simpledb

Class IntegerAggregator

java.lang.Object

simpledb.IntegerAggregator

All Implemented Interfaces:

java.io.Serializable, Aggregator

public class IntegerAggregator
extends java.lang.Object
implements Aggregator

Knows how to compute some aggregate over a set of IntFields.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
private class	IntegerAggregator.MyInteger

Nested classes/interfaces inherited from interface simpledb.Aggregator

Aggregator.Op, Aggregator.TupleMapIterator

Field Summary

Fields

Modifier and Type	Field and Description
private int	aField
private java.util.HashMap<Field,IntegerAggregator.MyInteger>	fieldResMap
private java.util.HashMap<Field,Tuple>	fieldTupleMap
private int	gbField
private Type	gbFieldType
private Tuple	noGroupTuple
private Aggregator.Op	op
private static long	serialVersionUID
private TupleDesc	tupleDesc

Fields inherited from interface simpledb.Aggregator

NO_GROUPING, noGroupField

Constructor Summary

Constructors

Constructor and Description
IntegerAggregator(int gbfield, Type gbfieldtype, int afield, Aggregator.Op what) Aggregate constructor

Method Summary

Modifier and Type	Method and Description
DbIterator	iterator() Create a DbIterator over group aggregate results.
void	mergeTupleIntoGroup(Tuple tup) Merge a new tuple into the aggregate, grouping as indicated in the constructor

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

private static final long serialVersionUID

See Also:

Constant Field Values

gbField

private int gbField

aField

private int aField

gbFieldType

private Type gbFieldType

op

private Aggregator.Op op

fieldTupleMap

private java.util.HashMap<Field,Tuple> fieldTupleMap

fieldResMap

private java.util.HashMap<Field,IntegerAggregator.MyInteger> fieldResMap

tupleDesc

private TupleDesc tupleDesc

noGroupTuple

private Tuple noGroupTuple

Constructor Detail

IntegerAggregator

public IntegerAggregator(int gbfield,
                         Type gbfieldtype,
                         int afield,
                         Aggregator.Op what)

Aggregate constructor

Parameters:

gbfield - the 0-based index of the group-by field in the tuple, or NO_GROUPING if there is no grouping

gbfieldtype - the type of the group by field (e.g., Type.INT_TYPE), or null if there is no grouping

afield - the 0-based index of the aggregate field in the tuple

what - the aggregation operator

Method Detail

mergeTupleIntoGroup

public void mergeTupleIntoGroup(Tuple tup)

Merge a new tuple into the aggregate, grouping as indicated in the constructor

Specified by:

mergeTupleIntoGroup in interface Aggregator

Parameters:

tup - the Tuple containing an aggregate field and a group-by field

iterator

public DbIterator iterator()

Create a DbIterator over group aggregate results.

Specified by:

iterator in interface Aggregator

Returns:

a DbIterator whose tuples are the pair (groupVal, aggregateVal) if using group, or a single (aggregateVal) if no grouping. The aggregateVal is determined by the type of aggregate specified in the constructor.

See Also:

for a possible helper