1 | /* |
2 | * Copyright 2004-2014 H2 Group. Multiple-Licensed under the MPL 2.0, |
3 | * and the EPL 1.0 (http://h2database.com/html/license.html). |
4 | * Initial Developer: H2 Group |
5 | */ |
6 | package org.h2.expression; |
7 | |
8 | import java.util.ArrayList; |
9 | |
10 | import org.h2.api.ErrorCode; |
11 | import org.h2.command.dml.Query; |
12 | import org.h2.engine.Session; |
13 | import org.h2.message.DbException; |
14 | import org.h2.result.ResultInterface; |
15 | import org.h2.table.ColumnResolver; |
16 | import org.h2.table.TableFilter; |
17 | import org.h2.value.Value; |
18 | import org.h2.value.ValueArray; |
19 | import org.h2.value.ValueNull; |
20 | |
21 | /** |
22 | * A query returning a single value. |
23 | * Subqueries are used inside other statements. |
24 | */ |
25 | public class Subquery extends Expression { |
26 | |
27 | private final Query query; |
28 | private Expression expression; |
29 | |
30 | public Subquery(Query query) { |
31 | this.query = query; |
32 | } |
33 | |
34 | @Override |
35 | public Value getValue(Session session) { |
36 | query.setSession(session); |
37 | ResultInterface result = query.query(2); |
38 | try { |
39 | int rowcount = result.getRowCount(); |
40 | if (rowcount > 1) { |
41 | throw DbException.get(ErrorCode.SCALAR_SUBQUERY_CONTAINS_MORE_THAN_ONE_ROW); |
42 | } |
43 | Value v; |
44 | if (rowcount <= 0) { |
45 | v = ValueNull.INSTANCE; |
46 | } else { |
47 | result.next(); |
48 | Value[] values = result.currentRow(); |
49 | if (result.getVisibleColumnCount() == 1) { |
50 | v = values[0]; |
51 | } else { |
52 | v = ValueArray.get(values); |
53 | } |
54 | } |
55 | return v; |
56 | } finally { |
57 | result.close(); |
58 | } |
59 | } |
60 | |
61 | @Override |
62 | public int getType() { |
63 | return getExpression().getType(); |
64 | } |
65 | |
66 | @Override |
67 | public void mapColumns(ColumnResolver resolver, int level) { |
68 | query.mapColumns(resolver, level + 1); |
69 | } |
70 | |
71 | @Override |
72 | public Expression optimize(Session session) { |
73 | query.prepare(); |
74 | return this; |
75 | } |
76 | |
77 | @Override |
78 | public void setEvaluatable(TableFilter tableFilter, boolean b) { |
79 | query.setEvaluatable(tableFilter, b); |
80 | } |
81 | |
82 | @Override |
83 | public int getScale() { |
84 | return getExpression().getScale(); |
85 | } |
86 | |
87 | @Override |
88 | public long getPrecision() { |
89 | return getExpression().getPrecision(); |
90 | } |
91 | |
92 | @Override |
93 | public int getDisplaySize() { |
94 | return getExpression().getDisplaySize(); |
95 | } |
96 | |
97 | @Override |
98 | public String getSQL() { |
99 | return "(" + query.getPlanSQL() + ")"; |
100 | } |
101 | |
102 | @Override |
103 | public void updateAggregate(Session session) { |
104 | query.updateAggregate(session); |
105 | } |
106 | |
107 | private Expression getExpression() { |
108 | if (expression == null) { |
109 | ArrayList<Expression> expressions = query.getExpressions(); |
110 | int columnCount = query.getColumnCount(); |
111 | if (columnCount == 1) { |
112 | expression = expressions.get(0); |
113 | } else { |
114 | Expression[] list = new Expression[columnCount]; |
115 | for (int i = 0; i < columnCount; i++) { |
116 | list[i] = expressions.get(i); |
117 | } |
118 | expression = new ExpressionList(list); |
119 | } |
120 | } |
121 | return expression; |
122 | } |
123 | |
124 | @Override |
125 | public boolean isEverything(ExpressionVisitor visitor) { |
126 | return query.isEverything(visitor); |
127 | } |
128 | |
129 | public Query getQuery() { |
130 | return query; |
131 | } |
132 | |
133 | @Override |
134 | public int getCost() { |
135 | return query.getCostAsExpression(); |
136 | } |
137 | |
138 | @Override |
139 | public Expression[] getExpressionColumns(Session session) { |
140 | return getExpression().getExpressionColumns(session); |
141 | } |
142 | } |