com.saxonica.ee.optim

Class MultithreadedContextMappingIterator

java.lang.Object

com.saxonica.ee.optim.MultithreadedContextMappingIterator

All Implemented Interfaces:

SequenceIterator

public final class MultithreadedContextMappingIterator
extends java.lang.Object
implements SequenceIterator

This class performs the same role as ContextMappingIterator, but using multiple threads.

It merges a sequence of sequences into a single flat sequence. It takes as inputs an iteration, and an "action" expression to be applied to each Item returned by that iteration, with that item as the context item. The action expression itself returns another iterator. The result is an iteration of the concatenation of all the iterations returned by the action expression.

Field Summary

Fields inherited from interface net.sf.saxon.om.SequenceIterator

ATOMIZING, GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD

Constructor Summary

Constructors

Constructor and Description
MultithreadedContextMappingIterator(Expression action, XPathContextMinor context, int threads) Construct an Iterator that will apply a specified action expression to each Item returned by the current iterator of the supplied dynamic context.

Method Summary

Modifier and Type	Method and Description
void	close() Close the iterator.
int	getProperties() Get properties of this iterator, as a bit-significant integer.
Item	next() Get the next item in the sequence.

Methods inherited from class java.lang.Object

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

Constructor Detail

MultithreadedContextMappingIterator

public MultithreadedContextMappingIterator(Expression action,
                                           XPathContextMinor context,
                                           int threads)
                                    throws XPathException

Construct an Iterator that will apply a specified action expression to each Item returned by the current iterator of the supplied dynamic context.

Parameters:

action - the mapping expression to be applied

context - the processing context. The action expression is applied to each item returned by context.getCurrentIterator() in turn.

threads - the number of threads to be used (in addition to the base evaluation thread) These threads are used to evaluate the action expression. The current thread is used to evaluate the base iterator and to gather the results of invoking the action expressions in the right order.

Throws:

XPathException

Method Detail

next

public Item next()
          throws XPathException

Description copied from interface: SequenceIterator

Get the next item in the sequence. This method changes the state of the iterator.

Specified by:

next in interface SequenceIterator

Returns:

the next item, or null if there are no more items. Once a call on next() has returned null, no further calls should be made. The preferred action for an iterator if subsequent calls on next() are made is to return null again, and all implementations within Saxon follow this rule.

Throws:

XPathException - if an error occurs retrieving the next item

close

public void close()

Description copied from interface: SequenceIterator

Close the iterator. This indicates to the supplier of the data that the client does not require any more items to be delivered by the iterator. This may enable the supplier to release resources. After calling close(), no further calls on the iterator should be made; if further calls are made, the effect of such calls is undefined.

(Currently, closing an iterator is important only when the data is being "pushed" in another thread. Closing the iterator terminates that thread and means that it needs to do no additional work. Indeed, failing to close the iterator may cause the push thread to hang waiting for the buffer to be emptied.)

Specified by:

close in interface SequenceIterator

getProperties

public int getProperties()

Get properties of this iterator, as a bit-significant integer.

Specified by:

getProperties in interface SequenceIterator

Returns:

the properties of this iterator. This will be some combination of properties such as SequenceIterator.GROUNDED, SequenceIterator.LAST_POSITION_FINDER, and SequenceIterator.LOOKAHEAD. It is always acceptable to return the value zero, indicating that there are no known special properties. It is acceptable for the properties of the iterator to change depending on its state.