/*
* Copyright 2004-2011 H2 Group. Multiple-Licensed under the H2 License,
* Version 1.0, and under the Eclipse Public License, Version 1.0
* (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.expression;
import java.util.ArrayList;
import org.h2.command.dml.Query;
import org.h2.constant.ErrorCode;
import org.h2.engine.Session;
import org.h2.message.DbException;
import org.h2.result.ResultInterface;
import org.h2.table.ColumnResolver;
import org.h2.table.TableFilter;
import org.h2.value.Value;
import org.h2.value.ValueArray;
import org.h2.value.ValueNull;
/**
* A query returning a single value.
* Subqueries are used inside other statements.
*/
public class Subquery extends Expression {
private Query query;
private Expression expression;
public Subquery(Query query) {
this.query = query;
}
public Value getValue(Session session) {
query.setSession(session);
ResultInterface result = query.query(2);
try {
int rowcount = result.getRowCount();
if (rowcount > 1) {
throw DbException.get(ErrorCode.SCALAR_SUBQUERY_CONTAINS_MORE_THAN_ONE_ROW);
}
Value v;
if (rowcount <= 0) {
v = ValueNull.INSTANCE;
} else {
result.next();
Value[] values = result.currentRow();
if (result.getVisibleColumnCount() == 1) {
v = values[0];
} else {
v = ValueArray.get(values);
}
}
return v;
} finally {
result.close();
}
}
public int getType() {
return getExpression().getType();
}
public void mapColumns(ColumnResolver resolver, int level) {
query.mapColumns(resolver, level + 1);
}
public Expression optimize(Session session) {
query.prepare();
return this;
}
public void setEvaluatable(TableFilter tableFilter, boolean b) {
query.setEvaluatable(tableFilter, b);
}
public int getScale() {
return getExpression().getScale();
}
public long getPrecision() {
return getExpression().getPrecision();
}
public int getDisplaySize() {
return getExpression().getDisplaySize();
}
public String getSQL() {
return "(" + query.getPlanSQL() + ")";
}
public void updateAggregate(Session session) {
query.updateAggregate(session);
}
private Expression getExpression() {
if (expression == null) {
ArrayList<Expression> expressions = query.getExpressions();
int columnCount = query.getColumnCount();
if (columnCount == 1) {
expression = expressions.get(0);
} else {
Expression[] list = new Expression[columnCount];
for (int i = 0; i < columnCount; i++) {
list[i] = expressions.get(i);
}
expression = new ExpressionList(list);
}
}
return expression;
}
public boolean isEverything(ExpressionVisitor visitor) {
return query.isEverything(visitor);
}
public Query getQuery() {
return query;
}
public int getCost() {
return query.getCostAsExpression();
}
public Expression[] getExpressionColumns(Session session) {
return getExpression().getExpressionColumns(session);
}
}