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org.apache.crunch.lib
Class PTables

java.lang.Object
  org.apache.crunch.lib.PTables

public class PTables
extends Object

Methods for performing common operations on PTables.

Constructor Summary

PTables()

Method Summary

static <K,V> PTable<K,V>	asPTable(PCollection<Pair<K,V>> pcollect) Convert the given PCollection<Pair<K, V>> to a PTable<K, V>.
static <K,V> Pair<K,V>	getDetachedValue(PTableType<K,V> tableType, Pair<K,V> value) Create a detached value for a table Pair.
static <K,V> Pair<K,Iterable<V>>	getGroupedDetachedValue(PGroupedTableType<K,V> groupedTableType, Pair<K,Iterable<V>> value) Created a detached value for a PGroupedTable value.
static <K,V> PCollection<K>	keys(PTable<K,V> ptable) Extract the keys from the given PTable<K, V> as a PCollection<K>.
static <K1,K2,V> PTable<K2,V>	mapKeys(PTable<K1,V> ptable, MapFn<K1,K2> mapFn, PType<K2> ptype) Maps a PTable<K1, V> to a PTable<K2, V> using the given MapFn<K1, K2> on the keys of the PTable.
static <K1,K2,V> PTable<K2,V>	mapKeys(String name, PTable<K1,V> ptable, MapFn<K1,K2> mapFn, PType<K2> ptype) Maps a PTable<K1, V> to a PTable<K2, V> using the given MapFn<K1, K2> on the keys of the PTable.
static <K,U,V> PTable<K,V>	mapValues(PGroupedTable<K,U> ptable, MapFn<Iterable<U>,V> mapFn, PType<V> ptype) An analogue of the mapValues function for PGroupedTable<K, U> collections.
static <K,U,V> PTable<K,V>	mapValues(PTable<K,U> ptable, MapFn<U,V> mapFn, PType<V> ptype) Maps a PTable<K, U> to a PTable<K, V> using the given MapFn<U, V> on the values of the PTable.
static <K,U,V> PTable<K,V>	mapValues(String name, PGroupedTable<K,U> ptable, MapFn<Iterable<U>,V> mapFn, PType<V> ptype) An analogue of the mapValues function for PGroupedTable<K, U> collections.
static <K,U,V> PTable<K,V>	mapValues(String name, PTable<K,U> ptable, MapFn<U,V> mapFn, PType<V> ptype) Maps a PTable<K, U> to a PTable<K, V> using the given MapFn<U, V> on the values of the PTable.
static <K,V> PCollection<V>	values(PTable<K,V> ptable) Extract the values from the given PTable<K, V> as a PCollection<V>.

Methods inherited from class java.lang.Object

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

Constructor Detail

PTables

public PTables()

Method Detail

asPTable

public static <K,V> PTable<K,V> asPTable(PCollection<Pair<K,V>> pcollect)

Convert the given PCollection<Pair<K, V>> to a PTable<K, V>.

Parameters:

pcollect - The PCollection to convert

Returns:

A PTable that contains the same data as the input PCollection

mapKeys

public static <K1,K2,V> PTable<K2,V> mapKeys(PTable<K1,V> ptable,
                                             MapFn<K1,K2> mapFn,
                                             PType<K2> ptype)

Maps a PTable<K1, V> to a PTable<K2, V> using the given MapFn<K1, K2> on the keys of the PTable.

Parameters:

ptable - The PTable to be mapped

mapFn - The mapping function

ptype - The PType for the returned keys

Returns:

A new PTable<K2, V> instance

mapKeys

public static <K1,K2,V> PTable<K2,V> mapKeys(String name,
                                             PTable<K1,V> ptable,
                                             MapFn<K1,K2> mapFn,
                                             PType<K2> ptype)

Maps a PTable<K1, V> to a PTable<K2, V> using the given MapFn<K1, K2> on the keys of the PTable.

Parameters:

name - The name of the transform

ptable - The PTable to be mapped

mapFn - The mapping function

ptype - The PType for the returned keys

Returns:

A new PTable<K2, V> instance

mapValues

public static <K,U,V> PTable<K,V> mapValues(PTable<K,U> ptable,
                                            MapFn<U,V> mapFn,
                                            PType<V> ptype)

Maps a PTable<K, U> to a PTable<K, V> using the given MapFn<U, V> on the values of the PTable.

Parameters:

ptable - The PTable to be mapped

mapFn - The mapping function

ptype - The PType for the returned values

Returns:

A new PTable<K, V> instance

mapValues

public static <K,U,V> PTable<K,V> mapValues(String name,
                                            PTable<K,U> ptable,
                                            MapFn<U,V> mapFn,
                                            PType<V> ptype)

Maps a PTable<K, U> to a PTable<K, V> using the given MapFn<U, V> on the values of the PTable.

Parameters:

name - The name of the transform

ptable - The PTable to be mapped

mapFn - The mapping function

ptype - The PType for the returned values

Returns:

A new PTable<K, V> instance

mapValues

public static <K,U,V> PTable<K,V> mapValues(PGroupedTable<K,U> ptable,
                                            MapFn<Iterable<U>,V> mapFn,
                                            PType<V> ptype)

An analogue of the mapValues function for PGroupedTable<K, U> collections.

Parameters:

ptable - The PGroupedTable to be mapped

mapFn - The mapping function

ptype - The PType for the returned values

Returns:

A new PTable<K, V> instance

mapValues

public static <K,U,V> PTable<K,V> mapValues(String name,
                                            PGroupedTable<K,U> ptable,
                                            MapFn<Iterable<U>,V> mapFn,
                                            PType<V> ptype)

An analogue of the mapValues function for PGroupedTable<K, U> collections.

Parameters:

name - The name of the operation

ptable - The PGroupedTable to be mapped

mapFn - The mapping function

ptype - The PType for the returned values

Returns:

A new PTable<K, V> instance

keys

public static <K,V> PCollection<K> keys(PTable<K,V> ptable)

Extract the keys from the given PTable<K, V> as a PCollection<K>.

Parameters:

ptable - The PTable

Returns:

A PCollection<K>

values

public static <K,V> PCollection<V> values(PTable<K,V> ptable)

Extract the values from the given PTable<K, V> as a PCollection<V>.

Parameters:

ptable - The PTable

Returns:

A PCollection<V>

getDetachedValue

public static <K,V> Pair<K,V> getDetachedValue(PTableType<K,V> tableType,
                                               Pair<K,V> value)

Create a detached value for a table Pair.

Parameters:

tableType - The table type

value - The value from which a detached value is to be created

Returns:

The detached value

See Also:

PType.getDetachedValue(Object)

getGroupedDetachedValue

public static <K,V> Pair<K,Iterable<V>> getGroupedDetachedValue(PGroupedTableType<K,V> groupedTableType,
                                                                Pair<K,Iterable<V>> value)

Created a detached value for a PGroupedTable value.

Parameters:

groupedTableType - The grouped table type

value - The value from which a detached value is to be created

Returns:

The detached value

See Also:

PType.getDetachedValue(Object)