com.pervasive.datarush.ports.record

Class KeyDrivenDataDistribution

java.lang.Object

com.pervasive.datarush.ports.record.DataDistribution

com.pervasive.datarush.ports.record.PartialDataDistribution

com.pervasive.datarush.ports.record.PartialStaticDataDistribution

com.pervasive.datarush.ports.record.KeyDrivenDataDistribution

public final class KeyDrivenDataDistribution
extends PartialStaticDataDistribution

DataDistribution based on a set of keys from the input data. A KeyDrivenDataDistribution selects a set of keys, applying the specified base partitioning function to that set of keys. The function must be a function of input. This guarantees that data with rows with equivalent keys are located in the same partition.

Method Summary

Modifier and Type	Method and Description
AliasSet[]	getAliases() Returns the fields that are referenced by this distribution.
PartitioningFunction	getBasePartitionFunction() Returns the base partitioning function.
String[]	getKeys() Returns the keys by which we are partitioned.
protected PartitioningFunction	getPartitioningFunction() Subclasses must override this method to provide the partitioning function to be used
static KeyDrivenDataDistribution	hashed(List<String> keys) Returns a distribution that distributes based on a hashcode of the named key fields.
static KeyDrivenDataDistribution	hashed(String... keys) Returns a distribution that distributes based on a hashcode of the named key fields.
boolean	isGroupedBy(String[] keys) Returns true if this distribution guarantees groupings on the specified list of keys will not be split across partitions.
boolean	isGroupingCompatible(String[] keys) Returns true if this distribution guarantees groupings on the specified list of keys will not be split across partitions.
boolean	isLocal()
static KeyDrivenDataDistribution	keyed(PartitioningFunction basePartitionFunction, List<String> keys) Returns a distribution that distributes based on the given function of the named key fields.
static KeyDrivenDataDistribution	keyed(PartitioningFunction basePartitionFunction, String... keys) Returns a distribution that distributes based on the given function of the named key fields.
static KeyDrivenDataDistribution	localKeyed(PartitioningFunction basePartitionFunction, List<String> keys) For advanced use only; this redistributes per-JVM but not across the cluster.
static KeyDrivenDataDistribution	ranges(List<RecordToken> boundaries) Returns a distribution that distributes based on specified range boundaries
PartialDataDistribution	remap(FieldRemapping mapping) Applies the given field remapping to this distribution, changing names as required.
protected boolean	requiresRepartitionFrom(PartialDataDistribution source) Subclasses must override this method to declare whether a repartition is required given the source distribution.
protected boolean	supportsLocalRepartition() Subclasses may override to indicate that they support a local repartition
String	toString()

Methods inherited from class com.pervasive.datarush.ports.record.PartialDataDistribution

getGatherScheme

Methods inherited from class java.lang.Object

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

Method Detail

hashed

public static KeyDrivenDataDistribution hashed(String... keys)

Returns a distribution that distributes based on a hashcode of the named key fields.

Parameters:

keys - the names of the key fields

Returns:

a hash distribution

hashed

public static KeyDrivenDataDistribution hashed(List<String> keys)

Returns a distribution that distributes based on a hashcode of the named key fields.

Parameters:

keys - the names of the key fields

Returns:

a hash distribution

ranges

public static KeyDrivenDataDistribution ranges(List<RecordToken> boundaries)

Returns a distribution that distributes based on specified range boundaries

Parameters:

boundaries - the range boundaries

Returns:

a range distribution

keyed

public static KeyDrivenDataDistribution keyed(PartitioningFunction basePartitionFunction,
                                              String... keys)

Returns a distribution that distributes based on the given function of the named key fields.

Parameters:

basePartitionFunction - the partition function

keys - the names of the key fields

Returns:

a key driven distribution

Throws:

IllegalArgumentException - if the provided function is not a function of input

keyed

public static KeyDrivenDataDistribution keyed(PartitioningFunction basePartitionFunction,
                                              List<String> keys)
                                       throws IllegalArgumentException

Returns a distribution that distributes based on the given function of the named key fields.

Parameters:

basePartitionFunction - the partition function

keys - the names of the key fields

Returns:

a key driven distribution

Throws:

IllegalArgumentException - if the provided function is not a function of input

localKeyed

public static KeyDrivenDataDistribution localKeyed(PartitioningFunction basePartitionFunction,
                                                   List<String> keys)
                                            throws IllegalArgumentException

For advanced use only; this redistributes per-JVM but not across the cluster. This is not a general-purpose partitioning strategy but can be used in certain cases where there is a performance benefit to locally repartitioning data.

Returns a distribution that locally distributes based on the given function of the named key fields.

Parameters:

basePartitionFunction - the partition function

keys - the names of the key fields

Returns:

a key driven distribution

Throws:

IllegalArgumentException - if the provided function is not a function of input

getBasePartitionFunction

public PartitioningFunction getBasePartitionFunction()

Returns the base partitioning function. This function is applied to a record consisting of the selected key fields.

Returns:

the base partitioning function

isLocal

public boolean isLocal()

isGroupedBy

public boolean isGroupedBy(String[] keys)

Returns true if this distribution guarantees groupings on the specified list of keys will not be split across partitions.

Parameters:

keys - the group keys

Returns:

whether this distribution preserves groupings across partitions

isGroupingCompatible

public boolean isGroupingCompatible(String[] keys)

Returns true if this distribution guarantees groupings on the specified list of keys will not be split across partitions.

Parameters:

keys - the group keys

Returns:

whether this distribution preserves groupings across partitions

requiresRepartitionFrom

protected boolean requiresRepartitionFrom(PartialDataDistribution source)

Description copied from class: PartialStaticDataDistribution

Subclasses must override this method to declare whether a repartition is required given the source distribution. Implementations may err on the side of caution by always returning true but this may have an impact on performance.

Specified by:

requiresRepartitionFrom in class PartialStaticDataDistribution

Parameters:

source - the source distribution

Returns:

true if a repartition is required, false if this data distribution matches what was specified.

toString

public String toString()

Specified by:

toString in class DataDistribution

getKeys

public String[] getKeys()

Returns the keys by which we are partitioned.

Returns:

the keys by which we are partitioned.

remap

public PartialDataDistribution remap(FieldRemapping mapping)

Applies the given field remapping to this distribution, changing names as required. If any hash keys refer to columns that are dropped as part of the rename, the result is an UnspecifiedPartialDistribution.

Specified by:

remap in class DataDistribution

Parameters:

mapping - the field remapping.

Returns:

this distribution, remapped to the new names.

getAliases

public AliasSet[] getAliases()

Description copied from class: DataDistribution

Returns the fields that are referenced by this distribution. Note that it is valid for a distribution to reference no fields, in which case it should return an empty array. This method is used by the framework to validate the distribution is consistent with the type of the record.

Specified by:

getAliases in class DataDistribution

Returns:

the fields that are referenced by this distribution

getPartitioningFunction

protected PartitioningFunction getPartitioningFunction()

Description copied from class: PartialStaticDataDistribution

Subclasses must override this method to provide the partitioning function to be used

Specified by:

getPartitioningFunction in class PartialStaticDataDistribution

Returns:

a partition function

supportsLocalRepartition

protected boolean supportsLocalRepartition()

Description copied from class: PartialStaticDataDistribution

Subclasses may override to indicate that they support a local repartition

Overrides:

supportsLocalRepartition in class PartialStaticDataDistribution

Returns: