/*
Derby - Class org.apache.derby.impl.sql.compile.MaxMinAggregateDefinition
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to you under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/
package org.apache.derby.impl.sql.compile;
import org.apache.derby.iapi.sql.conn.LanguageConnectionContext;
import org.apache.derby.iapi.services.sanity.SanityManager;
import org.apache.derby.impl.sql.execute.MaxMinAggregator;
import org.apache.derby.catalog.TypeDescriptor;
import org.apache.derby.iapi.types.TypeId;
import org.apache.derby.iapi.types.DataTypeDescriptor;
import org.apache.derby.iapi.types.NumberDataValue;
import org.apache.derby.iapi.error.StandardException;
import org.apache.derby.iapi.services.context.ContextService;
import org.apache.derby.iapi.reference.ClassName;
/**
* Defintion for the MAX()/MIN() aggregates.
*
*/
public class MaxMinAggregateDefinition
implements AggregateDefinition
{
private boolean isMax;
/**
* Niladic constructor. Does nothing. For ease
* Of use, only.
*/
public MaxMinAggregateDefinition() { super(); }
/**
* Determines the result datatype. Accept NumberDataValues
* only.
* <P>
* <I>Note</I>: In the future you should be able to do
* a sum user data types. One option would be to run
* sum on anything that implements divide().
*
* @param inputType the input type, either a user type or a java.lang object
*
* @return the output Class (null if cannot operate on
* value expression of this type.
*/
public final DataTypeDescriptor getAggregator(DataTypeDescriptor inputType,
StringBuffer aggregatorClass)
{
LanguageConnectionContext lcc = (LanguageConnectionContext)
ContextService.getContext(LanguageConnectionContext.CONTEXT_ID);
/*
** MIN and MAX may return null
*/
DataTypeDescriptor dts = inputType.getNullabilityType(true);
TypeId compType = dts.getTypeId();
/*
** If the class implements NumberDataValue, then we
** are in business. Return type is same as input
** type.
*/
if (compType.orderable(
lcc.getLanguageConnectionFactory().getClassFactory()))
{
aggregatorClass.append(ClassName.MaxMinAggregator);
return dts;
}
return null;
}
/**
* This is set by the parser.
*/
public final void setMaxOrMin(boolean isMax)
{
this.isMax = isMax;
}
/**
* Return if the aggregator class is for min/max.
*
* @return boolean true/false
*/
public final boolean isMax()
{
return(isMax);
}
}