| /* |
| |
| 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.error.StandardException; |
| import org.apache.derby.iapi.reference.ClassName; |
| import org.apache.derby.iapi.services.context.ContextService; |
| import org.apache.derby.shared.common.sanity.SanityManager; |
| import org.apache.derby.iapi.sql.compile.CompilerContext; |
| import org.apache.derby.iapi.sql.compile.TypeCompiler; |
| import org.apache.derby.iapi.sql.compile.TypeCompilerFactory; |
| import org.apache.derby.iapi.types.DataTypeDescriptor; |
| import org.apache.derby.iapi.types.TypeId; |
| |
| /** |
| * Definition for the SUM()/AVG() aggregates. |
| * |
| */ |
| 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) |
| QueryTreeNode.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. |
| */ |
| final void setSumOrAvg(boolean isSum) |
| { |
| this.isSum = isSum; |
| } |
| |
| } |