Java Doc for AvgAggregator.java in  » Database-DBMS » db-derby-10.2 » org » apache » derby » impl » sql » execute » Java Source Code / Java DocumentationJava Source Code and Java Documentation

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Java Source Code / Java Documentation » Database DBMS » db derby 10.2 » org.apache.derby.impl.sql.execute 
Source Cross Reference  Class Diagram Java Document (Java Doc) 


java.lang.Object
   org.apache.derby.impl.sql.execute.SystemAggregator
      org.apache.derby.impl.sql.execute.OrderableAggregator
         org.apache.derby.impl.sql.execute.SumAggregator
            org.apache.derby.impl.sql.execute.AvgAggregator

AvgAggregator
final public class AvgAggregator extends SumAggregator (Code)
Aggregator for AVG(). Extends the SumAggregator and implements a count. Result is then sum()/count(). To handle overflow we catch the exception for value out of range, then we swap the holder for the current sum to one that can handle a larger range. Eventually a sum may end up in a SQLDecimal which can handle an infinite range. Once this type promotion has happened, it will not revert back to the original type, even if the sum would fit in a lesser type.




Method Summary
protected  voidaccumulate(DataValueDescriptor addend)
    
public  DataValueDescriptorgetResult()
     Return the result of the aggregation.
public  intgetTypeFormatId()
     Get the formatID which corresponds to this class.
public  voidmerge(ExecAggregator addend)
    
public  ExecAggregatornewAggregator()
    
public  voidreadExternal(ObjectInput in)
    
public  voidwriteExternal(ObjectOutput out)
    



Method Detail
accumulate
protected void accumulate(DataValueDescriptor addend) throws StandardException(Code)



getResult
public DataValueDescriptor getResult() throws StandardException(Code)
Return the result of the aggregation. If the count is zero, then we haven't averaged anything yet, so we return null. Otherwise, return the running average as a double. null or the average as Double



getTypeFormatId
public int getTypeFormatId()(Code)
Get the formatID which corresponds to this class. the formatID of this class



merge
public void merge(ExecAggregator addend) throws StandardException(Code)



newAggregator
public ExecAggregator newAggregator()(Code)



readExternal
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException(Code)

See Also:   java.io.Externalizable.readExternal
See Also:   
exception:
  IOException - on error



writeExternal
public void writeExternal(ObjectOutput out) throws IOException(Code)

exception:
  IOException - on error



Methods inherited from org.apache.derby.impl.sql.execute.SumAggregator
protected void accumulate(DataValueDescriptor addend) throws StandardException(Code)(Java Doc)
public int getTypeFormatId()(Code)(Java Doc)
public ExecAggregator newAggregator()(Code)(Java Doc)

Fields inherited from org.apache.derby.impl.sql.execute.OrderableAggregator
protected DataValueDescriptor value(Code)(Java Doc)

Methods inherited from org.apache.derby.impl.sql.execute.OrderableAggregator
public DataValueDescriptor getResult() throws StandardException(Code)(Java Doc)
public void merge(ExecAggregator addend) throws StandardException(Code)(Java Doc)
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException(Code)(Java Doc)
public void setup(String aggregateName)(Code)(Java Doc)
public void writeExternal(ObjectOutput out) throws IOException(Code)(Java Doc)

Methods inherited from org.apache.derby.impl.sql.execute.SystemAggregator
public void accumulate(DataValueDescriptor addend, Object ga) throws StandardException(Code)(Java Doc)
abstract protected void accumulate(DataValueDescriptor addend) throws StandardException(Code)(Java Doc)
public boolean didEliminateNulls()(Code)(Java Doc)
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException(Code)(Java Doc)
public void writeExternal(ObjectOutput out) throws IOException(Code)(Java Doc)

Methods inherited from java.lang.Object
native protected Object clone() throws CloneNotSupportedException(Code)(Java Doc)
public boolean equals(Object obj)(Code)(Java Doc)
protected void finalize() throws Throwable(Code)(Java Doc)
final native public Class getClass()(Code)(Java Doc)
native public int hashCode()(Code)(Java Doc)
final native public void notify()(Code)(Java Doc)
final native public void notifyAll()(Code)(Java Doc)
public String toString()(Code)(Java Doc)
final native public void wait(long timeout) throws InterruptedException(Code)(Java Doc)
final public void wait(long timeout, int nanos) throws InterruptedException(Code)(Java Doc)
final public void wait() throws InterruptedException(Code)(Java Doc)

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