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java.lang.Object org.apache.lucene.search.Query org.apache.lucene.search.MultiTermQuery
public abstract class MultiTermQuery
An abstract Query
that matches documents
containing a subset of terms provided by a FilteredTermEnum
enumeration.
This query cannot be used directly; you must subclass
it and define getEnum(org.apache.lucene.index.IndexReader)
to provide a FilteredTermEnum
that iterates through the terms to be
matched.
NOTE: if setRewriteMethod(org.apache.lucene.search.MultiTermQuery.RewriteMethod)
is either
CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE
or SCORING_BOOLEAN_QUERY_REWRITE
, you may encounter a
BooleanQuery.TooManyClauses
exception during
searching, which happens when the number of terms to be
searched exceeds BooleanQuery.getMaxClauseCount()
. Setting setRewriteMethod(org.apache.lucene.search.MultiTermQuery.RewriteMethod)
to CONSTANT_SCORE_FILTER_REWRITE
prevents this.
The recommended rewrite method is CONSTANT_SCORE_AUTO_REWRITE_DEFAULT
: it doesn't spend CPU
computing unhelpful scores, and it tries to pick the most
performant rewrite method given the query.
Note that QueryParser
produces
MultiTermQueries using CONSTANT_SCORE_AUTO_REWRITE_DEFAULT
by default.
Nested Class Summary | |
---|---|
static class |
MultiTermQuery.ConstantScoreAutoRewrite
A rewrite method that tries to pick the best constant-score rewrite method based on term and document counts from the query. |
static class |
MultiTermQuery.RewriteMethod
Abstract class that defines how the query is rewritten. |
Constructor Summary | |
---|---|
MultiTermQuery()
Constructs a query matching terms that cannot be represented with a single Term. |
|
MultiTermQuery(Term term)
Deprecated. check sub class for possible term access - the Term does not make sense for all MultiTermQuerys and will be removed. |
Method Summary | |
---|---|
void |
clearTotalNumberOfTerms()
Expert: Resets the counting of unique terms. |
boolean |
equals(Object obj)
|
protected abstract FilteredTermEnum |
getEnum(IndexReader reader)
Construct the enumeration to be used, expanding the pattern term. |
MultiTermQuery.RewriteMethod |
getRewriteMethod()
|
Term |
getTerm()
Deprecated. check sub class for possible term access - getTerm does not make sense for all MultiTermQuerys and will be removed. |
int |
getTotalNumberOfTerms()
Expert: Return the number of unique terms visited during execution of the query. |
int |
hashCode()
|
protected void |
incTotalNumberOfTerms(int inc)
|
Query |
rewrite(IndexReader reader)
Expert: called to re-write queries into primitive queries. |
void |
setRewriteMethod(MultiTermQuery.RewriteMethod method)
Sets the rewrite method to be used when executing the query. |
String |
toString(String field)
Prints a query to a string, with field assumed to be the
default field and omitted. |
Methods inherited from class org.apache.lucene.search.Query |
---|
clone, combine, createWeight, extractTerms, getBoost, getSimilarity, mergeBooleanQueries, setBoost, toString, weight |
Methods inherited from class java.lang.Object |
---|
finalize, getClass, notify, notifyAll, wait, wait, wait |
Field Detail |
---|
protected Term term
protected MultiTermQuery.RewriteMethod rewriteMethod
public static final MultiTermQuery.RewriteMethod CONSTANT_SCORE_FILTER_REWRITE
This method is faster than the BooleanQuery
rewrite methods when the number of matched terms or
matched documents is non-trivial. Also, it will never
hit an errant BooleanQuery.TooManyClauses
exception.
setRewriteMethod(org.apache.lucene.search.MultiTermQuery.RewriteMethod)
public static final MultiTermQuery.RewriteMethod SCORING_BOOLEAN_QUERY_REWRITE
BooleanClause.Occur.SHOULD
clause in a
BooleanQuery, and keeps the scores as computed by the
query. Note that typically such scores are
meaningless to the user, and require non-trivial CPU
to compute, so it's almost always better to use CONSTANT_SCORE_AUTO_REWRITE_DEFAULT
instead.
NOTE: This rewrite method will hit BooleanQuery.TooManyClauses
if the number of terms
exceeds BooleanQuery.getMaxClauseCount()
.
setRewriteMethod(org.apache.lucene.search.MultiTermQuery.RewriteMethod)
public static final MultiTermQuery.RewriteMethod CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE
SCORING_BOOLEAN_QUERY_REWRITE
except
scores are not computed. Instead, each matching
document receives a constant score equal to the
query's boost.
NOTE: This rewrite method will hit BooleanQuery.TooManyClauses
if the number of terms
exceeds BooleanQuery.getMaxClauseCount()
.
setRewriteMethod(org.apache.lucene.search.MultiTermQuery.RewriteMethod)
public static final MultiTermQuery.RewriteMethod CONSTANT_SCORE_AUTO_REWRITE_DEFAULT
MultiTermQuery.ConstantScoreAutoRewrite
, with MultiTermQuery.ConstantScoreAutoRewrite.setTermCountCutoff(int)
set to
MultiTermQuery.ConstantScoreAutoRewrite.DEFAULT_TERM_COUNT_CUTOFF
and MultiTermQuery.ConstantScoreAutoRewrite.setDocCountPercent(double)
set to
MultiTermQuery.ConstantScoreAutoRewrite.DEFAULT_DOC_COUNT_PERCENT
.
Note that you cannot alter the configuration of this
instance; you'll need to create a private instance
instead.
Constructor Detail |
---|
public MultiTermQuery(Term term)
term
.
public MultiTermQuery()
Method Detail |
---|
public Term getTerm()
protected abstract FilteredTermEnum getEnum(IndexReader reader) throws IOException
IOException
public int getTotalNumberOfTerms()
This method is not thread safe, be sure to only call it when no query is running!
If you re-use the same query instance for another
search, be sure to first reset the term counter
with clearTotalNumberOfTerms()
.
On optimized indexes / no MultiReaders, you get the correct number of unique terms for the whole index. Use this number to compare different queries. For non-optimized indexes this number can also be achieved in non-constant-score mode. In constant-score mode you get the total number of terms seeked for all segments / sub-readers.
clearTotalNumberOfTerms()
public void clearTotalNumberOfTerms()
getTotalNumberOfTerms()
protected void incTotalNumberOfTerms(int inc)
public Query rewrite(IndexReader reader) throws IOException
Query
rewrite
in class Query
IOException
public String toString(String field)
Query
field
assumed to be the
default field and omitted.
The representation used is one that is supposed to be readable
by QueryParser
. However,
there are the following limitations:
toString
in class Query
public MultiTermQuery.RewriteMethod getRewriteMethod()
setRewriteMethod(org.apache.lucene.search.MultiTermQuery.RewriteMethod)
public void setRewriteMethod(MultiTermQuery.RewriteMethod method)
MultiTermQuery.RewriteMethod
.
public int hashCode()
hashCode
in class Query
public boolean equals(Object obj)
equals
in class Query
|
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