org.apache.derby.impl.sql.execute

Class AggregatorInfo

java.lang.Object

org.apache.derby.impl.sql.execute.AggregatorInfo

All Implemented Interfaces:

java.io.Externalizable, java.io.Serializable, Formatable, TypedFormat

public class AggregatorInfo
extends java.lang.Object
implements Formatable

This is a simple class used to store the run time information needed to invoke an aggregator. This class is serializable because it is stored with the plan. It is serializable rather than externalizable because it isn't particularly complicated and presumbably we don't need version control on plans.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
AggregatorInfo() Niladic constructor for Formattable
AggregatorInfo(java.lang.String aggregateName, java.lang.String aggregatorClassName, int inputColNum, int outputColNum, int aggregatorColNum, boolean isDistinct, ResultDescription rd) Consructor

Method Summary

Modifier and Type	Method and Description
java.lang.String	getAggregateName() Get the name of the aggergate (e.g.
java.lang.String	getAggregatorClassName() Get the name of the class that implements the user aggregator for this class.
int	getAggregatorColNum() Get the column number for the aggregator column.
int	getInputColNum() Get the column number for the input (addend) column.
int	getOutputColNum() Get the column number for the output (result) column.
ResultDescription	getResultDescription() Get the result description for the input value to this aggregate.
int	getTypeFormatId() Get the formatID which corresponds to this class.
boolean	isDistinct() Is the aggergate distinct
void	readExternal(java.io.ObjectInput in) Read this object from a stream of stored objects.
java.lang.String	toString() Get a string for the object
void	writeExternal(java.io.ObjectOutput out) Write this object out

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

AggregatorInfo

public AggregatorInfo()

Niladic constructor for Formattable

AggregatorInfo

public AggregatorInfo(java.lang.String aggregateName,
                      java.lang.String aggregatorClassName,
                      int inputColNum,
                      int outputColNum,
                      int aggregatorColNum,
                      boolean isDistinct,
                      ResultDescription rd)

Consructor

Parameters:

aggregateName - the name of the aggregate. Not actually used anywhere except diagnostics. Should be the names as found in the language (e.g. MAX).

aggregatorClassName - the name of the aggregator used to process this aggregate. Aggregator expected to have a null arg constructor and implement Aggregator.

inputColNum - the input column number

outputColNum - the output column number

aggregatorColNum - the column number in which the aggregator is stored.

isDistinct - if it is a distinct aggregate

rd - the result description

Method Detail

getAggregateName

public java.lang.String getAggregateName()

Get the name of the aggergate (e.g. MAX)

Returns:

the aggeregate name

getAggregatorClassName

public java.lang.String getAggregatorClassName()

Get the name of the class that implements the user aggregator for this class.

Returns:

the aggeregator class name

getAggregatorColNum

public int getAggregatorColNum()

Get the column number for the aggregator column.

Returns:

the aggeregator colid

getInputColNum

public int getInputColNum()

Get the column number for the input (addend) column.

Returns:

the aggeregator colid

getOutputColNum

public int getOutputColNum()

Get the column number for the output (result) column.

Returns:

the aggeregator colid

isDistinct

public boolean isDistinct()

Is the aggergate distinct

Returns:

whether it is distinct

getResultDescription

public ResultDescription getResultDescription()

Get the result description for the input value to this aggregate.

Returns:

the rd

toString

public java.lang.String toString()

Get a string for the object

Overrides:

toString in class java.lang.Object

Returns:

string

writeExternal

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

Write this object out

Specified by:

writeExternal in interface java.io.Externalizable

Parameters:

out - write bytes here

Throws:

java.io.IOException - thrown on error

readExternal

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

Read this object from a stream of stored objects.

Specified by:

readExternal in interface java.io.Externalizable

Parameters:

in - read this.

Throws:

java.io.IOException - thrown on error

java.lang.ClassNotFoundException - thrown on error

getTypeFormatId

public int getTypeFormatId()

Get the formatID which corresponds to this class.

Specified by:

getTypeFormatId in interface TypedFormat

Returns:

the formatID of this class