/* This file is part of VoltDB.
* Copyright (C) 2008-2010 VoltDB L.L.C.
*
* VoltDB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* VoltDB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with VoltDB. If not, see <http://www.gnu.org/licenses/>.
*/
package org.voltdb.expressions;
import org.json.JSONException;
import org.json.JSONObject;
import org.voltdb.VoltType;
import org.voltdb.catalog.Database;
import org.voltdb.types.ExpressionType;
/**
*
*/
public class NullValueExpression extends AbstractValueExpression {
public NullValueExpression() {
super(ExpressionType.VALUE_NULL);
setValueType(VoltType.NULL);
}
@Override
public Object clone() throws CloneNotSupportedException {
NullValueExpression clone = (NullValueExpression)super.clone();
return clone;
}
@Override
public void validate() throws Exception {
super.validate();
//
// The output type must always be null!
//
if (m_valueType != VoltType.NULL) {
throw new Exception("ERROR: The output ValueType for '" + this + "' is '" + m_valueType + "'");
}
}
@Override
public boolean equals(Object obj) {
if (obj instanceof NullValueExpression == false) return false;
// if all seems well, defer to the superclass, which checks kids
return super.equals(obj);
}
@Override
protected void loadFromJSONObject(JSONObject obj, Database db) throws JSONException {}
}