Class VennExpressionAdjunct

  • All Implemented Interfaces:
    FeedMaker

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

      • VennExpressionAdjunct

        public VennExpressionAdjunct()
    • Method Detail

      • 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
      • computeStreamability

        public PostureAndSweep computeStreamability​(ContextItemStaticInfoEE contextInfo,
                                                    java.util.List<java.lang.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

        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