org.vanilladb.core.sql.aggfn

Class CountFn

java.lang.Object

org.vanilladb.core.sql.aggfn.AggregationFn

org.vanilladb.core.sql.aggfn.CountFn

public class CountFn
extends AggregationFn

The count aggregation function.

Constructor Summary

Constructors

Constructor and Description
CountFn(String fldName)

Method Summary

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

CountFn

public CountFn(String fldName)

Method Detail

processFirst

public void processFirst(Record rec)

Description copied from class: AggregationFn

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

Specified by:

processFirst in class AggregationFn

Parameters:

rec - a record to aggregate over.

processNext

public void processNext(Record rec)

Description copied from class: AggregationFn

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

Specified by:

processNext in class AggregationFn

Parameters:

rec - a rec to aggregate over.

argumentFieldName

public String argumentFieldName()

Description copied from class: AggregationFn

Returns the name of the argument field.

Specified by:

argumentFieldName in class AggregationFn

Returns:

the name of the argument field

fieldName

public String fieldName()

Description copied from class: AggregationFn

Returns the name of the new aggregation field.

Specified by:

fieldName in class AggregationFn

Returns:

the name of the new aggregation field

value

public Constant value()

Description copied from class: AggregationFn

Returns the computed aggregation value given the records processed previously.

Specified by:

value in class AggregationFn

Returns:

the computed aggregation value

fieldType

public Type fieldType()

Description copied from class: AggregationFn

Returns the type of aggregation value.

Specified by:

fieldType in class AggregationFn

Returns:

the type of aggregation value

isArgumentTypeDependent

public boolean isArgumentTypeDependent()

Description copied from class: AggregationFn

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

Specified by:

isArgumentTypeDependent in class AggregationFn

Returns:

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

hashCode

public int hashCode()

Description copied from class: AggregationFn

Returns a hash code value for the object.

Specified by:

hashCode in class AggregationFn

equals

public boolean equals(Object other)

Description copied from class: AggregationFn

Returns a hash code value for the object.

Specified by:

equals in class AggregationFn