_SCORES to the inner weight, and thet the MatchAllDocsQuery's optimized bulk scorer performs a brute-force for-loop over the documents to score unless the score mode is not exhaustive.

The fix consists of making ConstantScoreQuery propagate a non-exhaustive score mode to the inner weight when the score mode that is passed to the ConstantScoreQuery is not exhaustive itself.

Issue Links

• links to: GitHub Pull Request #750