io.github.privacystreams.core.transformations.group

Class Groupers

java.lang.Object

io.github.privacystreams.core.transformations.group.Groupers

@PSOperatorWrapper
public class Groupers
extends java.lang.Object

A helper class to access grouping functions

Constructor Summary

Constructors

Constructor and Description
Groupers()

Method Summary

Modifier and Type	Method and Description
static PStreamTransformation	groupBy(java.lang.String groupField) Group the items according to a field.
static PStreamTransformation	localGroupBy(java.lang.String groupField) Group the **contiguous** items according to a field.
static PStreamTransformation	unGroup(java.lang.String unGroupField, java.lang.String newField) Un-group a list field in each item to multiple items.

Methods inherited from class java.lang.Object

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

Constructor Detail

Groupers

public Groupers()

Method Detail

groupBy

public static PStreamTransformation groupBy(java.lang.String groupField)

Group the items according to a field. After grouping, the items in the new stream will only have two fields. One is the field used for grouping by. Another is "grouped_items" which is a list of grouped Items. Eg. `groupBy("x")` will group the items with same "x" field, and the item in the stream after groupping will contain two fields: "x" and "grouped_items".

Parameters:

groupField - the field used to group the items in current stream.

Returns:

the grouper function.

localGroupBy

public static PStreamTransformation localGroupBy(java.lang.String groupField)

Group the **contiguous** items according to a field. After grouping, the items in the new stream will only have two fields. One is the field used for grouping by. Another is "grouped_items" which is a list of grouped Items. Eg. `localGroupBy("x")` will group the contiguous items with same "x" field, and the item in the stream after groupping will contain two fields: "x" and "grouped_items".

Parameters:

groupField - the field used to group the items in current stream.

Returns:

the grouper function.

unGroup

public static PStreamTransformation unGroup(java.lang.String unGroupField,
                                            java.lang.String newField)

Un-group a list field in each item to multiple items. Each element in the list will be a new field in each item of the new stream. After un-grouping, the items in the new streams will have the same amount of fields as the original stream. However, the list field (`unGroupField`) will be replaced by a new field (`newField`). Eg. `unGroup("emails", "email")` will un-group the "emails" field (which is a list) in an item to several new items with a "email" field.

Parameters:

unGroupField - the field to un-group, whose value should be a list

newField - the new field name in the new stream

Returns:

The un-group function