Field Detail

• isMax

  private boolean isMax

Constructor Detail

• MaxMinAggregator

  public MaxMinAggregator()

Method Detail

• setup

  public void setup​(ClassFactory cf,
                    java.lang.String aggregateName,
                    DataTypeDescriptor returnType)

  Description copied from interface: ExecAggregator
  Set's up the aggregate for processing.

  Specified by:

  setup in interface ExecAggregator

  Overrides:

  setup in class OrderableAggregator

  Parameters:

  cf - Database-specific class factory.

  aggregateName - For builtin aggregates, this is a SQL aggregate name like MAX. For user-defined aggregates, this is the name of the user-written class which implements org.apache.derby.agg.Aggregator.

  returnType - The type returned by the getResult() method.

• accumulate

  protected void accumulate​(DataValueDescriptor addend)
                     throws StandardException

  Accumulate

  Specified by:

  accumulate in class SystemAggregator

  Parameters:

  addend - value to be added in

  Throws:

  StandardException - on error

• newAggregator

  public ExecAggregator newAggregator()

  Description copied from interface: ExecAggregator
  Return a new initialized copy of this aggregator, any state set by the setup() method of the original Aggregator must be copied into the new aggregator.

  Returns:

  ExecAggregator the new aggregator

• writeExternal

  public void writeExternal​(java.io.ObjectOutput out)
                     throws java.io.IOException

  Description copied from class: OrderableAggregator
  Although we are not expected to be persistent per se, we may be written out by the sorter temporarily. So we need to be able to write ourselves out and read ourselves back in. We rely on formatable to handle situations where value is null.

  Why would we be called to write ourselves out if we are null? For scalar aggregates, we don't bother setting up the aggregator since we only need a single row. So for a scalar aggregate that needs to go to disk, the aggregator might be null.

  Specified by:

  writeExternal in interface java.io.Externalizable

  Overrides:

  writeExternal in class OrderableAggregator

  Throws:

  java.io.IOException - on error

  See Also:

  Externalizable.writeExternal(java.io.ObjectOutput)

• readExternal

  public void readExternal​(java.io.ObjectInput in)
                    throws java.io.IOException,
                           java.lang.ClassNotFoundException

  Specified by:

  readExternal in interface java.io.Externalizable

  Overrides:

  readExternal in class OrderableAggregator

  Throws:

  java.io.IOException - on error

  java.lang.ClassNotFoundException - on error

  See Also:

  Externalizable.readExternal(java.io.ObjectInput)

• getTypeFormatId

  public int getTypeFormatId()

  Get the formatID which corresponds to this class.

  Returns:

  the formatID of this class