/*
* Copyright 2004 The Apache Software Foundation
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
using System;
using IndexReader = Lucene.Net.Index.IndexReader;
using Term = Lucene.Net.Index.Term;
namespace Lucene.Net.Search
{
/// Implements the fuzzy search query. The similiarity measurement
/// is based on the Levenshtein (edit distance) algorithm.
///
[Serializable]
public sealed class FuzzyQuery:MultiTermQuery
{
public const float defaultMinSimilarity = 0.5f;
private float minimumSimilarity;
private int prefixLength;
/// 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.
///
///
/// the term to search for
///
/// 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
///
/// length of common (non-fuzzy) prefix
///
/// IllegalArgumentException if minimumSimilarity is > 1 or < 0
/// or if prefixLength < 0 or > term.text().length()
.
///
public FuzzyQuery(Term term, float minimumSimilarity, int prefixLength):base(term)
{
if (minimumSimilarity > 1.0f)
throw new System.ArgumentException("minimumSimilarity > 1");
else if (minimumSimilarity < 0.0f)
throw new System.ArgumentException("minimumSimilarity < 0");
this.minimumSimilarity = minimumSimilarity;
if (prefixLength < 0)
throw new System.ArgumentException("prefixLength < 0");
else if (prefixLength >= term.Text().Length)
throw new System.ArgumentException("prefixLength >= term.text().length()");
this.prefixLength = prefixLength;
}
/// Calls {@link #FuzzyQuery(Term, float) FuzzyQuery(term, minimumSimilarity, 0)}.
public FuzzyQuery(Term term, float minimumSimilarity):this(term, minimumSimilarity, 0)
{
}
/// Calls {@link #FuzzyQuery(Term, float) FuzzyQuery(term, 0.5f, 0)}.
public FuzzyQuery(Term term):this(term, defaultMinSimilarity, 0)
{
}
/// Returns the minimum similarity that is required for this query to match.
/// float value between 0.0 and 1.0
///
public float GetMinSimilarity()
{
return minimumSimilarity;
}
/// Returns the prefix length, i.e. 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;
}
protected internal override FilteredTermEnum GetEnum(IndexReader reader)
{
return new FuzzyTermEnum(reader, GetTerm(), minimumSimilarity, prefixLength);
}
public override System.String ToString(System.String field)
{
return base.ToString(field) + '~' + minimumSimilarity.ToString();
}
}
}