org.apache.druid.frame.key

Class ClusterBy

java.lang.Object

org.apache.druid.frame.key.ClusterBy

public class ClusterBy
extends Object

Describes a key used for sorting or partitioning. Keys have columns, and some of those columns may comprise a "bucket key". See getBucketByCount() for details about bucket keys.

Constructor Summary

Constructors

Constructor and Description
ClusterBy(List<SortColumn> columns, int bucketByCount)

Method Summary

Modifier and Type	Method and Description
Comparator<RowKey>	bucketComparator() Comparator that compares bucket keys for this instance.
Comparator<byte[]>	byteKeyComparator() Comparator that compares byte arrays of keys for this instance using the given signature directly.
boolean	equals(Object o)
int	getBucketByCount() How many fields from getColumns() comprise the "bucket key".
List<SortColumn>	getColumns() The columns that comprise this key, in order.
int	hashCode()
Comparator<RowKey>	keyComparator() Comparator that compares keys for this instance using the given signature.
RowKeyReader	keyReader(ColumnInspector inspector) Create a reader for keys for this instance.
static ClusterBy	none() Create an empty key.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

ClusterBy

public ClusterBy(List<SortColumn> columns,
                 int bucketByCount)

Method Detail

none

public static ClusterBy none()

Create an empty key.

getColumns

public List<SortColumn> getColumns()

The columns that comprise this key, in order.

getBucketByCount

public int getBucketByCount()

How many fields from getColumns() comprise the "bucket key". Bucketing is like strict partitioning: all rows in a given partition will have the exact same bucket key. It is most commonly used to implement segment granularity during ingestion. The bucket key is a prefix of the complete key. Will always be less than, or equal to, the size of getColumns(). Not relevant when a ClusterBy instance is used as an ordering key rather than a partitioning key.

keyReader

public RowKeyReader keyReader(ColumnInspector inspector)

Create a reader for keys for this instance. The provided ColumnInspector is used to determine the types of fields in the keys. The provided signature does not have to exactly match the sortColumns: it merely has to contain them all.

keyComparator

public Comparator<RowKey> keyComparator()

Comparator that compares keys for this instance using the given signature.

byteKeyComparator

public Comparator<byte[]> byteKeyComparator()

Comparator that compares byte arrays of keys for this instance using the given signature directly.

bucketComparator

public Comparator<RowKey> bucketComparator()

Comparator that compares bucket keys for this instance. Bucket keys are retrieved by calling RowKeyReader.trim(RowKey, int) with getBucketByCount().

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object