nl.inl.blacklab.search.lucene

Class BLSpans

java.lang.Object

org.apache.lucene.search.DocIdSetIterator

org.apache.lucene.search.spans.Spans

nl.inl.blacklab.search.lucene.BLSpans

Direct Known Subclasses:

BLSpansWrapper, MockSpans, SpansConstrained

public abstract class BLSpans
extends org.apache.lucene.search.spans.Spans

Will be the base class for all our own Spans classes. Is able to give extra guarantees about the hits in this Spans object, such as if every hit is equal in length, if there may be duplicates, etc. This information will help us optimize certain operations, such as sequence queries, in certain cases. The default implementation is appropriate for Spans classes that return only single-term hits.

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	childClausesCaptureGroups Should we ask our clauses for captured groups? If the clauses don't capture any groups, this will be set to false to improve performance.
static int	MAX_UNLIMITED

Fields inherited from class org.apache.lucene.search.spans.Spans

NO_MORE_POSITIONS

Fields inherited from class org.apache.lucene.search.DocIdSetIterator

NO_MORE_DOCS

Constructor Summary

Constructors

Constructor and Description
BLSpans()

Method Summary

Modifier and Type	Method and Description
int	advanceStartPosition(int target) Advance the start position in the current doc to target or beyond.
long	cost()
abstract void	getCapturedGroups(Span[] capturedGroups) Get the start and end position for the captured groups contained in this BLSpans (sub)tree.
static BLSpans	optSortUniq(BLSpans spans, boolean sort, boolean removeDuplicates)
protected abstract void	passHitQueryContextToClauses(HitQueryContext context) Called by setHitQueryContext() to pass the context to child clauses.
void	setHitQueryContext(HitQueryContext context) Give the BLSpans tree a way to access captured groups, and the capture groups themselves a way to register themselves..

Methods inherited from class org.apache.lucene.search.spans.Spans

asTwoPhaseIterator, collect, doCurrentSpans, doStartCurrentDoc, endPosition, nextStartPosition, positionsCost, startPosition, toString, width

Methods inherited from class org.apache.lucene.search.DocIdSetIterator

advance, all, docID, empty, nextDoc, slowAdvance

Methods inherited from class java.lang.Object

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

Field Detail

MAX_UNLIMITED

public static final int MAX_UNLIMITED

See Also:

Constant Field Values

childClausesCaptureGroups

protected boolean childClausesCaptureGroups

Should we ask our clauses for captured groups? If the clauses don't capture any groups, this will be set to false to improve performance.

Constructor Detail

BLSpans

public BLSpans()

Method Detail

setHitQueryContext

public void setHitQueryContext(HitQueryContext context)

Give the BLSpans tree a way to access captured groups, and the capture groups themselves a way to register themselves.. subclasses should override this method, pass the context to their child clauses (if any), and either: - register the captured group they represent with the context (SpansCaptureGroup does this), OR - store the context so they can later use it to access captured groups (SpansBackreference does this)

Parameters:

context - the hit query context, that e.g. keeps track of captured groups

passHitQueryContextToClauses

protected abstract void passHitQueryContextToClauses(HitQueryContext context)

Called by setHitQueryContext() to pass the context to child clauses.

Parameters:

context - the hit query context, that e.g. keeps track of captured groups

getCapturedGroups

public abstract void getCapturedGroups(Span[] capturedGroups)

Get the start and end position for the captured groups contained in this BLSpans (sub)tree.

Parameters:

capturedGroups - an array the size of the total number of groups in the query; the start and end positions for the groups in this subtree will be placed in here.

advanceStartPosition

public int advanceStartPosition(int target)
                         throws IOException

Advance the start position in the current doc to target or beyond. Always at least advances to the next hit, even if the current start position is already at or beyond the target.

Parameters:

target - target start position to advance to

Returns:

new start position, or Spans.NO_MORE_POSITIONS if we're done with this document

Throws:

IOException - on error

cost

public long cost()

Specified by:

cost in class org.apache.lucene.search.DocIdSetIterator

optSortUniq

public static BLSpans optSortUniq(BLSpans spans,
                                  boolean sort,
                                  boolean removeDuplicates)