org.apache.lucene.search

Class FilteredQuery.RandomAccessFilterStrategy

java.lang.Object

org.apache.lucene.search.FilteredQuery.FilterStrategy

org.apache.lucene.search.FilteredQuery.RandomAccessFilterStrategy

Enclosing class:

FilteredQuery

public static class FilteredQuery.RandomAccessFilterStrategy
extends FilteredQuery.FilterStrategy

A FilteredQuery.FilterStrategy that conditionally uses a random access filter if the given DocIdSet supports random access (returns a non-null value from DocIdSet.bits()) and useRandomAccess(Bits, long) returns true. Otherwise this strategy falls back to a "zig-zag join" ( FilteredQuery.LEAP_FROG_FILTER_FIRST_STRATEGY) strategy .

Constructor Summary

Constructors

Constructor and Description
FilteredQuery.RandomAccessFilterStrategy()

Method Summary

Methods

Modifier and Type	Method and Description
Scorer	filteredScorer(LeafReaderContext context, Weight weight, DocIdSet docIdSet) Returns a filtered Scorer based on this strategy.
protected boolean	useRandomAccess(Bits bits, long filterCost) Expert: decides if a filter should be executed as "random-access" or not.

Methods inherited from class org.apache.lucene.search.FilteredQuery.FilterStrategy

filteredBulkScorer

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

FilteredQuery.RandomAccessFilterStrategy

public FilteredQuery.RandomAccessFilterStrategy()

Method Detail

filteredScorer

public Scorer filteredScorer(LeafReaderContext context,
                    Weight weight,
                    DocIdSet docIdSet)
                      throws IOException

Description copied from class: FilteredQuery.FilterStrategy

Returns a filtered Scorer based on this strategy.

Specified by:

filteredScorer in class FilteredQuery.FilterStrategy

Parameters:

context - the LeafReaderContext for which to return the Scorer.

weight - the FilteredQuery Weight to create the filtered scorer.

docIdSet - the filter DocIdSet to apply

Returns:

a filtered scorer

Throws:

IOException - if an IOException occurs

useRandomAccess

protected boolean useRandomAccess(Bits bits,
                      long filterCost)

Expert: decides if a filter should be executed as "random-access" or not. random-access means the filter "filters" in a similar way as deleted docs are filtered in Lucene. This is faster when the filter accepts many documents. However, when the filter is very sparse, it can be faster to execute the query+filter as a conjunction in some cases. The default implementation returns true if the filter matches more than 1% of documents

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.