Class DocumentSorterAdjunct

All Implemented Interfaces:
FeedMaker

public class DocumentSorterAdjunct extends TransmissionAdjunct implements FeedMaker
Generate streaming code for a document sorting expression node. This will only be used to support streaming of a path expression of the form child::* / ancestor::*, where the only operation needed is filtering to remove duplicate ancestors (and returning of ancestors in document order). In addition, if the expression a mixture of striding and grounded nodes, then we can sort it because the streamed nodes retain their order (bug 29507)
  • Constructor Details

    • DocumentSorterAdjunct

      public DocumentSorterAdjunct()
  • Method Details

    • computeStreamability

      public PostureAndSweep computeStreamability(ContextItemStaticInfoEE contextInfo, List<String> reasons)
      Compute the posture and sweep of this expression as defined in the W3C streamability specifications. This must be implemented in all subclasses that don't use the general streamability rules.
      Overrides:
      computeStreamability in class StreamingAdjunct
      Parameters:
      contextInfo - Information about the context item type and posture
      reasons - the caller may supply a list, in which case the implementation may add to this
      Returns:
      the posture and sweep of the expression
    • toStreamingPattern

      public Pattern toStreamingPattern(Configuration config)
      Convert this expression to a streaming pattern (a pattern used internally to match nodes during push processing of an event stream)
      Overrides:
      toStreamingPattern in class StreamingAdjunct
      Parameters:
      config - the Saxon configuration
      Returns:
      the equivalent pattern if conversion succeeds; otherwise null
    • getWatchMaker

      public WatchMaker getWatchMaker(boolean forGrouping) throws XPathException
      Description copied from class: StreamingAdjunct
      Get a WatchMaker, a factory class that creates a Watch to evaluate this expression in streaming mode. This method will only be called if the getImplementationMethod() method of the expression includes the value Expression.WATCH_METHOD
      Overrides:
      getWatchMaker in class TransmissionAdjunct
      Parameters:
      forGrouping - true if the selected items are being grouped
      Returns:
      a Watchmaker to evaluate the expression, or null if it is not streamable with respect to the specificed argument.
      Throws:
      XPathException - in the event of a failure
    • makeItemFeed

      public ItemFeed makeItemFeed(WatchManager watchManager, ItemFeed out, XPathContext context) throws XPathException
      Specified by:
      makeItemFeed in interface FeedMaker
      Throws:
      XPathException
    • getFeedMaker

      public FeedMaker getFeedMaker(int arg) throws XPathException
      Description copied from class: StreamingAdjunct
      Get a FeedMaker, a factory class that creates a Feed to evaluate this expression in streaming mode. In many cases the StreamingAdjunct is itself a FeedMaker, in which case it returns itself. But where an expression has several operands, it will typically create different feeds depending on which argument is the streamed input, and in such cases the individual StreamingAdjunct makes the decision which feed to use, by returning an appropriate FeedMaker.
      Overrides:
      getFeedMaker in class StreamingAdjunct
      Parameters:
      arg - identifies the argument with respect to which the expression is to be inverted: usually 0 to indicate the first argument is the value that is streamed. Argument numbering is the same as the sequence of arguments/operands returned by the method Expression.operands()
      Returns:
      a FeedMaker to evaluate the expression, or null if it is not streamable with respect to the specificed argument.
      Throws:
      XPathException - in the event of a failure