1 /*
2 * ModeShape (http://www.modeshape.org)
3 * See the COPYRIGHT.txt file distributed with this work for information
4 * regarding copyright ownership. Some portions may be licensed
5 * to Red Hat, Inc. under one or more contributor license agreements.
6 * See the AUTHORS.txt file in the distribution for a full listing of
7 * individual contributors.
8 *
9 * ModeShape is free software. Unless otherwise indicated, all code in ModeShape
10 * is licensed to you under the terms of the GNU Lesser General Public License as
11 * published by the Free Software Foundation; either version 2.1 of
12 * the License, or (at your option) any later version.
13 *
14 * ModeShape is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with this software; if not, write to the Free
21 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
22 * 02110-1301 USA, or see the FSF site: http://www.fsf.org.
23 */
24 package org.modeshape.graph.query.process;
25
26 import java.util.ArrayList;
27 import java.util.List;
28 import org.modeshape.graph.query.QueryContext;
29 import org.modeshape.graph.query.QueryResults.Columns;
30 import org.modeshape.graph.query.plan.PlanNode.Type;
31
32 /**
33 * A {@link ProcessingComponent} that executes a {@link Type#DEPENDENT_QUERY dependent query} node by first executing the left
34 * component and then executing the right component. If a variable name is specified, this component will save the query results
35 * from the the corresponding component into the {@link QueryContext#getVariables() variables} in the {@link QueryContext}.
36 */
37 public class DependentQueryComponent extends ProcessingComponent {
38
39 private final ProcessingComponent left;
40 private final ProcessingComponent right;
41 private final String leftVariableName;
42 private final String rightVariableName;
43
44 public DependentQueryComponent( QueryContext context,
45 ProcessingComponent left,
46 ProcessingComponent right,
47 String leftVariableName,
48 String rightVariableName ) {
49 super(context, right.getColumns());
50 this.left = left;
51 this.right = right;
52 this.leftVariableName = leftVariableName;
53 this.rightVariableName = rightVariableName;
54 }
55
56 /**
57 * Get the processing component that serves as the left side of the join.
58 *
59 * @return the left-side processing component; never null
60 */
61 protected final ProcessingComponent left() {
62 return left;
63 }
64
65 /**
66 * Get the processing component that serves as the right side of the join.
67 *
68 * @return the right-side processing component; never null
69 */
70 protected final ProcessingComponent right() {
71 return right;
72 }
73
74 /**
75 * Get the columns definition for the results from the left, independent query that is processed first.
76 *
77 * @return the left-side columns; never null
78 */
79 protected final Columns colunnsOfIndependentQuery() {
80 return left.getColumns();
81 }
82
83 /**
84 * Get the columns definition for the results from the right component that is dependent upon the left.
85 *
86 * @return the right-side columns; never null
87 */
88 protected final Columns colunnsOfDependentQuery() {
89 return right.getColumns();
90 }
91
92 /**
93 * {@inheritDoc}
94 *
95 * @see org.modeshape.graph.query.process.ProcessingComponent#execute()
96 */
97 @Override
98 public List<Object[]> execute() {
99 // First execute the left side ...
100 List<Object[]> leftResults = left.execute();
101 if (left.getColumns().getColumnCount() > 0) {
102 saveResultsToVariable(leftResults, leftVariableName);
103 }
104
105 // Then execute the right side ...
106 List<Object[]> rightResults = right.execute();
107 if (right.getColumns().getColumnCount() > 0) {
108 saveResultsToVariable(rightResults, rightVariableName);
109 }
110 return rightResults;
111 }
112
113 protected void saveResultsToVariable( List<Object[]> results,
114 String variableName ) {
115 if (results == null || results.isEmpty()) return;
116 if (variableName == null) return;
117
118 // Grab the first value in each of the tuples, and set on the query context ...
119 List<Object> singleColumnResults = new ArrayList<Object>(results.size());
120 // Make sure there is at least one column (in the first record; remaining tuples should be the same) ...
121 Object[] firstTuple = results.get(0);
122 if (firstTuple.length != 0) {
123 for (Object[] tuple : results) {
124 singleColumnResults.add(tuple[0]);
125 }
126 }
127 // Place the single column results into the variable ...
128 getContext().getVariables().put(variableName, singleColumnResults);
129 }
130 }