pylucene 3.5.0-3

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

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/function/FieldCacheSource.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/function/FieldCacheSource.java
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+package org.apache.lucene.search.function;
+
+/**
+ * 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.
+ */
+
+import java.io.IOException;
+
+import org.apache.lucene.index.IndexReader;
+import org.apache.lucene.search.FieldCache;
+
+/**
+ * Expert: A base class for ValueSource implementations that retrieve values for
+ * a single field from the {@link org.apache.lucene.search.FieldCache FieldCache}.
+ * <p>
+ * Fields used herein must be indexed (doesn't matter if these fields are stored or not).
+ * <p> 
+ * It is assumed that each such indexed field is untokenized, or at least has a single token in a document.
+ * For documents with multiple tokens of the same field, behavior is undefined (It is likely that current 
+ * code would use the value of one of these tokens, but this is not guaranteed).
+ * <p>
+ * Document with no tokens in this field are assigned the <code>Zero</code> value.    
+ * 
+ * @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 abstract class FieldCacheSource extends ValueSource {
+  private String field;
+
+  /**
+   * Create a cached field source for the input field.  
+   */
+  public FieldCacheSource(String field) {
+    this.field=field;
+  }
+
+  /* (non-Javadoc) @see org.apache.lucene.search.function.ValueSource#getValues(org.apache.lucene.index.IndexReader) */
+  @Override
+  public final DocValues getValues(IndexReader reader) throws IOException {
+    return getCachedFieldValues(FieldCache.DEFAULT, field, reader);
+  }
+
+  /* (non-Javadoc) @see org.apache.lucene.search.function.ValueSource#description() */
+  @Override
+  public String description() {
+    return field;
+  }
+
+  /**
+   * Return cached DocValues for input field and reader.
+   * @param cache FieldCache so that values of a field are loaded once per reader (RAM allowing)
+   * @param field Field for which values are required.
+   * @see ValueSource
+   */
+  public abstract DocValues getCachedFieldValues(FieldCache cache, String field, IndexReader reader) throws IOException;
+
+  /*(non-Javadoc) @see java.lang.Object#equals(java.lang.Object) */
+  @Override
+  public final boolean equals(Object o) {
+    if (!(o instanceof FieldCacheSource)) {
+      return false;
+    }
+    FieldCacheSource other = (FieldCacheSource) o;
+    return 
+      this.field.equals(other.field) && 
+      cachedFieldSourceEquals(other);
+  }
+
+  /*(non-Javadoc) @see java.lang.Object#hashCode() */
+  @Override
+  public final int hashCode() {
+    return 
+      field.hashCode() +
+      cachedFieldSourceHashCode();
+  }
+
+  /**
+   * Check if equals to another {@link FieldCacheSource}, already knowing that cache and field are equal.  
+   * @see Object#equals(java.lang.Object)
+   */
+  public abstract boolean cachedFieldSourceEquals(FieldCacheSource other);
+
+  /**
+   * Return a hash code of a {@link FieldCacheSource}, without the hash-codes of the field 
+   * and the cache (those are taken care of elsewhere).  
+   * @see Object#hashCode()
+   */
+  public abstract int cachedFieldSourceHashCode();
+}