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  void accumulate(DataValueDescriptor addend)      public  DataValueDescriptor getResult()      Return the result of the aggregation. public  int getTypeFormatId()      Get the formatID which corresponds to this class. public  void merge(ExecAggregator addend)      public  ExecAggregator newAggregator()      public  void readExternal(ObjectInput in)      public  void writeExternal(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)