Package net.sf.saxon.expr.sort
Class MergeGroupingIterator
java.lang.Object
net.sf.saxon.expr.sort.MergeGroupingIterator
- All Implemented Interfaces:
Closeable,AutoCloseable,LastPositionFinder,GroupIterator,SequenceIterator,LookaheadIterator
public class MergeGroupingIterator
extends Object
implements GroupIterator, LookaheadIterator, LastPositionFinder
An iterator that groups the result of merging several xsl:merge input streams, identifying
groups of adjacent items having the same merge key value
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Nested Class Summary
Nested classes/interfaces inherited from interface net.sf.saxon.om.SequenceIterator
SequenceIterator.Property -
Field Summary
Fields -
Constructor Summary
ConstructorsConstructorDescriptionMergeGroupingIterator(SequenceIterator p1, ItemOrderComparer comp, LastPositionFinder lpf) -
Method Summary
Modifier and TypeMethodDescriptionvoidclose()Close the iterator.Get the grouping key of the current groupintGet the last position (that is, the number of items in the sequence).Get properties of this iterator.booleanhasNext()Determine whether there are more items to come.Get an iterator over the members of the current group, in population order.iterateCurrentGroup(String source) 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, waitMethods inherited from interface net.sf.saxon.om.SequenceIterator
forEachOrFail, materialize
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Field Details
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compositeMergeKey
List<AtomicValue> compositeMergeKey
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Constructor Details
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MergeGroupingIterator
public MergeGroupingIterator(SequenceIterator p1, ItemOrderComparer comp, LastPositionFinder lpf) throws XPathException - Throws:
XPathException
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Method Details
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hasNext
public boolean hasNext()Description copied from interface:LookaheadIteratorDetermine whether there are more items to come. Note that this operation is stateless and it is not necessary (or usual) to call it before calling next(). It is used only when there is an explicit need to tell if we are at the last element.This method must not be called unless the result of getProperties() on the iterator includes the property
SequenceIterator.Property.LOOKAHEAD- Specified by:
hasNextin interfaceLookaheadIterator- Returns:
- true if there are more items in the sequence
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next
Description copied from interface:SequenceIteratorGet the next item in the sequence. This method changes the state of the iterator.- Specified by:
nextin interfaceSequenceIterator- 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
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close
public void close()Description copied from interface:SequenceIteratorClose 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.For example, the iterator returned by the unparsed-text-lines() function has a close() method that causes the underlying input stream to be closed, whether or not the file has been read to completion.
Closing an iterator is important 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:
closein interfaceAutoCloseable- Specified by:
closein interfaceCloseable- Specified by:
closein interfaceSequenceIterator
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getLength
Description copied from interface:LastPositionFinderGet the last position (that is, the number of items in the sequence). This method is non-destructive: it does not change the state of the iterator. The result is undefined if the next() method of the iterator has already returned null. This method must not be called unless the result of getProperties() on the iterator includes the bit settingSequenceIterator.Property.LAST_POSITION_FINDER- Specified by:
getLengthin interfaceLastPositionFinder- Returns:
- the number of items in the sequence
- Throws:
XPathException- if an error occurs evaluating the sequence in order to determine the number of items
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getProperties
Description copied from interface:SequenceIteratorGet properties of this iterator.- Specified by:
getPropertiesin interfaceSequenceIterator- Returns:
- the properties of this iterator. This will be some combination of
properties such as
SequenceIterator.Property.GROUNDED,SequenceIterator.Property.LAST_POSITION_FINDER, andSequenceIterator.Property.LOOKAHEAD. It is always acceptable to return the default valueEnumSet.noneOf(Property.class), indicating that there are no known special properties. It is acceptable (though unusual) for the properties of the iterator to change depending on its state.
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getCurrentGroupingKey
Description copied from interface:GroupIteratorGet the grouping key of the current group- Specified by:
getCurrentGroupingKeyin interfaceGroupIterator- Returns:
- the current grouping key in the case of group-by or group-adjacent, or null in the case of group-starting-with and group-ending-with
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iterateCurrentGroup
Description copied from interface:GroupIteratorGet an iterator over the members of the current group, in population order. This must always be a clean iterator, that is, an iterator that starts at the first item of the group.- Specified by:
iterateCurrentGroupin interfaceGroupIterator- Returns:
- an iterator over all the members of the current group, in population order.
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iterateCurrentGroup
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