pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / contrib / queryparser / src / java / org / apache / lucene / queryParser / standard / processors / RemoveEmptyNonLeafQueryNodeProcessor.java

diff --git a/lucene-java-3.5.0/lucene/contrib/queryparser/src/java/org/apache/lucene/queryParser/standard/processors/RemoveEmptyNonLeafQueryNodeProcessor.java b/lucene-java-3.5.0/lucene/contrib/queryparser/src/java/org/apache/lucene/queryParser/standard/processors/RemoveEmptyNonLeafQueryNodeProcessor.java
new file mode 100644 (file)
index 0000000..0f182a9
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+++ b/lucene-java-3.5.0/lucene/contrib/queryparser/src/java/org/apache/lucene/queryParser/standard/processors/RemoveEmptyNonLeafQueryNodeProcessor.java
@@ -0,0 +1,116 @@
+package org.apache.lucene.queryParser.standard.processors;
+
+/**
+ * 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.util.LinkedList;
+import java.util.List;
+
+import org.apache.lucene.queryParser.core.QueryNodeException;
+import org.apache.lucene.queryParser.core.nodes.GroupQueryNode;
+import org.apache.lucene.queryParser.core.nodes.MatchNoDocsQueryNode;
+import org.apache.lucene.queryParser.core.nodes.ModifierQueryNode;
+import org.apache.lucene.queryParser.core.nodes.QueryNode;
+import org.apache.lucene.queryParser.core.processors.QueryNodeProcessorImpl;
+
+/**
+ * This processor removes every {@link QueryNode} that is not a leaf and has not
+ * children. If after processing the entire tree the root node is not a leaf and
+ * has no children, a {@link MatchNoDocsQueryNode} object is returned. <br/>
+ * <br/>
+ * This processor is used at the end of a pipeline to avoid invalid query node
+ * tree structures like a {@link GroupQueryNode} or {@link ModifierQueryNode}
+ * with no children. <br/>
+ * 
+ * @see QueryNode
+ * @see MatchNoDocsQueryNode
+ */
+public class RemoveEmptyNonLeafQueryNodeProcessor extends
+    QueryNodeProcessorImpl {
+
+  private LinkedList<QueryNode> childrenBuffer = new LinkedList<QueryNode>();
+
+  public RemoveEmptyNonLeafQueryNodeProcessor() {
+    // empty constructor
+  }
+
+  @Override
+  public QueryNode process(QueryNode queryTree) throws QueryNodeException {
+    queryTree = super.process(queryTree);
+
+    if (!queryTree.isLeaf()) {
+
+      List<QueryNode> children = queryTree.getChildren();
+
+      if (children == null || children.size() == 0) {
+        return new MatchNoDocsQueryNode();
+      }
+
+    }
+
+    return queryTree;
+
+  }
+
+  @Override
+  protected QueryNode postProcessNode(QueryNode node) throws QueryNodeException {
+
+    return node;
+
+  }
+
+  @Override
+  protected QueryNode preProcessNode(QueryNode node) throws QueryNodeException {
+
+    return node;
+
+  }
+
+  @Override
+  protected List<QueryNode> setChildrenOrder(List<QueryNode> children)
+      throws QueryNodeException {
+
+    try {
+
+      for (QueryNode child : children) {
+
+        if (!child.isLeaf()) {
+
+          List<QueryNode> grandChildren = child.getChildren();
+
+          if (grandChildren != null && grandChildren.size() > 0) {
+            this.childrenBuffer.add(child);
+          }
+
+        } else {
+          this.childrenBuffer.add(child);
+        }
+
+      }
+
+      children.clear();
+      children.addAll(this.childrenBuffer);
+
+    } finally {
+      this.childrenBuffer.clear();
+    }
+
+    return children;
+
+  }
+
+}