/*
Derby - Class org.apache.derby.impl.sql.compile.SumAvgAggregateDefinition
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.context.ContextService;
import org.apache.derby.iapi.services.sanity.SanityManager;
import org.apache.derby.impl.sql.execute.SumAggregator;
import org.apache.derby.impl.sql.execute.AvgAggregator;
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.sql.compile.TypeCompiler;
import org.apache.derby.iapi.sql.compile.TypeCompilerFactory;
import org.apache.derby.iapi.sql.compile.CompilerContext;
import org.apache.derby.iapi.error.StandardException;
import org.apache.derby.iapi.reference.ClassName;
/**
* Defintion for the SUM()/AVG() aggregates.
*
*/
public class SumAvgAggregateDefinition
implements AggregateDefinition
{
private boolean isSum;
/**
* Niladic constructor. Does nothing. For ease
* Of use, only.
*/
public SumAvgAggregateDefinition() { 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 plus(). In which
* case avg() would need 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)
{
try
{
TypeId compType = inputType.getTypeId();
CompilerContext cc = (CompilerContext)
ContextService.getContext(CompilerContext.CONTEXT_ID);
TypeCompilerFactory tcf = cc.getTypeCompilerFactory();
TypeCompiler tc = tcf.getTypeCompiler(compType);
/*
** If the class implements NumberDataValue, then we
** are in business. Return type is same as input
** type.
*/
if (compType.isNumericTypeId())
{
aggregatorClass.append(getAggregatorClassName());
DataTypeDescriptor outDts = tc.resolveArithmeticOperation(
inputType, inputType, getOperator());
/*
** SUM and AVG may return null
*/
return outDts.getNullabilityType(true);
}
}
catch (StandardException e)
{
if (SanityManager.DEBUG)
{
SanityManager.THROWASSERT("Unexpected exception", e);
}
}
return null;
}
/**
* Return the aggregator class.
*
* @return SumAggregator.CLASS_NAME/AvgAggregator.CLASS_NAME
*/
private String getAggregatorClassName()
{
if ( isSum )
return ClassName.SumAggregator;
else
return ClassName.AvgAggregator;
}
/**
* Return the arithmetic operator corresponding
* to this operation.
*
* @return TypeCompiler.SUM_OP /TypeCompiler.AVG_OP
*/
protected String getOperator()
{
if ( isSum )
return TypeCompiler.SUM_OP;
else
return TypeCompiler.AVG_OP;
}
/**
* This is set by the parser.
*/
public final void setSumOrAvg(boolean isSum)
{
this.isSum = isSum;
}
}