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20 using IndexReader = Mono.Lucene.Net.Index.IndexReader;
21 using FieldCache = Mono.Lucene.Net.Search.FieldCache;
23 namespace Mono.Lucene.Net.Search.Function
26 /// <summary> Expert: obtains the ordinal of the field value from the default Lucene
27 /// {@link Mono.Lucene.Net.Search.FieldCache FieldCache} using getStringIndex()
28 /// and reverses the order.
30 /// The native lucene index order is used to assign an ordinal value for each field value.
32 /// Field values (terms) are lexicographically ordered by unicode value, and numbered starting at 1.
34 /// Example of reverse ordinal (rord):
35 /// <br/>If there were only three field values: "apple","banana","pear"
36 /// <br/>then rord("apple")=3, rord("banana")=2, ord("pear")=1
39 /// rord() depends on the position in an index and can thus change
40 /// when other documents are inserted or deleted,
41 /// or if a MultiSearcher is used.
43 /// <p/><font color="#FF0000">
44 /// WARNING: The status of the <b>Search.Function</b> package is experimental.
45 /// The APIs introduced here might change in the future and will not be
46 /// supported anymore in such a case.</font>
48 /// <p/><b>NOTE</b>: with the switch in 2.9 to segment-based
49 /// searching, if {@link #getValues} is invoked with a
50 /// composite (multi-segment) reader, this can easily cause
51 /// double RAM usage for the values in the FieldCache. It's
52 /// best to switch your application to pass only atomic
53 /// (single segment) readers to this API. Alternatively, for
54 /// a short-term fix, you could wrap your ValueSource using
55 /// {@link MultiValueSource}, which costs more CPU per lookup
56 /// but will not consume double the FieldCache RAM.<p/>
60 public class ReverseOrdFieldSource:ValueSource
62 private class AnonymousClassDocValues:DocValues
64 public AnonymousClassDocValues(int end, int[] arr, ReverseOrdFieldSource enclosingInstance)
66 InitBlock(end, arr, enclosingInstance);
68 private void InitBlock(int end, int[] arr, ReverseOrdFieldSource enclosingInstance)
72 this.enclosingInstance = enclosingInstance;
76 private ReverseOrdFieldSource enclosingInstance;
77 public ReverseOrdFieldSource Enclosing_Instance
81 return enclosingInstance;
85 /*(non-Javadoc) @see Mono.Lucene.Net.Search.Function.DocValues#floatVal(int) */
86 public override float FloatVal(int doc)
88 return (float) (end - arr[doc]);
90 /* (non-Javadoc) @see Mono.Lucene.Net.Search.Function.DocValues#intVal(int) */
91 public override int IntVal(int doc)
93 return end - arr[doc];
95 /* (non-Javadoc) @see Mono.Lucene.Net.Search.Function.DocValues#strVal(int) */
96 public override System.String StrVal(int doc)
98 // the string value of the ordinal, not the string itself
99 return System.Convert.ToString(IntVal(doc));
101 /*(non-Javadoc) @see Mono.Lucene.Net.Search.Function.DocValues#toString(int) */
102 public override System.String ToString(int doc)
104 return Enclosing_Instance.Description() + '=' + StrVal(doc);
106 /*(non-Javadoc) @see Mono.Lucene.Net.Search.Function.DocValues#getInnerArray() */
107 public /*internal*/ override System.Object GetInnerArray()
112 public System.String field;
114 /// <summary> Contructor for a certain field.</summary>
115 /// <param name="field">field whose values reverse order is used.
117 public ReverseOrdFieldSource(System.String field)
122 /*(non-Javadoc) @see Mono.Lucene.Net.Search.Function.ValueSource#description() */
123 public override System.String Description()
125 return "rord(" + field + ')';
128 /*(non-Javadoc) @see Mono.Lucene.Net.Search.Function.ValueSource#getValues(Mono.Lucene.Net.Index.IndexReader) */
129 public override DocValues GetValues(IndexReader reader)
131 Mono.Lucene.Net.Search.StringIndex sindex = Mono.Lucene.Net.Search.FieldCache_Fields.DEFAULT.GetStringIndex(reader, field);
133 int[] arr = sindex.order;
134 int end = sindex.lookup.Length;
136 return new AnonymousClassDocValues(end, arr, this);
139 /*(non-Javadoc) @see java.lang.Object#equals(java.lang.Object) */
140 public override bool Equals(System.Object o)
142 if (o.GetType() != typeof(ReverseOrdFieldSource))
144 ReverseOrdFieldSource other = (ReverseOrdFieldSource) o;
145 return this.field.Equals(other.field);
148 private static readonly int hcode;
150 /*(non-Javadoc) @see java.lang.Object#hashCode() */
151 public override int GetHashCode()
153 return hcode + field.GetHashCode();
155 static ReverseOrdFieldSource()
157 hcode = typeof(ReverseOrdFieldSource).GetHashCode();