simpledb.materialize
Interface AggregationFn

All Known Implementing Classes:

CountFn, MaxFn

public interface AggregationFn

The interface implemented by aggregation functions. Aggregation functions are used by the groupby operator.

Author:

Edward Sciore

Method Summary

String	fieldName() Returns the name of the new aggregation field.
void	processFirst(Scan s) Uses the current record of the specified scan to be the first record in the group.
void	processNext(Scan s) Uses the current record of the specified scan to be the next record in the group.
Constant	value() Returns the computed aggregation value.

Method Detail

processFirst

void processFirst(Scan s)

Uses the current record of the specified scan to be the first record in the group.

Parameters:

s - the scan to aggregate over.

processNext

void processNext(Scan s)

Uses the current record of the specified scan to be the next record in the group.

Parameters:

s - the scan to aggregate over.

fieldName

String fieldName()

Returns the name of the new aggregation field.

Returns:

the name of the new aggregation field

value

Constant value()

Returns the computed aggregation value.

Returns:

the computed aggregation value