Optimizations to TopScoreDocCollector and TopFieldCollector
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Key: LUCENE-1593
URL: https://issues.apache.org/jira/browse/LUCENE-1593
Project: Lucene - Java
Issue Type: Improvement
Components: Search
Reporter: Shai Erera
Fix For: 2.9
This is a spin-off of LUCENE-1575 and proposes to optimize TSDC and TFC code to
remove unnecessary checks. The plan is:
# Ensure that IndexSearcher returns segements in increasing doc Id order,
instead of numDocs().
# Change TSDC and TFC's code to not use the doc id as a tie breaker. New docs
will always have larger ids and therefore cannot compete.
# Pre-populate HitQueue with sentinel values in TSDC (score = Float.NEG_INF)
and remove the check if reusableSD == null.
# Also move to use "changing top" and then call adjustTop(), in case we update
the queue.
# some methods in Sort explicitly add SortField.FIELD_DOC as a "tie breaker"
for the last SortField. But, doing so should not be necessary (since we already
break ties by docID), and is in fact less efficient (once the above
optimization is in).
# Investigate PQ - can we deprecate insert() and have only
insertWithOverflow()? Add a addDummyObjects method which will populate the
queue without "arranging" it, just store the objects in the array (this can be
used to pre-populate sentinel values)?
I will post a patch as well as some perf measurements as soon as I have them.
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