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java.lang.Object com.saxonica.expr.ee.MultithreadedContextMappingIterator
public final class MultithreadedContextMappingIterator
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 |
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Fields inherited from interface net.sf.saxon.om.SequenceIterator |
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GROUNDED, LAST_POSITION_FINDER, LOOKAHEAD |
Constructor Summary | |
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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 | |
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void |
close()
Close the iterator. |
Item |
current()
Get the current value in the sequence (the one returned by the most recent call on next()). |
SequenceIterator |
getAnother()
Get another SequenceIterator that iterates over the same items as the original, but which is repositioned at the start of the sequence. |
int |
getProperties()
Get properties of this iterator, as a bit-significant integer. |
Item |
next()
Get the next item in the sequence. |
int |
position()
Get the current position. |
Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
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public MultithreadedContextMappingIterator(Expression action, XPathContextMinor context, int threads) throws XPathException
action
- the mapping expression to be appliedcontext
- 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.
XPathException
Method Detail |
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public Item next() throws XPathException
SequenceIterator
next
in interface SequenceIterator
XPathException
- if an error occurs retrieving the next itempublic Item current()
SequenceIterator
current
in interface SequenceIterator
public int position()
SequenceIterator
This method does not change the state of the iterator.
position
in interface SequenceIterator
public void close()
SequenceIterator
(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.)
close
in interface SequenceIterator
public SequenceIterator getAnother() throws XPathException
SequenceIterator
This method allows access to all the items in the sequence without disturbing the current position of the iterator. Internally, its main use is in evaluating the last() function.
This method does not change the state of the iterator.
getAnother
in interface SequenceIterator
XPathException
- if any error occurspublic int getProperties()
getProperties
in interface SequenceIterator
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.
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