pylucene 3.5.0-3

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

diff --git a/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/DocIdSet.java b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/DocIdSet.java
new file mode 100644 (file)
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+++ b/lucene-java-3.5.0/lucene/src/java/org/apache/lucene/search/DocIdSet.java
@@ -0,0 +1,67 @@
+package org.apache.lucene.search;
+
+/**
+ * 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;
+
+/**
+ * A DocIdSet contains a set of doc ids. Implementing classes must
+ * only implement {@link #iterator} to provide access to the set. 
+ */
+public abstract class DocIdSet {
+
+  /** An empty {@code DocIdSet} instance for easy use, e.g. in Filters that hit no documents. */
+  public static final DocIdSet EMPTY_DOCIDSET = new DocIdSet() {
+    
+    private final DocIdSetIterator iterator = new DocIdSetIterator() {
+      @Override
+      public int advance(int target) throws IOException { return NO_MORE_DOCS; }
+      @Override
+      public int docID() { return NO_MORE_DOCS; }
+      @Override
+      public int nextDoc() throws IOException { return NO_MORE_DOCS; }
+    };
+    
+    @Override
+    public DocIdSetIterator iterator() {
+      return iterator;
+    }
+    
+    @Override
+    public boolean isCacheable() {
+      return true;
+    }
+  };
+    
+  /** Provides a {@link DocIdSetIterator} to access the set.
+   * This implementation can return <code>null</code> or
+   * <code>{@linkplain #EMPTY_DOCIDSET}.iterator()</code> if there
+   * are no docs that match. */
+  public abstract DocIdSetIterator iterator() throws IOException;
+
+  /**
+   * This method is a hint for {@link CachingWrapperFilter}, if this <code>DocIdSet</code>
+   * should be cached without copying it into a BitSet. The default is to return
+   * <code>false</code>. If you have an own <code>DocIdSet</code> implementation
+   * that does its iteration very effective and fast without doing disk I/O,
+   * override this method and return <code>true</here>.
+   */
+  public boolean isCacheable() {
+    return false;
+  }
+}