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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 Lucene.Net.Support;
namespace Lucene.Net.Search
{
/// <summary> Encapsulates sort criteria for returned hits.
///
/// <p/>The fields used to determine sort order must be carefully chosen.
/// Documents must contain a single term in such a field,
/// and the value of the term should indicate the document's relative position in
/// a given sort order. The field must be indexed, but should not be tokenized,
/// and does not need to be stored (unless you happen to want it back with the
/// rest of your document data). In other words:
///
/// <p/><c>document.add (new Field ("byNumber", Integer.toString(x), Field.Store.NO, Field.Index.NOT_ANALYZED));</c><p/>
///
///
/// <p/><h3>Valid Types of Values</h3>
///
/// <p/>There are four possible kinds of term values which may be put into
/// sorting fields: Integers, Longs, Floats, or Strings. Unless
/// <see cref="SortField">SortField</see> objects are specified, the type of value
/// in the field is determined by parsing the first term in the field.
///
/// <p/>Integer term values should contain only digits and an optional
/// preceding negative sign. Values must be base 10 and in the range
/// <c>Integer.MIN_VALUE</c> and <c>Integer.MAX_VALUE</c> inclusive.
/// Documents which should appear first in the sort
/// should have low value integers, later documents high values
/// (i.e. the documents should be numbered <c>1..n</c> where
/// <c>1</c> is the first and <c>n</c> the last).
///
/// <p/>Long term values should contain only digits and an optional
/// preceding negative sign. Values must be base 10 and in the range
/// <c>Long.MIN_VALUE</c> and <c>Long.MAX_VALUE</c> inclusive.
/// Documents which should appear first in the sort
/// should have low value integers, later documents high values.
///
/// <p/>Float term values should conform to values accepted by
/// <see cref="float.Parse(string)" /> (except that <c>NaN</c>
/// and <c>Infinity</c> are not supported).
/// Documents which should appear first in the sort
/// should have low values, later documents high values.
///
/// <p/>String term values can contain any valid String, but should
/// not be tokenized. The values are sorted according to their
/// <see cref="IComparable">natural order</see>. Note that using this type
/// of term value has higher memory requirements than the other
/// two types.
///
/// <p/><h3>Object Reuse</h3>
///
/// <p/>One of these objects can be
/// used multiple times and the sort order changed between usages.
///
/// <p/>This class is thread safe.
///
/// <p/><h3>Memory Usage</h3>
///
/// <p/>Sorting uses of caches of term values maintained by the
/// internal HitQueue(s). The cache is static and contains an integer
/// or float array of length <c>IndexReader.MaxDoc</c> for each field
/// name for which a sort is performed. In other words, the size of the
/// cache in bytes is:
///
/// <p/><c>4 * IndexReader.MaxDoc * (# of different fields actually used to sort)</c>
///
/// <p/>For String fields, the cache is larger: in addition to the
/// above array, the value of every term in the field is kept in memory.
/// If there are many unique terms in the field, this could
/// be quite large.
///
/// <p/>Note that the size of the cache is not affected by how many
/// fields are in the index and <i>might</i> be used to sort - only by
/// the ones actually used to sort a result set.
///
/// <p/>Created: Feb 12, 2004 10:53:57 AM
///
/// </summary>
[Serializable]
public class Sort
{
/// <summary> Represents sorting by computed relevance. Using this sort criteria returns
/// the same results as calling
/// <see cref="Searcher.Search(Query,int)" />Searcher#search()without a sort criteria,
/// only with slightly more overhead.
/// </summary>
public static readonly Sort RELEVANCE = new Sort();
/// <summary>Represents sorting by index order. </summary>
public static readonly Sort INDEXORDER;
// internal representation of the sort criteria
internal SortField[] fields;
/// <summary> Sorts by computed relevance. This is the same sort criteria as calling
/// <see cref="Searcher.Search(Query,int)" />without a sort criteria,
/// only with slightly more overhead.
/// </summary>
public Sort():this(SortField.FIELD_SCORE)
{
}
/// <summary>Sorts by the criteria in the given SortField. </summary>
public Sort(SortField field)
{
SetSort(field);
}
/// <summary>Sorts in succession by the criteria in each SortField. </summary>
public Sort(params SortField[] fields)
{
SetSort(fields);
}
/// <summary>Sets the sort to the given criteria. </summary>
public virtual void SetSort(SortField field)
{
this.fields = new SortField[]{field};
}
/// <summary>Sets the sort to the given criteria in succession. </summary>
public virtual void SetSort(params SortField[] fields)
{
this.fields = fields;
}
/// <summary> Representation of the sort criteria.</summary>
/// <returns> Array of SortField objects used in this sort criteria
/// </returns>
public virtual SortField[] GetSort()
{
return fields;
}
public override System.String ToString()
{
System.Text.StringBuilder buffer = new System.Text.StringBuilder();
for (int i = 0; i < fields.Length; i++)
{
buffer.Append(fields[i].ToString());
if ((i + 1) < fields.Length)
buffer.Append(',');
}
return buffer.ToString();
}
/// <summary>Returns true if <c>o</c> is equal to this. </summary>
public override bool Equals(System.Object o)
{
if (this == o)
return true;
if (!(o is Sort))
return false;
Sort other = (Sort) o;
bool result = false;
if ((this.fields == null) && (other.fields == null))
result = true;
else if ((this.fields != null) && (other.fields != null))
{
if (this.fields.Length == other.fields.Length)
{
int length = this.fields.Length;
result = true;
for (int i = 0; i < length; i++)
{
if (!(this.fields[i].Equals(other.fields[i])))
{
result = false;
break;
}
}
}
}
return result;
}
/// <summary>Returns a hash code value for this object. </summary>
public override int GetHashCode()
{
// TODO in Java 1.5: switch to Arrays.hashCode(). The
// Java 1.4 workaround below calculates the same hashCode
// as Java 1.5's new Arrays.hashCode()
return 0x45aaf665 + EquatableList<SortField>.GetHashCode(fields);
}
static Sort()
{
INDEXORDER = new Sort(SortField.FIELD_DOC);
}
}
}
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