Package org.apache.lucene.search

Class QueryVisitor

java.lang.Object

org.apache.lucene.search.QueryVisitor

public abstract class QueryVisitor
extends Object

Allows recursion through a query tree

See Also:

Query.visit(QueryVisitor)

Field Summary

Fields

Modifier and Type	Field	Description
static QueryVisitor	EMPTY_VISITOR	A QueryVisitor implementation that does nothing

Constructor Summary

Constructors

Constructor	Description
QueryVisitor()

Method Summary

Modifier and Type	Method	Description
boolean	acceptField(String field)	Whether or not terms from this field are of interest to the visitor Implement this to avoid collecting terms from heavy queries such as TermInSetQuery that are not running on fields of interest
void	consumeTerms(Query query, Term... terms)	Called by leaf queries that match on specific terms
QueryVisitor	getSubVisitor(BooleanClause.Occur occur, Query parent)	Pulls a visitor instance for visiting child clauses of a query The default implementation returns this, unless occur is equal to BooleanClause.Occur.MUST_NOT in which case it returns EMPTY_VISITOR
static QueryVisitor	termCollector(Set<Term> termSet)	Builds a QueryVisitor instance that collects all terms that may match a query
void	visitLeaf(Query query)	Called by leaf queries that do not match on terms

Methods inherited from class java.lang.Object

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

Field Detail

EMPTY_VISITOR

public static final QueryVisitor EMPTY_VISITOR

A QueryVisitor implementation that does nothing

Constructor Detail

QueryVisitor

public QueryVisitor()

Method Detail

consumeTerms

public void consumeTerms(Query query,
                         Term... terms)

Called by leaf queries that match on specific terms

Parameters:

query - the leaf query

terms - the terms the query will match on

visitLeaf

public void visitLeaf(Query query)

Called by leaf queries that do not match on terms

Parameters:

query - the query

acceptField

public boolean acceptField(String field)

Whether or not terms from this field are of interest to the visitor Implement this to avoid collecting terms from heavy queries such as TermInSetQuery that are not running on fields of interest

getSubVisitor

public QueryVisitor getSubVisitor(BooleanClause.Occur occur,
                                  Query parent)

Pulls a visitor instance for visiting child clauses of a query The default implementation returns this, unless occur is equal to BooleanClause.Occur.MUST_NOT in which case it returns EMPTY_VISITOR

Parameters:

occur - the relationship between the parent and its children

parent - the query visited

termCollector

public static QueryVisitor termCollector(Set<Term> termSet)

Builds a QueryVisitor instance that collects all terms that may match a query

Parameters:

termSet - a Set to add collected terms to