[LUCENE-6184] BooleanScorer should better deal with sparse clauses

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 5.1, 6.0
• Lucene Fields: New
• Assignee: Adrien Grand
• Reporter: Adrien Grand
• Created: 15/Jan/15 15:07
• Updated: 28/Aug/22 14:23
• Resolved: 19/Jan/15 14:58

Description

The way that BooleanScorer works looks like this:

for each (window of 2048 docs) {
  for each (optional scorer) {
    scorer.score(window)
  }
}

This is not efficient for very sparse clauses (doc freq much lower than maxDoc/2048) since we keep on scoring windows of documents that do not match anything. BooleanScorer2 currently performs better in those cases.