/*
* 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;
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><code>document.add (new Field ("byNumber", Integer.toString(x), Field.Store.NO, Field.Index.UN_TOKENIZED));</code></p>
///
///
/// <p><h3>Valid Types of Values</h3>
///
/// <p>There are three possible kinds of term values which may be put into
/// sorting fields: Integers, Floats, or Strings. Unless
/// {@link SortField SortField} 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
/// preceeding negative sign. Values must be base 10 and in the range
/// <code>Integer.MIN_VALUE</code> and <code>Integer.MAX_VALUE</code> 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 <code>1..n</code> where
/// <code>1</code> is the first and <code>n</code> the last).
///
/// <p>Float term values should conform to values accepted by
/// {@link Float Float.valueOf(String)} (except that <code>NaN</code>
/// and <code>Infinity</code> 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
/// {@link Comparable natural order}. 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 <code>IndexReader.maxDoc()</code> for each field
/// name for which a sort is performed. In other words, the size of the
/// cache in bytes is:
///
/// <p><code>4 * IndexReader.maxDoc() * (# of different fields actually used to sort)</code>
///
/// <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>The cache is cleared each time a new <code>IndexReader</code> is
/// passed in, or if the value returned by <code>maxDoc()</code>
/// changes for the current IndexReader. This class is not set up to
/// be able to efficiently sort hits from more than one index
/// simultaneously.
///
/// <p>Created: Feb 12, 2004 10:53:57 AM
///
/// </summary>
/// <author> Tim Jones (Nacimiento Software)
/// </author>
/// <since> lucene 1.4
/// </since>
/// <version> $Id: Sort.java 150618 2004-10-18 22:36:54Z dnaber $
/// </version>
[Serializable]
public class Sort
{
/// <summary> Represents sorting by computed relevance. Using this sort criteria returns
/// the same results as calling
/// {@link Searcher#Search(Query) 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
/// {@link Searcher#Search(Query) Searcher#search()}without a sort criteria,
/// only with slightly more overhead.
/// </summary>
public Sort():this(new SortField[]{SortField.FIELD_SCORE, SortField.FIELD_DOC})
{
}
/// <summary> Sorts by the terms in <code>field</code> then by index order (document
/// number). The type of value in <code>field</code> is determined
/// automatically.
///
/// </summary>
/// <seealso cref="SortField.AUTO">
/// </seealso>
public Sort(System.String field)
{
SetSort(field, false);
}
/// <summary> Sorts possibly in reverse by the terms in <code>field</code> then by
/// index order (document number). The type of value in <code>field</code> is
/// determined automatically.
///
/// </summary>
/// <seealso cref="SortField.AUTO">
/// </seealso>
public Sort(System.String field, bool reverse)
{
SetSort(field, reverse);
}
/// <summary> Sorts in succession by the terms in each field. The type of value in
/// <code>field</code> is determined automatically.
///
/// </summary>
/// <seealso cref="SortField.AUTO">
/// </seealso>
public Sort(System.String[] fields)
{
SetSort(fields);
}
/// <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(SortField[] fields)
{
SetSort(fields);
}
/// <summary> Sets the sort to the terms in <code>field</code> then by index order
/// (document number).
/// </summary>
public void SetSort(System.String field)
{
SetSort(field, false);
}
/// <summary> Sets the sort to the terms in <code>field</code> possibly in reverse,
/// then by index order (document number).
/// </summary>
public virtual void SetSort(System.String field, bool reverse)
{
SortField[] nfields = new SortField[]{new SortField(field, SortField.AUTO, reverse), SortField.FIELD_DOC};
fields = nfields;
}
/// <summary>Sets the sort to the terms in each field in succession. </summary>
public virtual void SetSort(System.String[] fieldnames)
{
int n = fieldnames.Length;
SortField[] nfields = new SortField[n];
for (int i = 0; i < n; ++i)
{
nfields[i] = new SortField(fieldnames[i], SortField.AUTO);
}
fields = nfields;
}
/// <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(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();
}
static Sort()
{
INDEXORDER = new Sort(SortField.FIELD_DOC);
}
}
}
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