mirror of https://github.com/apache/lucene.git
clarify constantScoreRewrite for MultiTermQuery/RangeQuery
git-svn-id: https://svn.apache.org/repos/asf/lucene/java/trunk@776805 13f79535-47bb-0310-9956-ffa450edef68
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@ -22,21 +22,29 @@ import java.io.IOException;
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import org.apache.lucene.index.IndexReader;
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import org.apache.lucene.index.Term;
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import org.apache.lucene.util.ToStringUtils;
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import org.apache.lucene.queryParser.QueryParser; // for javadoc
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/**
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* A {@link Query} that matches documents containing a subset of terms provided
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* by a {@link FilteredTermEnum} enumeration.
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* <P>
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* <code>MultiTermQuery</code> is not designed to be used by itself. <BR>
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* The reason being that it is not intialized with a {@link FilteredTermEnum}
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* enumeration. A {@link FilteredTermEnum} enumeration needs to be provided.
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* <P>
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* For example, {@link WildcardQuery} and {@link FuzzyQuery} extend
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* <code>MultiTermQuery</code> to provide {@link WildcardTermEnum} and
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* {@link FuzzyTermEnum}, respectively.
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* An abstract {@link Query} that matches documents
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* containing a subset of terms provided by a {@link
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* FilteredTermEnum} enumeration.
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*
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* The pattern Term may be null. A query that uses a null pattern Term should
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* override equals and hashcode.
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* <p>This query cannot be used directly; you must subclass
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* it and define {@link #getEnum} to provide a {@link
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* FilteredTermEnum} that iterates through the terms to be
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* matched.
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*
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* <p><b>NOTE</b>: if {@link #setConstantScoreRewrite} is
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* false, you may encounter a {@link
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* BooleanQuery.TooManyClauses} exception during searching,
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* which happens when the number of terms to be searched
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* exceeds {@link BooleanQuery#getMaxClauseCount()}.
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* Setting {@link #setConstantScoreRewrite} to false
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* prevents this.
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*
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* Note that {@link QueryParser} by default produces
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* MultiTermQueries with {@link #setConstantScoreRewrite}
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* true.
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*/
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public abstract class MultiTermQuery extends Query {
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/* @deprecated move to sub class */
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@ -146,10 +154,33 @@ public abstract class MultiTermQuery extends Query {
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return buffer.toString();
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}
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/**
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* @see #setConstantScoreRewrite
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*/
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public boolean getConstantScoreRewrite() {
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return constantScoreRewrite;
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}
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/**
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* This method determines what method is used during searching:
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* <ul>
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*
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* <li> When constantScoreRewrite is <code>false</code>
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* (the default), the query is rewritten to {@link
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* BooleanQuery} with one clause for each term in the
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* range. If the the number of terms in the range
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* exceeds {@link BooleanQuery#getMaxClauseCount()}, a
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* {@link BooleanQuery.TooManyClauses} exception will be
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* thrown during searching. This mode may also give
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* worse performance when the number of terms is large,
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* and/or the number of matching documents is large.
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*
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* <li> When constantScoreRewrite is <code>true</code>,
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* the query is first rewritten to a filter. Matching
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* documents will identical scores, equal to this
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* query's boost.
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* </ul>
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*/
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public void setConstantScoreRewrite(boolean constantScoreRewrite) {
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this.constantScoreRewrite = constantScoreRewrite;
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}
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@ -24,19 +24,12 @@ import org.apache.lucene.index.Term;
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import org.apache.lucene.index.IndexReader;
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/**
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* A Query that matches documents within an exclusive range. A RangeQuery
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* is built by QueryParser for input like <code>[010 TO 120]</code> but only if the QueryParser has
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* the useOldRangeQuery property set to true. The QueryParser default behaviour is to use
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* the newer ConstantScore mode. This is generally preferable because:
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* <ul>
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* <li>In certain situations, it may be faster than the standard RangeQuery mode</li>
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* <li>Unlike the RangeQuery mode, it does not cause a BooleanQuery.TooManyClauses exception if the range of values is large</li>
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* <li>Unlike the RangeQuery mode, it does not influence scoring based on the scarcity of individual terms that may match</li>
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* </ul>
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* A Query that matches documents within an exclusive range.
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*
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*
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* @version $Id$
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* See {@link MultiTermQuery#setConstantScoreRewrite} for the tradeoffs between
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* enabling and disabling constantScoreRewrite mode.
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*/
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public class RangeQuery extends MultiTermQuery {
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private Term lowerTerm;
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private Term upperTerm;
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