PrefixQuery.cs

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/* 
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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;
using ToStringUtils = Lucene.Net.Util.ToStringUtils;

namespace Lucene.Net.Search
{
    
    /// <summary>A Query that matches documents containing terms with a specified prefix. A PrefixQuery
    /// is built by QueryParser for input like <c>app*</c>.
    /// 
    /// <p/>This query uses the 
    /// <see cref="MultiTermQuery.CONSTANT_SCORE_AUTO_REWRITE_DEFAULT"/>
    /// rewrite method. 
    /// </summary>
    [Serializable]
    public class PrefixQuery:MultiTermQuery
    {
        private Term prefix;
        
        /// <summary>Constructs a query for terms starting with <c>prefix</c>. </summary>
        public PrefixQuery(Term prefix)
        { //will be removed in 3.0
            this.prefix = prefix;
        }

        /// <summary>Returns the prefix of this query. </summary>
        public virtual Term Prefix
        {
            get { return prefix; }
        }

        protected internal override FilteredTermEnum GetEnum(IndexReader reader)
        {
            return new PrefixTermEnum(reader, prefix);
        }
        
        /// <summary>Prints a user-readable version of this query. </summary>
        public override System.String ToString(System.String field)
        {
            System.Text.StringBuilder buffer = new System.Text.StringBuilder();
            if (!prefix.Field.Equals(field))
            {
                buffer.Append(prefix.Field);
                buffer.Append(":");
            }
            buffer.Append(prefix.Text);
            buffer.Append('*');
            buffer.Append(ToStringUtils.Boost(Boost));
            return buffer.ToString();
        }
        
        //@Override
        public override int GetHashCode()
        {
            int prime = 31;
            int result = base.GetHashCode();
            result = prime * result + ((prefix == null)?0:prefix.GetHashCode());
            return result;
        }
        
        //@Override
        public  override bool Equals(System.Object obj)
        {
            if (this == obj)
                return true;
            if (!base.Equals(obj))
                return false;
            if (GetType() != obj.GetType())
                return false;
            PrefixQuery other = (PrefixQuery) obj;
            if (prefix == null)
            {
                if (other.prefix != null)
                    return false;
            }
            else if (!prefix.Equals(other.prefix))
                return false;
            return true;
        }
    }
}