org.vanilladb.core.sql.aggfn

Class AggregationFn

java.lang.Object

org.vanilladb.core.sql.aggfn.AggregationFn

Direct Known Subclasses:

AvgFn, CountFn, DistinctCountFn, MaxFn, MinFn, SumFn

public abstract class AggregationFn
extends Object

The interface implemented by aggregation functions.

Note that the aggregation function should implement Object.hashCode() and Object.equals(Object) which are used to verify the equality of aggregation functions.

Constructor Summary

Constructors

Constructor and Description
AggregationFn()

Method Summary

Modifier and Type	Method and Description
abstract String	argumentFieldName() Returns the name of the argument field.
abstract boolean	equals(Object other) Returns a hash code value for the object.
abstract String	fieldName() Returns the name of the new aggregation field.
abstract Type	fieldType() Returns the type of aggregation value.
abstract int	hashCode() Returns a hash code value for the object.
abstract boolean	isArgumentTypeDependent() Returns true if the type of aggregation value is depend on the argument field.
abstract void	processFirst(Record rec) Processes the specified record by regarding it as the first record in a group.
abstract void	processNext(Record rec) Processes the specified record by regarding it as a following up record in a group.
abstract Constant	value() Returns the computed aggregation value given the records processed previously.

Methods inherited from class java.lang.Object

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

Constructor Detail

AggregationFn

public AggregationFn()

Method Detail

processFirst

public abstract void processFirst(Record rec)

Processes the specified record by regarding it as the first record in a group.

Parameters:

rec - a record to aggregate over.

processNext

public abstract void processNext(Record rec)

Processes the specified record by regarding it as a following up record in a group.

Parameters:

rec - a rec to aggregate over.

argumentFieldName

public abstract String argumentFieldName()

Returns the name of the argument field.

Returns:

the name of the argument field

fieldName

public abstract String fieldName()

Returns the name of the new aggregation field.

Returns:

the name of the new aggregation field

value

public abstract Constant value()

Returns the computed aggregation value given the records processed previously.

Returns:

the computed aggregation value

fieldType

public abstract Type fieldType()

Returns the type of aggregation value.

Returns:

the type of aggregation value

isArgumentTypeDependent

public abstract boolean isArgumentTypeDependent()

Returns true if the type of aggregation value is depend on the argument field.

Returns:

true if the type of aggregation value is depend on the argument field

hashCode

public abstract int hashCode()

Returns a hash code value for the object.

Overrides:

hashCode in class Object

equals

public abstract boolean equals(Object other)

Returns a hash code value for the object.

Overrides:

equals in class Object