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package org.apache.lucene.queryParser.standard.processors;
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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import java.util.LinkedList;
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import java.util.List;
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import org.apache.lucene.queryParser.core.QueryNodeException;
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import org.apache.lucene.queryParser.core.nodes.GroupQueryNode;
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import org.apache.lucene.queryParser.core.nodes.MatchNoDocsQueryNode;
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import org.apache.lucene.queryParser.core.nodes.ModifierQueryNode;
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import org.apache.lucene.queryParser.core.nodes.QueryNode;
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import org.apache.lucene.queryParser.core.processors.QueryNodeProcessorImpl;
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* This processor removes every {@link QueryNode} that is not a leaf and has not
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* children. If after processing the entire tree the root node is not a leaf and
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* has no children, a {@link MatchNoDocsQueryNode} object is returned. <br/>
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* This processor is used at the end of a pipeline to avoid invalid query node
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* tree structures like a {@link GroupQueryNode} or {@link ModifierQueryNode}
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* with no children. <br/>
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* @see MatchNoDocsQueryNode
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public class RemoveEmptyNonLeafQueryNodeProcessor extends
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QueryNodeProcessorImpl {
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private LinkedList<QueryNode> childrenBuffer = new LinkedList<QueryNode>();
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public RemoveEmptyNonLeafQueryNodeProcessor() {
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public QueryNode process(QueryNode queryTree) throws QueryNodeException {
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queryTree = super.process(queryTree);
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if (!queryTree.isLeaf()) {
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List<QueryNode> children = queryTree.getChildren();
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if (children == null || children.size() == 0) {
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return new MatchNoDocsQueryNode();
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protected QueryNode postProcessNode(QueryNode node) throws QueryNodeException {
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protected QueryNode preProcessNode(QueryNode node) throws QueryNodeException {
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protected List<QueryNode> setChildrenOrder(List<QueryNode> children)
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throws QueryNodeException {
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for (QueryNode child : children) {
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if (!child.isLeaf()) {
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List<QueryNode> grandChildren = child.getChildren();
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if (grandChildren != null && grandChildren.size() > 0) {
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this.childrenBuffer.add(child);
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this.childrenBuffer.add(child);
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children.addAll(this.childrenBuffer);
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this.childrenBuffer.clear();