oak-core/src/test/java/org/apache/jackrabbit/oak/query/UnionQueryTest.java - jackrabbit-oak - Git at Google

 /*
  * 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.jackrabbit.oak.query;

 import static org.apache.jackrabbit.JcrConstants.JCR_PRIMARYTYPE;
 import static org.apache.jackrabbit.oak.api.Type.NAME;
 import static org.apache.jackrabbit.oak.plugins.index.IndexConstants.INDEX_DEFINITIONS_NAME;
 import static org.apache.jackrabbit.oak.plugins.index.IndexConstants.INDEX_DEFINITIONS_NODE_TYPE;
 import static org.apache.jackrabbit.oak.plugins.index.IndexConstants.TYPE_PROPERTY_NAME;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;

 import java.util.Arrays;
 import java.util.List;

 import com.google.common.collect.Lists;
 import org.apache.jackrabbit.oak.InitialContent;
 import org.apache.jackrabbit.oak.Oak;
 import org.apache.jackrabbit.oak.api.ContentRepository;
 import org.apache.jackrabbit.oak.api.QueryEngine;
 import org.apache.jackrabbit.oak.api.Result;
 import org.apache.jackrabbit.oak.api.ResultRow;
 import org.apache.jackrabbit.oak.api.Tree;
 import org.apache.jackrabbit.oak.api.Type;
 import org.apache.jackrabbit.oak.namepath.NamePathMapper;
 import org.apache.jackrabbit.oak.namepath.impl.GlobalNameMapper;
 import org.apache.jackrabbit.oak.namepath.impl.NamePathMapperImpl;
 import org.apache.jackrabbit.oak.plugins.memory.MemoryNodeStore;
 import org.apache.jackrabbit.oak.query.ast.ColumnImpl;
 import org.apache.jackrabbit.oak.query.ast.ConstraintImpl;
 import org.apache.jackrabbit.oak.query.ast.DescendantNodeImpl;
 import org.apache.jackrabbit.oak.query.ast.NodeTypeInfo;
 import org.apache.jackrabbit.oak.query.ast.NodeTypeInfoProvider;
 import org.apache.jackrabbit.oak.query.ast.Order;
 import org.apache.jackrabbit.oak.query.ast.OrderingImpl;
 import org.apache.jackrabbit.oak.query.ast.PropertyValueImpl;
 import org.apache.jackrabbit.oak.query.ast.SelectorImpl;
 import org.apache.jackrabbit.oak.query.ast.SourceImpl;
 import org.apache.jackrabbit.oak.query.stats.QueryStatsData;
 import org.apache.jackrabbit.oak.spi.security.OpenSecurityProvider;
 import org.junit.After;
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.Mockito;

 public class UnionQueryTest extends AbstractQueryTest {

     MemoryNodeStore store;
     QueryEngineSettings qeSettings;

     @Override
     protected ContentRepository createRepository() {
         store = new MemoryNodeStore();
         qeSettings = new QueryEngineSettings();

         return new Oak(store)
                 .with(new OpenSecurityProvider())
                 .with(new InitialContent())
                 .with(qeSettings)
                 .createContentRepository();
     }

     @Before
     @Override
     public void before() throws Exception {
         super.before();

         // Create tree for this test
         Tree t = root.getTree("/").addChild("UnionQueryTest");

         // Create tree /a/b/c/d/e
         t = t.addChild("a");
         t = t.addChild("b");
         t = t.addChild("c");
         t = t.addChild("d");
         t = t.addChild("e");

         Tree t2 = root.getTree("/").addChild("UnionQueryTest2");
         Tree t3 = t2.addChild("a");

         root.commit();
     }

     @After
     public void after() throws Exception {
         // Remove test tree
         root.getTree("/UnionQueryTest").remove();
         root.commit();
     }

     @Test
     public void testMergeSortedVsConcat() throws  Exception {
         String left = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest2')";
         String right = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest/a')";
         String order = "ORDER BY [jcr:path]";
         String union = String.format("%s UNION %s %s", left, right, order);
         final int limit = 10;
         final int offset = 0;
         // Execute query with ORDER BY clause - This should use mergeSorted and the final result should be sorted across both the subqueries.
         String[] expected = {
                 "/UnionQueryTest/a/b",
                 "/UnionQueryTest/a/b/c",
                 "/UnionQueryTest/a/b/c/d",
                 "/UnionQueryTest/a/b/c/d/e",
                 "/UnionQueryTest2/a"
         };

         Result result = qe.executeQuery(union, QueryEngineImpl.SQL2, limit, offset,
                 QueryEngine.NO_BINDINGS, QueryEngine.NO_MAPPINGS);
         int i = 0;
         for (ResultRow rr: result.getRows()) {
             assertEquals(rr.getPath(), expected[i++]);

         }

         // Now we execute the same union query without the order by clause. Expectation is the subqueries results should simply be concatenated without
         // sorting of the overall result
         String[] expected2 = {
                 "/UnionQueryTest2/a",
                 "/UnionQueryTest/a/b",
                 "/UnionQueryTest/a/b/c",
                 "/UnionQueryTest/a/b/c/d",
                 "/UnionQueryTest/a/b/c/d/e"
         };

         union = String.format("%s UNION %s", left, right);

         result = qe.executeQuery(union, QueryEngineImpl.SQL2, limit, offset,
                 QueryEngine.NO_BINDINGS, QueryEngine.NO_MAPPINGS);
          i = 0;
         for (ResultRow rr: result.getRows()) {
             assertEquals(rr.getPath(), expected2[i++]);
         }

     }
     // TODO - Write a similar test that might fail with guava's merge sort on some conditions
     @Test
     public void testSortWithOneSubquerySortedByIndexAndOtherNot() throws Exception {

         String left  = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest2')";
         String right  = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest/a')";

         NodeTypeInfoProvider nodeTypes = new NodeStateNodeTypeInfoProvider(store.getRoot());
         NodeTypeInfo type = nodeTypes.getNodeTypeInfo("nt:base");
         SourceImpl sImpl = new SelectorImpl(type, "a");
         SourceImpl sImpl2 = new SelectorImpl(type, "a");
         SourceImpl sImpl3 = new SelectorImpl(type, "a");

         QueryImpl qImplLeft = createQuery(left, new DescendantNodeImpl("a","/UnionQueryTest2"), sImpl);
         qImplLeft.setExecutionContext(((QueryEngineImpl)root.getQueryEngine()).getExecutionContext());
         QueryImpl qImplRight = createQuery(right, new DescendantNodeImpl("a","/UnionQueryTest/a"), sImpl2);
         qImplRight.setExecutionContext(((QueryEngineImpl)root.getQueryEngine()).getExecutionContext());

         PropertyValueImpl propValImpl = new PropertyValueImpl("a", "jcr:path");
         propValImpl.bindSelector(sImpl);

         PropertyValueImpl propValImpl2 = new PropertyValueImpl("a", "jcr:path");
         propValImpl2.bindSelector(sImpl2);

         PropertyValueImpl propValImpl3 = new PropertyValueImpl("a", "jcr:path");
         propValImpl2.bindSelector(sImpl3);

         /// One subquery sorted by index and the other not and orderBY != null in UnionQueryImpl
         QueryImpl spyLeft = Mockito.spy(qImplLeft);
         QueryImpl spyRight = Mockito.spy(qImplRight);
         Mockito.doReturn(true).when(spyLeft).isSortedByIndex();
         Mockito.doReturn(false).when(spyRight).isSortedByIndex();

         spyLeft.setOrderings(new OrderingImpl[] {new OrderingImpl(propValImpl, Order.DESCENDING)});
         spyRight.setOrderings(new OrderingImpl[] {new OrderingImpl(propValImpl2, Order.DESCENDING)});
         UnionQueryImpl unionImpl = new UnionQueryImpl(true, spyLeft, spyRight, new QueryEngineSettings());
         unionImpl.setOrderings(new OrderingImpl[] {new OrderingImpl(propValImpl3, Order.ASCENDING)});

         unionImpl.init();

         // Execute query with ORDER BY clause - This should use mergeSorted and the final result should be sorted across both the subqueries.
         String[] expected = {
                 "/UnionQueryTest/a/b",
                 "/UnionQueryTest/a/b/c",
                 "/UnionQueryTest/a/b/c/d",
                 "/UnionQueryTest/a/b/c/d/e",
                 "/UnionQueryTest2/a"
         };

         Result result = unionImpl.executeQuery();

         int i = 0;
         for (ResultRow rr: result.getRows()) {
             assertEquals(expected[i++], rr.getPath());
         }

     }

     @Test
     public void testOrderLimitOffset() throws Exception {
         String left = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest')";
         String right = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest')";
         String order = "ORDER BY [jcr:path]";
         String union = String.format("%s UNION %s %s", left, right, order);

         final int limit = 3;
         final int offset = 2;

         String[] expected = {
                 "/UnionQueryTest/a/b/c",
                 "/UnionQueryTest/a/b/c/d",
                 "/UnionQueryTest/a/b/c/d/e"
         };

         Result result = qe.executeQuery(union, QueryEngineImpl.SQL2, limit, offset,
                 QueryEngine.NO_BINDINGS, QueryEngine.NO_MAPPINGS);

         List<ResultRow> rows = Lists.newArrayList(result.getRows());
         assertEquals(expected.length, rows.size());

         int i = 0;
         for (ResultRow rr: result.getRows()) {
             assertEquals(rr.getPath(), expected[i++]);
         }
     }

     @Test
     public void testExplainStatement() throws Exception {
         final String left = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest')";
         final String right = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest')";
         final String order = "ORDER BY [jcr:path]";
         final String union = String.format("%s UNION %s %s", left, right, order);
         final String explainUnion = "explain " + union;

         Result explainResult = executeQuery(explainUnion, QueryEngineImpl.SQL2, QueryEngine.NO_BINDINGS);

         int explainCount = 0;
         ResultRow explainRow = null;
         for (ResultRow row : explainResult.getRows()) {
             if (explainCount == 0) {
                 explainRow = row;
             }
             explainCount = explainCount + 1;
         }

         assertEquals("should exist 1 result", 1, explainCount);
         assertNotNull("explain row should not be null", explainRow);

         assertTrue("result should have 'plan' column",
                 Arrays.asList(explainResult.getColumnNames()).contains("plan"));
         assertTrue("result should have 'statement' column",
                 Arrays.asList(explainResult.getColumnNames()).contains("statement"));

         final String explainedStatement = explainRow.getValue("statement").getValue(Type.STRING);

         assertTrue("'statement' should begin with 'select': " + explainedStatement,
                 explainedStatement.startsWith("SELECT"));
         assertTrue("'statement' should contain ' UNION ': " + explainedStatement,
                 explainedStatement.contains(" UNION "));

         final int limit = 3;
         final int offset = 2;

         String[] expected = {
                 "/UnionQueryTest/a/b/c",
                 "/UnionQueryTest/a/b/c/d",
                 "/UnionQueryTest/a/b/c/d/e"
         };

         Result result = qe.executeQuery(explainedStatement, QueryEngineImpl.SQL2, limit, offset,
                 QueryEngine.NO_BINDINGS, QueryEngine.NO_MAPPINGS);

         List<ResultRow> rows = Lists.newArrayList(result.getRows());
         assertEquals(expected.length, rows.size());

         int i = 0;
         for (ResultRow rr: result.getRows()) {
             assertEquals(rr.getPath(), expected[i++]);
         }
     }

     @Test
     public void testExplainStatementXPath() throws Exception {
         final String xpath = "/jcr:root/UnionQueryTest//(element(*, nt:base) | element(*, nt:folder)) order by jcr:path";
         final String explainUnion = "explain " + xpath;

         Result explainResult = executeQuery(explainUnion, QueryEngineImpl.XPATH, QueryEngine.NO_BINDINGS);

         int explainCount = 0;
         ResultRow explainRow = null;
         for (ResultRow row : explainResult.getRows()) {
             if (explainCount == 0) {
                 explainRow = row;
             }
             explainCount = explainCount + 1;
         }

         assertEquals("should exist 1 result", 1, explainCount);
         assertNotNull("explain row should not be null", explainRow);

         assertTrue("result should have 'plan' column",
                 Arrays.asList(explainResult.getColumnNames()).contains("plan"));
         assertTrue("result should have 'statement' column",
                 Arrays.asList(explainResult.getColumnNames()).contains("statement"));

         final String explainedStatement = explainRow.getValue("statement").getValue(Type.STRING);
         assertTrue("'statement' should begin with 'select': " + explainedStatement,
                 explainedStatement.startsWith("select"));
         assertTrue("'statement' should contain ' union ': " + explainedStatement,
                 explainedStatement.contains(" union "));

         final int limit = 3;
         final int offset = 2;

         String[] expected = {
                 "/UnionQueryTest/a/b/c",
                 "/UnionQueryTest/a/b/c/d",
                 "/UnionQueryTest/a/b/c/d/e"
         };

         Result result = qe.executeQuery(explainedStatement, QueryEngineImpl.SQL2, limit, offset,
                 QueryEngine.NO_BINDINGS, QueryEngine.NO_MAPPINGS);

         List<ResultRow> rows = Lists.newArrayList(result.getRows());
         assertEquals(expected.length, rows.size());

         int i = 0;
         for (ResultRow rr: result.getRows()) {
             assertEquals(rr.getPath(), expected[i++]);
         }
     }

     private QueryImpl createQuery (String statement, ConstraintImpl c, SourceImpl sImpl) throws Exception {

         NamePathMapper namePathMapper = new NamePathMapperImpl(new GlobalNameMapper(root));
         return new QueryImpl(statement, sImpl, c,
                 new ColumnImpl[]{new ColumnImpl("a", "jcr:path", "jcr:path")}, namePathMapper, qeSettings, new QueryStatsData("", "").new QueryExecutionStats());

     }
 }
	/*
	* 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.jackrabbit.oak.query;

	import static org.apache.jackrabbit.JcrConstants.JCR_PRIMARYTYPE;
	import static org.apache.jackrabbit.oak.api.Type.NAME;
	import static org.apache.jackrabbit.oak.plugins.index.IndexConstants.INDEX_DEFINITIONS_NAME;
	import static org.apache.jackrabbit.oak.plugins.index.IndexConstants.INDEX_DEFINITIONS_NODE_TYPE;
	import static org.apache.jackrabbit.oak.plugins.index.IndexConstants.TYPE_PROPERTY_NAME;
	import static org.junit.Assert.assertEquals;
	import static org.junit.Assert.assertNotNull;
	import static org.junit.Assert.assertTrue;

	import java.util.Arrays;
	import java.util.List;

	import com.google.common.collect.Lists;
	import org.apache.jackrabbit.oak.InitialContent;
	import org.apache.jackrabbit.oak.Oak;
	import org.apache.jackrabbit.oak.api.ContentRepository;
	import org.apache.jackrabbit.oak.api.QueryEngine;
	import org.apache.jackrabbit.oak.api.Result;
	import org.apache.jackrabbit.oak.api.ResultRow;
	import org.apache.jackrabbit.oak.api.Tree;
	import org.apache.jackrabbit.oak.api.Type;
	import org.apache.jackrabbit.oak.namepath.NamePathMapper;
	import org.apache.jackrabbit.oak.namepath.impl.GlobalNameMapper;
	import org.apache.jackrabbit.oak.namepath.impl.NamePathMapperImpl;
	import org.apache.jackrabbit.oak.plugins.memory.MemoryNodeStore;
	import org.apache.jackrabbit.oak.query.ast.ColumnImpl;
	import org.apache.jackrabbit.oak.query.ast.ConstraintImpl;
	import org.apache.jackrabbit.oak.query.ast.DescendantNodeImpl;
	import org.apache.jackrabbit.oak.query.ast.NodeTypeInfo;
	import org.apache.jackrabbit.oak.query.ast.NodeTypeInfoProvider;
	import org.apache.jackrabbit.oak.query.ast.Order;
	import org.apache.jackrabbit.oak.query.ast.OrderingImpl;
	import org.apache.jackrabbit.oak.query.ast.PropertyValueImpl;
	import org.apache.jackrabbit.oak.query.ast.SelectorImpl;
	import org.apache.jackrabbit.oak.query.ast.SourceImpl;
	import org.apache.jackrabbit.oak.query.stats.QueryStatsData;
	import org.apache.jackrabbit.oak.spi.security.OpenSecurityProvider;
	import org.junit.After;
	import org.junit.Before;
	import org.junit.Test;
	import org.mockito.Mockito;

	public class UnionQueryTest extends AbstractQueryTest {

	MemoryNodeStore store;
	QueryEngineSettings qeSettings;

	@Override
	protected ContentRepository createRepository() {
	store = new MemoryNodeStore();
	qeSettings = new QueryEngineSettings();

	return new Oak(store)
	.with(new OpenSecurityProvider())
	.with(new InitialContent())
	.with(qeSettings)
	.createContentRepository();
	}

	@Before
	@Override
	public void before() throws Exception {
	super.before();

	// Create tree for this test
	Tree t = root.getTree("/").addChild("UnionQueryTest");

	// Create tree /a/b/c/d/e
	t = t.addChild("a");
	t = t.addChild("b");
	t = t.addChild("c");
	t = t.addChild("d");
	t = t.addChild("e");

	Tree t2 = root.getTree("/").addChild("UnionQueryTest2");
	Tree t3 = t2.addChild("a");

	root.commit();
	}

	@After
	public void after() throws Exception {
	// Remove test tree
	root.getTree("/UnionQueryTest").remove();
	root.commit();
	}

	@Test
	public void testMergeSortedVsConcat() throws Exception {
	String left = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest2')";
	String right = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest/a')";
	String order = "ORDER BY [jcr:path]";
	String union = String.format("%s UNION %s %s", left, right, order);
	final int limit = 10;
	final int offset = 0;
	// Execute query with ORDER BY clause - This should use mergeSorted and the final result should be sorted across both the subqueries.
	String[] expected = {
	"/UnionQueryTest/a/b",
	"/UnionQueryTest/a/b/c",
	"/UnionQueryTest/a/b/c/d",
	"/UnionQueryTest/a/b/c/d/e",
	"/UnionQueryTest2/a"
	};

	Result result = qe.executeQuery(union, QueryEngineImpl.SQL2, limit, offset,
	QueryEngine.NO_BINDINGS, QueryEngine.NO_MAPPINGS);
	int i = 0;
	for (ResultRow rr: result.getRows()) {
	assertEquals(rr.getPath(), expected[i++]);

	}

	// Now we execute the same union query without the order by clause. Expectation is the subqueries results should simply be concatenated without
	// sorting of the overall result
	String[] expected2 = {
	"/UnionQueryTest2/a",
	"/UnionQueryTest/a/b",
	"/UnionQueryTest/a/b/c",
	"/UnionQueryTest/a/b/c/d",
	"/UnionQueryTest/a/b/c/d/e"
	};

	union = String.format("%s UNION %s", left, right);

	result = qe.executeQuery(union, QueryEngineImpl.SQL2, limit, offset,
	QueryEngine.NO_BINDINGS, QueryEngine.NO_MAPPINGS);
	i = 0;
	for (ResultRow rr: result.getRows()) {
	assertEquals(rr.getPath(), expected2[i++]);
	}

	}
	// TODO - Write a similar test that might fail with guava's merge sort on some conditions
	@Test
	public void testSortWithOneSubquerySortedByIndexAndOtherNot() throws Exception {

	String left = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest2')";
	String right = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest/a')";

	NodeTypeInfoProvider nodeTypes = new NodeStateNodeTypeInfoProvider(store.getRoot());
	NodeTypeInfo type = nodeTypes.getNodeTypeInfo("nt:base");
	SourceImpl sImpl = new SelectorImpl(type, "a");
	SourceImpl sImpl2 = new SelectorImpl(type, "a");
	SourceImpl sImpl3 = new SelectorImpl(type, "a");

	QueryImpl qImplLeft = createQuery(left, new DescendantNodeImpl("a","/UnionQueryTest2"), sImpl);
	qImplLeft.setExecutionContext(((QueryEngineImpl)root.getQueryEngine()).getExecutionContext());
	QueryImpl qImplRight = createQuery(right, new DescendantNodeImpl("a","/UnionQueryTest/a"), sImpl2);
	qImplRight.setExecutionContext(((QueryEngineImpl)root.getQueryEngine()).getExecutionContext());

	PropertyValueImpl propValImpl = new PropertyValueImpl("a", "jcr:path");
	propValImpl.bindSelector(sImpl);

	PropertyValueImpl propValImpl2 = new PropertyValueImpl("a", "jcr:path");
	propValImpl2.bindSelector(sImpl2);

	PropertyValueImpl propValImpl3 = new PropertyValueImpl("a", "jcr:path");
	propValImpl2.bindSelector(sImpl3);

	/// One subquery sorted by index and the other not and orderBY != null in UnionQueryImpl
	QueryImpl spyLeft = Mockito.spy(qImplLeft);
	QueryImpl spyRight = Mockito.spy(qImplRight);
	Mockito.doReturn(true).when(spyLeft).isSortedByIndex();
	Mockito.doReturn(false).when(spyRight).isSortedByIndex();

	spyLeft.setOrderings(new OrderingImpl[] {new OrderingImpl(propValImpl, Order.DESCENDING)});
	spyRight.setOrderings(new OrderingImpl[] {new OrderingImpl(propValImpl2, Order.DESCENDING)});
	UnionQueryImpl unionImpl = new UnionQueryImpl(true, spyLeft, spyRight, new QueryEngineSettings());
	unionImpl.setOrderings(new OrderingImpl[] {new OrderingImpl(propValImpl3, Order.ASCENDING)});

	unionImpl.init();

	// Execute query with ORDER BY clause - This should use mergeSorted and the final result should be sorted across both the subqueries.
	String[] expected = {
	"/UnionQueryTest/a/b",
	"/UnionQueryTest/a/b/c",
	"/UnionQueryTest/a/b/c/d",
	"/UnionQueryTest/a/b/c/d/e",
	"/UnionQueryTest2/a"
	};

	Result result = unionImpl.executeQuery();

	int i = 0;
	for (ResultRow rr: result.getRows()) {
	assertEquals(expected[i++], rr.getPath());
	}

	}

	@Test
	public void testOrderLimitOffset() throws Exception {
	String left = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest')";
	String right = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest')";
	String order = "ORDER BY [jcr:path]";
	String union = String.format("%s UNION %s %s", left, right, order);

	final int limit = 3;
	final int offset = 2;

	String[] expected = {
	"/UnionQueryTest/a/b/c",
	"/UnionQueryTest/a/b/c/d",
	"/UnionQueryTest/a/b/c/d/e"
	};

	Result result = qe.executeQuery(union, QueryEngineImpl.SQL2, limit, offset,
	QueryEngine.NO_BINDINGS, QueryEngine.NO_MAPPINGS);

	List<ResultRow> rows = Lists.newArrayList(result.getRows());
	assertEquals(expected.length, rows.size());

	int i = 0;
	for (ResultRow rr: result.getRows()) {
	assertEquals(rr.getPath(), expected[i++]);
	}
	}

	@Test
	public void testExplainStatement() throws Exception {
	final String left = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest')";
	final String right = "SELECT [jcr:path] FROM [nt:base] AS a WHERE ISDESCENDANTNODE(a, '/UnionQueryTest')";
	final String order = "ORDER BY [jcr:path]";
	final String union = String.format("%s UNION %s %s", left, right, order);
	final String explainUnion = "explain " + union;

	Result explainResult = executeQuery(explainUnion, QueryEngineImpl.SQL2, QueryEngine.NO_BINDINGS);

	int explainCount = 0;
	ResultRow explainRow = null;
	for (ResultRow row : explainResult.getRows()) {
	if (explainCount == 0) {
	explainRow = row;
	}
	explainCount = explainCount + 1;
	}

	assertEquals("should exist 1 result", 1, explainCount);
	assertNotNull("explain row should not be null", explainRow);

	assertTrue("result should have 'plan' column",
	Arrays.asList(explainResult.getColumnNames()).contains("plan"));
	assertTrue("result should have 'statement' column",
	Arrays.asList(explainResult.getColumnNames()).contains("statement"));

	final String explainedStatement = explainRow.getValue("statement").getValue(Type.STRING);

	assertTrue("'statement' should begin with 'select': " + explainedStatement,
	explainedStatement.startsWith("SELECT"));
	assertTrue("'statement' should contain ' UNION ': " + explainedStatement,
	explainedStatement.contains(" UNION "));

	final int limit = 3;
	final int offset = 2;

	String[] expected = {
	"/UnionQueryTest/a/b/c",
	"/UnionQueryTest/a/b/c/d",
	"/UnionQueryTest/a/b/c/d/e"
	};

	Result result = qe.executeQuery(explainedStatement, QueryEngineImpl.SQL2, limit, offset,
	QueryEngine.NO_BINDINGS, QueryEngine.NO_MAPPINGS);

	List<ResultRow> rows = Lists.newArrayList(result.getRows());
	assertEquals(expected.length, rows.size());

	int i = 0;
	for (ResultRow rr: result.getRows()) {
	assertEquals(rr.getPath(), expected[i++]);
	}
	}

	@Test
	public void testExplainStatementXPath() throws Exception {
	final String xpath = "/jcr:root/UnionQueryTest//(element(, nt:base) \| element(, nt:folder)) order by jcr:path";
	final String explainUnion = "explain " + xpath;

	Result explainResult = executeQuery(explainUnion, QueryEngineImpl.XPATH, QueryEngine.NO_BINDINGS);

	int explainCount = 0;
	ResultRow explainRow = null;
	for (ResultRow row : explainResult.getRows()) {
	if (explainCount == 0) {
	explainRow = row;
	}
	explainCount = explainCount + 1;
	}

	assertEquals("should exist 1 result", 1, explainCount);
	assertNotNull("explain row should not be null", explainRow);

	assertTrue("result should have 'plan' column",
	Arrays.asList(explainResult.getColumnNames()).contains("plan"));
	assertTrue("result should have 'statement' column",
	Arrays.asList(explainResult.getColumnNames()).contains("statement"));

	final String explainedStatement = explainRow.getValue("statement").getValue(Type.STRING);
	assertTrue("'statement' should begin with 'select': " + explainedStatement,
	explainedStatement.startsWith("select"));
	assertTrue("'statement' should contain ' union ': " + explainedStatement,
	explainedStatement.contains(" union "));

	final int limit = 3;
	final int offset = 2;

	String[] expected = {
	"/UnionQueryTest/a/b/c",
	"/UnionQueryTest/a/b/c/d",
	"/UnionQueryTest/a/b/c/d/e"
	};

	Result result = qe.executeQuery(explainedStatement, QueryEngineImpl.SQL2, limit, offset,
	QueryEngine.NO_BINDINGS, QueryEngine.NO_MAPPINGS);

	List<ResultRow> rows = Lists.newArrayList(result.getRows());
	assertEquals(expected.length, rows.size());

	int i = 0;
	for (ResultRow rr: result.getRows()) {
	assertEquals(rr.getPath(), expected[i++]);
	}
	}

	private QueryImpl createQuery (String statement, ConstraintImpl c, SourceImpl sImpl) throws Exception {

	NamePathMapper namePathMapper = new NamePathMapperImpl(new GlobalNameMapper(root));
	return new QueryImpl(statement, sImpl, c,
	new ColumnImpl[]{new ColumnImpl("a", "jcr:path", "jcr:path")}, namePathMapper, qeSettings, new QueryStatsData("", "").new QueryExecutionStats());

	}
	}