pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / src / java / org / apache / lucene / search / function / ReverseOrdFieldSource.java

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/function/ReverseOrdFieldSource.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/function/ReverseOrdFieldSource.java
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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.
+ */
+
+package org.apache.lucene.search.function;
+
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.search.FieldCache;
+
+import java.io.IOException;
+
+/**
+ * Expert: obtains the ordinal of the field value from the default Lucene 
+ * {@link org.apache.lucene.search.FieldCache FieldCache} using getStringIndex()
+ * and reverses the order.
+ * <p>
+ * The native lucene index order is used to assign an ordinal value for each field value.
+ * <p>
+ * Field values (terms) are lexicographically ordered by unicode value, and numbered starting at 1.
+ * <br>
+ * Example of reverse ordinal (rord):
+ * <br>If there were only three field values: "apple","banana","pear"
+ * <br>then rord("apple")=3, rord("banana")=2, ord("pear")=1
+ * <p>
+ * WARNING: 
+ * rord() depends on the position in an index and can thus change 
+ * when other documents are inserted or deleted,
+ * or if a MultiSearcher is used. 
+ * 
+ * @lucene.experimental
+ *
+ * <p><b>NOTE</b>: with the switch in 2.9 to segment-based
+ * searching, if {@link #getValues} is invoked with a
+ * composite (multi-segment) reader, this can easily cause
+ * double RAM usage for the values in the FieldCache.  It's
+ * best to switch your application to pass only atomic
+ * (single segment) readers to this API.</p>
+ */
+
+public class ReverseOrdFieldSource extends ValueSource {
+  public String field;
+
+  /** 
+   * Contructor for a certain field.
+   * @param field field whose values reverse order is used.  
+   */
+  public ReverseOrdFieldSource(String field) {
+    this.field = field;
+  }
+
+  /*(non-Javadoc) @see org.apache.lucene.search.function.ValueSource#description() */
+  @Override
+  public String description() {
+    return "rord("+field+')';
+  }
+
+  /*(non-Javadoc) @see org.apache.lucene.search.function.ValueSource#getValues(org.apache.lucene.index.IndexReader) */
+  @Override
+  public DocValues getValues(IndexReader reader) throws IOException {
+    final FieldCache.StringIndex sindex = FieldCache.DEFAULT.getStringIndex(reader, field);
+
+    final int arr[] = sindex.order;
+    final int end = sindex.lookup.length;
+
+    return new DocValues() {
+      /*(non-Javadoc) @see org.apache.lucene.search.function.DocValues#floatVal(int) */
+      @Override
+      public float floatVal(int doc) {
+        return (end - arr[doc]);
+      }
+      /* (non-Javadoc) @see org.apache.lucene.search.function.DocValues#intVal(int) */
+      @Override
+      public int intVal(int doc) {
+        return end - arr[doc];
+      }
+      /* (non-Javadoc) @see org.apache.lucene.search.function.DocValues#strVal(int) */
+      @Override
+      public String strVal(int doc) {
+        // the string value of the ordinal, not the string itself
+        return Integer.toString(intVal(doc));
+      }
+      /*(non-Javadoc) @see org.apache.lucene.search.function.DocValues#toString(int) */
+      @Override
+      public String toString(int doc) {
+        return description() + '=' + strVal(doc);
+      }
+      /*(non-Javadoc) @see org.apache.lucene.search.function.DocValues#getInnerArray() */
+      @Override
+      Object getInnerArray() {
+        return arr;
+      }
+    };
+  }
+
+  /*(non-Javadoc) @see java.lang.Object#equals(java.lang.Object) */
+  @Override
+  public boolean equals(Object o) {
+    if (o == this) return true;
+    if (o == null) return false;
+    if (o.getClass() != ReverseOrdFieldSource.class) return false;
+    ReverseOrdFieldSource other = (ReverseOrdFieldSource)o;
+    return this.field.equals(other.field); 
+  }
+
+  private static final int hcode = ReverseOrdFieldSource.class.hashCode();
+  
+  /*(non-Javadoc) @see java.lang.Object#hashCode() */
+  @Override
+  public int hashCode() {
+    return hcode + field.hashCode();
+  }
+}