Warning: this query is not very scalable with its default prefix - * length of 0 - in this case, *every* term will be enumerated and - * cause an edit score calculation. - * - *
This query uses {@link MultiTermQuery.TopTermsScoringBooleanQueryRewrite}
- * as default. So terms will be collected and scored according to their
- * edit distance. Only the top terms are used for building the {@link BooleanQuery}.
- * It is not recommended to change the rewrite mode for fuzzy queries.
- */
-public class FuzzyQuery extends MultiTermQuery {
-
- public final static float defaultMinSimilarity = 0.5f;
- public final static int defaultPrefixLength = 0;
- public final static int defaultMaxExpansions = Integer.MAX_VALUE;
-
- private float minimumSimilarity;
- private int prefixLength;
- private boolean termLongEnough = false;
-
- protected Term term;
-
- /**
- * Create a new FuzzyQuery that will match terms with a similarity
- * of at least minimumSimilarity to term.
- * If a prefixLength > 0 is specified, a common prefix
- * of that length is also required.
- *
- * @param term the term to search for
- * @param minimumSimilarity a value between 0 and 1 to set the required similarity
- * between the query term and the matching terms. For example, for a
- * minimumSimilarity of 0.5 a term of the same length
- * as the query term is considered similar to the query term if the edit distance
- * between both terms is less than length(term)*0.5
- * @param prefixLength length of common (non-fuzzy) prefix
- * @param maxExpansions the maximum number of terms to match. If this number is
- * greater than {@link BooleanQuery#getMaxClauseCount} when the query is rewritten,
- * then the maxClauseCount will be used instead.
- * @throws IllegalArgumentException if minimumSimilarity is >= 1 or < 0
- * or if prefixLength < 0
- */
- public FuzzyQuery(Term term, float minimumSimilarity, int prefixLength,
- int maxExpansions) {
- this.term = term;
-
- if (minimumSimilarity >= 1.0f)
- throw new IllegalArgumentException("minimumSimilarity >= 1");
- else if (minimumSimilarity < 0.0f)
- throw new IllegalArgumentException("minimumSimilarity < 0");
- if (prefixLength < 0)
- throw new IllegalArgumentException("prefixLength < 0");
- if (maxExpansions < 0)
- throw new IllegalArgumentException("maxExpansions < 0");
-
- setRewriteMethod(new MultiTermQuery.TopTermsScoringBooleanQueryRewrite(maxExpansions));
-
- if (term.text().length() > 1.0f / (1.0f - minimumSimilarity)) {
- this.termLongEnough = true;
- }
-
- this.minimumSimilarity = minimumSimilarity;
- this.prefixLength = prefixLength;
- }
-
- /**
- * Calls {@link #FuzzyQuery(Term, float) FuzzyQuery(term, minimumSimilarity, prefixLength, Integer.MAX_VALUE)}.
- */
- public FuzzyQuery(Term term, float minimumSimilarity, int prefixLength) {
- this(term, minimumSimilarity, prefixLength, defaultMaxExpansions);
- }
-
- /**
- * Calls {@link #FuzzyQuery(Term, float) FuzzyQuery(term, minimumSimilarity, 0, Integer.MAX_VALUE)}.
- */
- public FuzzyQuery(Term term, float minimumSimilarity) {
- this(term, minimumSimilarity, defaultPrefixLength, defaultMaxExpansions);
- }
-
- /**
- * Calls {@link #FuzzyQuery(Term, float) FuzzyQuery(term, 0.5f, 0, Integer.MAX_VALUE)}.
- */
- public FuzzyQuery(Term term) {
- this(term, defaultMinSimilarity, defaultPrefixLength, defaultMaxExpansions);
- }
-
- /**
- * Returns the minimum similarity that is required for this query to match.
- * @return float value between 0.0 and 1.0
- */
- public float getMinSimilarity() {
- return minimumSimilarity;
- }
-
- /**
- * Returns the non-fuzzy prefix length. This is the number of characters at the start
- * of a term that must be identical (not fuzzy) to the query term if the query
- * is to match that term.
- */
- public int getPrefixLength() {
- return prefixLength;
- }
-
- @Override
- protected FilteredTermEnum getEnum(IndexReader reader) throws IOException {
- if (!termLongEnough) { // can only match if it's exact
- return new SingleTermEnum(reader, term);
- }
- return new FuzzyTermEnum(reader, getTerm(), minimumSimilarity, prefixLength);
- }
-
- /**
- * Returns the pattern term.
- */
- public Term getTerm() {
- return term;
- }
-
- @Override
- public String toString(String field) {
- final StringBuilder buffer = new StringBuilder();
- if (!term.field().equals(field)) {
- buffer.append(term.field());
- buffer.append(":");
- }
- buffer.append(term.text());
- buffer.append('~');
- buffer.append(Float.toString(minimumSimilarity));
- buffer.append(ToStringUtils.boost(getBoost()));
- return buffer.toString();
- }
-
- @Override
- public int hashCode() {
- final int prime = 31;
- int result = super.hashCode();
- result = prime * result + Float.floatToIntBits(minimumSimilarity);
- result = prime * result + prefixLength;
- result = prime * result + ((term == null) ? 0 : term.hashCode());
- return result;
- }
-
- @Override
- public boolean equals(Object obj) {
- if (this == obj)
- return true;
- if (!super.equals(obj))
- return false;
- if (getClass() != obj.getClass())
- return false;
- FuzzyQuery other = (FuzzyQuery) obj;
- if (Float.floatToIntBits(minimumSimilarity) != Float
- .floatToIntBits(other.minimumSimilarity))
- return false;
- if (prefixLength != other.prefixLength)
- return false;
- if (term == null) {
- if (other.term != null)
- return false;
- } else if (!term.equals(other.term))
- return false;
- return true;
- }
-
-
-}