[LUCY-113] ORMatcher and ORScorer

• Type: New Feature
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Component/s: Search
• Assignee: Marvin Humphrey
• Reporter: Marvin Humphrey
• Created: 18/Jun/10 03:57
• Updated: 19/Jun/10 00:40
• Resolved: 19/Jun/10 00:40

Description

ORMatcher and and its scoring companion ORScorer are based on Lucene's
DisjunctionSumScorer. They use a priority queue to channel sub-matchers and
proceed doc-at-a-time.

This priority queue is a serious search-time bottlneck and a lot of work has
gone into optimizing the algorithm. As in Lucene, we have inlined the
priority queue and removed as much indirection and function-call overhead as
possible. However, in Lucene, ScorerDocQueue is a separate class, while here
everything is achieved with static functions so that the C compiler may make
maximum optimizations.

ORMatcher is separated from ORScorer as an optimization; during Next(),
ORScorer accumulates scores from subscorers which match, while ORMatcher's
Next() method skips this work and avoids the overhead.