?? conditionexists.java
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/*
* Copyright 2004-2008 H2 Group. Licensed under the H2 License, Version 1.0
* (http://h2database.com/html/license.html).
* Initial Developer: H2 Group
*/
package org.h2.expression;
import java.sql.SQLException;
import org.h2.command.dml.Query;
import org.h2.engine.Session;
import org.h2.result.LocalResult;
import org.h2.table.ColumnResolver;
import org.h2.table.TableFilter;
import org.h2.value.Value;
import org.h2.value.ValueBoolean;
/**
* An 'exists' condition as in WHERE EXISTS(SELECT ...)
*/
public class ConditionExists extends Condition {
private final Query query;
public ConditionExists(Query query) {
this.query = query;
}
public Value getValue(Session session) throws SQLException {
query.setSession(session);
LocalResult result = query.query(1);
session.addTemporaryResult(result);
boolean r = result.getRowCount() > 0;
return ValueBoolean.get(r);
}
public Expression optimize(Session session) throws SQLException {
query.prepare();
return this;
}
public String getSQL() {
StringBuffer buff = new StringBuffer();
buff.append("EXISTS(");
buff.append(query.getPlanSQL());
buff.append(")");
return buff.toString();
}
public void updateAggregate(Session session) {
// TODO exists: is it allowed that the subquery contains aggregates?
// probably not
// select id from test group by id having exists (select * from test2
// where id=count(test.id))
}
public void mapColumns(ColumnResolver resolver, int level) throws SQLException {
query.mapColumns(resolver, level + 1);
}
public void setEvaluatable(TableFilter tableFilter, boolean b) {
query.setEvaluatable(tableFilter, b);
}
public boolean isEverything(ExpressionVisitor visitor) {
return query.isEverything(visitor);
}
public int getCost() {
return 10 + (int) (10 * query.getCost());
}
}
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