Class VennExpressionAdjunct

All Implemented Interfaces:
FeedMaker

public class VennExpressionAdjunct extends TransmissionAdjunct
Class to handle streaming of union, intersect, and except expressions
  • Constructor Details Link icon

    • VennExpressionAdjunct Link icon

      public VennExpressionAdjunct()
  • Method Details Link icon

    • toStreamingPattern Link icon

      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
    • computeStreamability Link icon

      public PostureAndSweep computeStreamability(ContextItemStaticInfoEE contextInfo, List<String> reasons)
      Get the "sweep" of this expression as defined in the W3C streamability specifications. This provides an assessment of stylesheet code against the W3C criteria for guaranteed streamability, and is implemented to allow these criteria to be tested. It is not the case that all expression that emerge as streamable from this analysis are currently capable of being streamed by Saxon
      Overrides:
      computeStreamability in class StreamingAdjunct
      Parameters:
      contextInfo - static information about the context item
      reasons - the caller may supply a list, in which case the implementation may add to this
      Returns:
      the posture and sweep of the expression
    • getWatchMaker Link icon

      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 Link icon

      public ItemFeed makeItemFeed(WatchManager watchManager, ItemFeed out, XPathContext context) throws XPathException
      Throws:
      XPathException