org.apache.cassandra.db.aggregation

Class GroupMaker

java.lang.Object

org.apache.cassandra.db.aggregation.GroupMaker

public abstract class GroupMaker
extends java.lang.Object

A GroupMaker can be used to determine if some sorted rows belongs to the same group or not.

Field Summary

Fields

Modifier and Type	Field and Description
static GroupMaker	GROUP_EVERYTHING GroupMaker that groups all the rows together.

Constructor Summary

Constructors

Constructor and Description
GroupMaker()

Method Summary

Modifier and Type	Method and Description
abstract boolean	isNewGroup(DecoratedKey partitionKey, Clustering<?> clustering) Checks if a given row belongs to the same group that the previous row or not.
static GroupMaker	newInstance(ClusteringComparator comparator, int clusteringPrefixSize)
static GroupMaker	newInstance(ClusteringComparator comparator, int clusteringPrefixSize, GroupingState state)
boolean	returnAtLeastOneRow() Specify if at least one row must be returned.

Methods inherited from class java.lang.Object

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

Field Detail

GROUP_EVERYTHING

public static final GroupMaker GROUP_EVERYTHING

GroupMaker that groups all the rows together.

Constructor Detail

GroupMaker

public GroupMaker()

Method Detail

newInstance

public static GroupMaker newInstance(ClusteringComparator comparator,
                                     int clusteringPrefixSize,
                                     GroupingState state)

newInstance

public static GroupMaker newInstance(ClusteringComparator comparator,
                                     int clusteringPrefixSize)

isNewGroup

public abstract boolean isNewGroup(DecoratedKey partitionKey,
                                   Clustering<?> clustering)

Checks if a given row belongs to the same group that the previous row or not.

Parameters:

partitionKey - the partition key.

clustering - the row clustering key

Returns:

true if the row belongs to the same group that the previous one, false otherwise.

returnAtLeastOneRow

public boolean returnAtLeastOneRow()

Specify if at least one row must be returned. If the selection is performing some aggregations on all the rows, one row should be returned even if no records were processed.

Returns:

true if at least one row must be returned, false otherwise.