Package com.saxonica.ee.stream.adjunct

## Class CurrentMergeGroupStreamer

- java.lang.Object
- - com.saxonica.ee.stream.adjunct.StreamingAdjunct
  - - com.saxonica.ee.stream.adjunct.TransmissionAdjunct
    - - com.saxonica.ee.stream.adjunct.CurrentMergeGroupStreamer

- All Implemented Interfaces:
    `FeedMaker`

      public class CurrentMergeGroupStreamer
      extends TransmissionAdjunct

  Generate streaming code for a call on current-merge-group().

- - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `CurrentMergeGroupStreamer()` |

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `PostureAndSweep` | `computeStreamability​(ContextItemStaticInfoEE contextInfo, java.util.List<java.lang.String> reasons)` | Compute the posture and sweep of this expression as defined in the W3C streamability specifications.
    `ItemFeed` | `makeItemFeed​(WatchManager watchManager, ItemFeed out, XPathContext context)` |
    `Trigger` | `makeTransmissionFlow​(WatchManager watchManager, Expression exp, ItemFeed out, XPathContext context)` | Make a Trigger that implements this expression in streaming mode.
    `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)

    - ### Methods inherited from class com.saxonica.ee.stream.adjunct.TransmissionAdjunct

      `getWatchMaker`

    - ### Methods inherited from class com.saxonica.ee.stream.adjunct.StreamingAdjunct

      `findConsumingArg, getConfiguration, getDefaultFeedMaker, getExpression, getFeedMaker, makeStreamingAdjunct, setConfiguration, setExpression`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### CurrentMergeGroupStreamer

          public CurrentMergeGroupStreamer()

  - ### Method Detail

    - #### computeStreamability

          public PostureAndSweep computeStreamability​(ContextItemStaticInfoEE contextInfo,
                                                      java.util.List<java.lang.String> reasons)

      Description copied from class: `StreamingAdjunct`
      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. The implementation should have the side-effect of computing the streamability of all subexpressions, recursively.
      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; the contents are human-readable messages explaining why the expression is not streamable.
      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

    - #### makeTransmissionFlow

          public Trigger makeTransmissionFlow​(WatchManager watchManager,
                                              Expression exp,
                                              ItemFeed out,
                                              XPathContext context)
                                       throws XPathException

      Description copied from class: `TransmissionAdjunct`
      Make a Trigger that implements this expression in streaming mode. This method is used for an expression that is striding or crawling, and it delivers a Trigger connected to a sequence of Feeds which together have the effect of delivering a sequence of events and/or items that together represent the results of this instruction. This method MUST be implemented for every expression that has an operand whose usage is transmission (and for every such operand).
      Overrides:
        `makeTransmissionFlow` in class `TransmissionAdjunct`
      Parameters:
        `watchManager` - the WatchManager that fires this trigger
        `exp` - the expression
        `out` - the next action in the push pipeline for evaluation
        `context` - the XPath dynamic context
      Returns:
        the Trigger (a Watch with a pattern)
      Throws:
        `XPathException` - if a dynamic evaluation error occurs.

    - #### makeItemFeed

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

      Throws:
        `XPathException`