simpledb.materialize
Class MaxFn

java.lang.Object
  simpledb.materialize.MaxFn

All Implemented Interfaces:

AggregationFn

public class MaxFn
extends java.lang.Object
implements AggregationFn

The max aggregation function.

Author:

Edward Sciore

Constructor Summary

MaxFn(java.lang.String fldname)
Creates a max aggregation function for the specified field.

Method Summary

java.lang.String	fieldName() Returns the field's name, prepended by "maxof".
void	processFirst(Scan s) Starts a new maximum to be the field value in the current record.
void	processNext(Scan s) Replaces the current maximum by the field value in the current record, if it is higher.
Constant	value() Returns the current maximum.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

MaxFn

public MaxFn(java.lang.String fldname)

Creates a max aggregation function for the specified field.

Parameters:

fldname - the name of the aggregated field

Method Detail

processFirst

public void processFirst(Scan s)

Starts a new maximum to be the field value in the current record.

Specified by:

processFirst in interface AggregationFn

Parameters:

s - the scan to aggregate over.

See Also:

AggregationFn.processFirst(simpledb.query.Scan)

processNext

public void processNext(Scan s)

Replaces the current maximum by the field value in the current record, if it is higher.

Specified by:

processNext in interface AggregationFn

Parameters:

s - the scan to aggregate over.

See Also:

AggregationFn.processNext(simpledb.query.Scan)

fieldName

public java.lang.String fieldName()

Returns the field's name, prepended by "maxof".

Specified by:

fieldName in interface AggregationFn

Returns:

the name of the new aggregation field

See Also:

AggregationFn.fieldName()

value

public Constant value()

Returns the current maximum.

Specified by:

value in interface AggregationFn

Returns:

the computed aggregation value

See Also:

AggregationFn.value()