This query cannot be used directly; you must subclass + * it and define {@link #getEnum} to provide a {@link + * FilteredTermEnum} that iterates through the terms to be + * matched. + * + *
NOTE: if {@link #setRewriteMethod} is either + * {@link #CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE} or {@link + * #SCORING_BOOLEAN_QUERY_REWRITE}, you may encounter a + * {@link BooleanQuery.TooManyClauses} exception during + * searching, which happens when the number of terms to be + * searched exceeds {@link + * BooleanQuery#getMaxClauseCount()}. Setting {@link + * #setRewriteMethod} to {@link #CONSTANT_SCORE_FILTER_REWRITE} + * prevents this. + * + *
The recommended rewrite method is {@link + * #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. If you + * need scoring (like {@link FuzzyQuery}, use + * {@link TopTermsScoringBooleanQueryRewrite} which uses + * a priority queue to only collect competitive terms + * and not hit this limitation. + * + * Note that {@link QueryParser} produces + * MultiTermQueries using {@link + * #CONSTANT_SCORE_AUTO_REWRITE_DEFAULT} by default. + */ +public abstract class MultiTermQuery extends Query { + protected RewriteMethod rewriteMethod = CONSTANT_SCORE_AUTO_REWRITE_DEFAULT; + transient int numberOfTerms = 0; + + /** Abstract class that defines how the query is rewritten. */ + public static abstract class RewriteMethod implements Serializable { + public abstract Query rewrite(IndexReader reader, MultiTermQuery query) throws IOException; + } + + /** A rewrite method that first creates a private Filter, + * by visiting each term in sequence and marking all docs + * for that term. Matching documents are assigned a + * constant score equal to the query's boost. + * + *
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 {@link BooleanQuery.TooManyClauses}
+ * exception.
+ *
+ * @see #setRewriteMethod */
+ public static final RewriteMethod CONSTANT_SCORE_FILTER_REWRITE = new RewriteMethod() {
+ @Override
+ public Query rewrite(IndexReader reader, MultiTermQuery query) {
+ Query result = new ConstantScoreQuery(new MultiTermQueryWrapperFilter NOTE: This rewrite method will hit {@link
+ * BooleanQuery.TooManyClauses} if the number of terms
+ * exceeds {@link BooleanQuery#getMaxClauseCount}.
+ *
+ * @see #setRewriteMethod */
+ public final static RewriteMethod SCORING_BOOLEAN_QUERY_REWRITE = ScoringRewrite.SCORING_BOOLEAN_QUERY_REWRITE;
+
+ /** Like {@link #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 {@link
+ * BooleanQuery.TooManyClauses} if the number of terms
+ * exceeds {@link BooleanQuery#getMaxClauseCount}.
+ *
+ * @see #setRewriteMethod */
+ public final static RewriteMethod CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE = ScoringRewrite.CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE;
+
+ /**
+ * A rewrite method that first translates each term into
+ * {@link BooleanClause.Occur#SHOULD} clause in a BooleanQuery, and keeps the
+ * scores as computed by the query.
+ *
+ *
+ * This rewrite method only uses the top scoring terms so it will not overflow
+ * the boolean max clause count. It is the default rewrite method for
+ * {@link FuzzyQuery}.
+ *
+ * @see #setRewriteMethod
+ */
+ public static final class TopTermsScoringBooleanQueryRewrite extends TopTermsRewrite
+ * NOTE: if {@link BooleanQuery#getMaxClauseCount} is smaller than
+ *
+ * This rewrite method only uses the top scoring terms so it will not overflow
+ * the boolean max clause count.
+ *
+ * @see #setRewriteMethod
+ */
+ public static final class TopTermsBoostOnlyBooleanQueryRewrite extends TopTermsRewrite
+ * NOTE: if {@link BooleanQuery#getMaxClauseCount} is smaller than
+ * 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 {@link #clearTotalNumberOfTerms}.
+ * On single-segment indexes / no MultiReaders, you get the correct number of
+ * unique terms for the whole index. Use this number to compare different queries.
+ * For multi-segment 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.
+ * @see #clearTotalNumberOfTerms
+ * @deprecated Don't use this method, as its not thread safe and useless.
+ */
+ @Deprecated
+ public int getTotalNumberOfTerms() {
+ return numberOfTerms;
+ }
+
+ /**
+ * Expert: Resets the counting of unique terms.
+ * Do this before executing the query/filter.
+ * @see #getTotalNumberOfTerms
+ * @deprecated Don't use this method, as its not thread safe and useless.
+ */
+ @Deprecated
+ public void clearTotalNumberOfTerms() {
+ numberOfTerms = 0;
+ }
+
+ /**
+ * @deprecated Don't use this method, as its not thread safe and useless.
+ */
+ @Deprecated
+ protected void incTotalNumberOfTerms(int inc) {
+ numberOfTerms += inc;
+ }
+
+ /**
+ * To rewrite to a simpler form, instead return a simpler
+ * enum from {@link #getEnum(IndexReader)}. For example,
+ * to rewrite to a single term, return a {@link SingleTermEnum}
+ */
+ @Override
+ public final Query rewrite(IndexReader reader) throws IOException {
+ return rewriteMethod.rewrite(reader, this);
+ }
+
+ /**
+ * @see #setRewriteMethod
+ */
+ public RewriteMethod getRewriteMethod() {
+ return rewriteMethod;
+ }
+
+ /**
+ * Sets the rewrite method to be used when executing the
+ * query. You can use one of the four core methods, or
+ * implement your own subclass of {@link RewriteMethod}. */
+ public void setRewriteMethod(RewriteMethod method) {
+ rewriteMethod = method;
+ }
+
+ @Override
+ public int hashCode() {
+ final int prime = 31;
+ int result = 1;
+ result = prime * result + Float.floatToIntBits(getBoost());
+ result = prime * result;
+ result += rewriteMethod.hashCode();
+ return result;
+ }
+
+ @Override
+ public boolean equals(Object obj) {
+ if (this == obj)
+ return true;
+ if (obj == null)
+ return false;
+ if (getClass() != obj.getClass())
+ return false;
+ MultiTermQuery other = (MultiTermQuery) obj;
+ if (Float.floatToIntBits(getBoost()) != Float.floatToIntBits(other.getBoost()))
+ return false;
+ if (!rewriteMethod.equals(other.rewriteMethod)) {
+ return false;
+ }
+ return true;
+ }
+
+}
size terms.
+ * size, then it will be used instead.
+ */
+ public TopTermsScoringBooleanQueryRewrite(int size) {
+ super(size);
+ }
+
+ @Override
+ protected int getMaxSize() {
+ return BooleanQuery.getMaxClauseCount();
+ }
+
+ @Override
+ protected BooleanQuery getTopLevelQuery() {
+ return new BooleanQuery(true);
+ }
+
+ @Override
+ protected void addClause(BooleanQuery topLevel, Term term, float boost) {
+ final TermQuery tq = new TermQuery(term);
+ tq.setBoost(boost);
+ topLevel.add(tq, BooleanClause.Occur.SHOULD);
+ }
+ }
+
+ /**
+ * A rewrite method that first translates each term into
+ * {@link BooleanClause.Occur#SHOULD} clause in a BooleanQuery, but the scores
+ * are only computed as the boost.
+ * size terms.
+ * size, then it will be used instead.
+ */
+ public TopTermsBoostOnlyBooleanQueryRewrite(int size) {
+ super(size);
+ }
+
+ @Override
+ protected int getMaxSize() {
+ return BooleanQuery.getMaxClauseCount();
+ }
+
+ @Override
+ protected BooleanQuery getTopLevelQuery() {
+ return new BooleanQuery(true);
+ }
+
+ @Override
+ protected void addClause(BooleanQuery topLevel, Term term, float boost) {
+ final Query q = new ConstantScoreQuery(new TermQuery(term));
+ q.setBoost(boost);
+ topLevel.add(q, BooleanClause.Occur.SHOULD);
+ }
+ }
+
+ /** A rewrite method that tries to pick the best
+ * constant-score rewrite method based on term and
+ * document counts from the query. If both the number of
+ * terms and documents is small enough, then {@link
+ * #CONSTANT_SCORE_BOOLEAN_QUERY_REWRITE} is used.
+ * Otherwise, {@link #CONSTANT_SCORE_FILTER_REWRITE} is
+ * used.
+ */
+ public static class ConstantScoreAutoRewrite extends org.apache.lucene.search.ConstantScoreAutoRewrite {}
+
+ /** Read-only default instance of {@link
+ * ConstantScoreAutoRewrite}, with {@link
+ * ConstantScoreAutoRewrite#setTermCountCutoff} set to
+ * {@link
+ * ConstantScoreAutoRewrite#DEFAULT_TERM_COUNT_CUTOFF}
+ * and {@link
+ * ConstantScoreAutoRewrite#setDocCountPercent} set to
+ * {@link
+ * ConstantScoreAutoRewrite#DEFAULT_DOC_COUNT_PERCENT}.
+ * Note that you cannot alter the configuration of this
+ * instance; you'll need to create a private instance
+ * instead. */
+ public final static RewriteMethod CONSTANT_SCORE_AUTO_REWRITE_DEFAULT = new ConstantScoreAutoRewrite() {
+ @Override
+ public void setTermCountCutoff(int count) {
+ throw new UnsupportedOperationException("Please create a private instance");
+ }
+
+ @Override
+ public void setDocCountPercent(double percent) {
+ throw new UnsupportedOperationException("Please create a private instance");
+ }
+
+ // Make sure we are still a singleton even after deserializing
+ protected Object readResolve() {
+ return CONSTANT_SCORE_AUTO_REWRITE_DEFAULT;
+ }
+ };
+
+ /**
+ * Constructs a query matching terms that cannot be represented with a single
+ * Term.
+ */
+ public MultiTermQuery() {
+ }
+
+ /** Construct the enumeration to be used, expanding the pattern term. */
+ protected abstract FilteredTermEnum getEnum(IndexReader reader)
+ throws IOException;
+
+ /**
+ * Expert: Return the number of unique terms visited during execution of the query.
+ * If there are many of them, you may consider using another query type
+ * or reduce your total term count in index.
+ *