com.saxonica.stream.watch

Class GroupAdjacentWatch

java.lang.Object

com.saxonica.validate.AbstractWatch

com.saxonica.stream.watch.EventPushingWatch

com.saxonica.stream.watch.GroupingWatch

com.saxonica.stream.watch.GroupAdjacentWatch

All Implemented Interfaces:

Watch

public class GroupAdjacentWatch
extends GroupingWatch

This class implements GroupingFeed when the group-adjacent option is used. It contains the logic to decide whether an item starts a new group, based on computing the grouping key and comparing it with that of the previous item

Constructor Summary

Constructors

Constructor and Description
GroupAdjacentWatch(GroupVariableReference expression, Feed out, Stack<XPathContext> contextStack)

Method Summary

Methods

Modifier and Type	Method and Description
protected boolean	isStartOfNewGroup(boolean atStart, XPathContext context) Determine whether the current item is the start of a new group
void	open() Called at the start of the for-each-group instruction

Methods inherited from class com.saxonica.stream.watch.GroupingWatch

close, endSelectedParentNode, getControllingExpression, getLocalContext, setControllingExpression, setOuterFeed, setWatchManager, startSelectedParentNode

Methods inherited from class com.saxonica.stream.watch.EventPushingWatch

getContext, getContextStack, getExpression, getParentExpressionFeed, getResult, setParentExpressionFeed

Methods inherited from class com.saxonica.validate.AbstractWatch

getAnchorNode, getNamespaceResolver, getPipelineConfiguration, getSelection, notifySelectedLeafNode, setAnchorNode, setNamespaceResolver, setPipelineConfiguration, setSelection

Methods inherited from class java.lang.Object

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

Constructor Detail

GroupAdjacentWatch

public GroupAdjacentWatch(GroupVariableReference expression,
                  Feed out,
                  Stack<XPathContext> contextStack)

Method Detail

open

public void open()
          throws XPathException

Called at the start of the for-each-group instruction

Specified by:

open in interface Watch

Overrides:

open in class GroupingWatch

Throws:

XPathException

isStartOfNewGroup

protected boolean isStartOfNewGroup(boolean atStart,
                        XPathContext context)
                             throws XPathException

Determine whether the current item is the start of a new group

Specified by:

isStartOfNewGroup in class GroupingWatch

Parameters:

atStart - true if this item is the first in the population

context - the evaluation context. The item in question will be the context item

Returns:

true if this item is to be the first in a new group

Throws:

XPathException - if a dynamic error occurs