com.espertech.esper.view.window
Class TimeBatchView

java.lang.Object
  extended by com.espertech.esper.view.ViewSupport
      extended by com.espertech.esper.view.window.TimeBatchView
All Implemented Interfaces:
BatchingDataWindowView, CloneableView, DataWindowView, EventCollection, View, Viewable, Iterable<EventBean>

public final class TimeBatchView
extends ViewSupport
implements CloneableView, BatchingDataWindowView

A data view that aggregates events in a stream and releases them in one batch at every specified time interval. The view works similar to a time_window but in not continuous. The view releases the batched events after the interval as new data to child views. The prior batch if not empty is released as old data to child view. The view doesn't release intervals with no old or new data. It also does not collect old data published by a parent view. For example, we want to calculate the average of IBM stock every hour, for the last hour. The view accepts 2 parameter combinations. (1) A time interval is supplied with a reference point - based on this point the intervals are set. (1) A time interval is supplied but no reference point - the reference point is set when the first event arrives. If there are no events in the current and prior batch, the view will not invoke the update method of child views. In that case also, no next callback is scheduled with the scheduling service until the next event arrives.


Field Summary
 
Fields inherited from class com.espertech.esper.view.ViewSupport
parent
 
Constructor Summary
TimeBatchView(TimeBatchViewFactory timeBatchViewFactory, StatementContext statementContext, long msecIntervalSize, Long referencePoint, ViewUpdatedCollection viewUpdatedCollection)
          Constructor.
 
Method Summary
 View cloneView(StatementContext statementContext)
          Duplicates the view.
protected static long computeWaitMSec(long current, long reference, long interval)
          Given a current time and a reference time and an interval size, compute the amount of milliseconds till the next interval.
 EventType getEventType()
          Provides metadata information about the type of object the event collection contains.
 Long getInitialReferencePoint()
          Gets the reference point to use to anchor interval start and end dates to.
 long getMsecIntervalSize()
          Returns the interval size in milliseconds.
 boolean isEmpty()
          Returns true if the window is empty, or false if not empty.
 Iterator<EventBean> iterator()
          Allows iteration through all elements in this event collection.
protected  void sendBatch()
          This method updates child views and clears the batch of events.
 String toString()
           
 void update(EventBean[] newData, EventBean[] oldData)
          Notify that data has been added or removed from the Viewable parent.
 
Methods inherited from class com.espertech.esper.view.ViewSupport
addView, dumpChildViews, dumpUpdateParams, dumpUpdateParams, findDescendent, getParent, getViews, hasViews, removeView, setParent, updateChildren, updateChildren
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 
Methods inherited from interface com.espertech.esper.view.View
getParent, setParent
 
Methods inherited from interface com.espertech.esper.view.Viewable
addView, getViews, hasViews, removeView
 

Constructor Detail

TimeBatchView

public TimeBatchView(TimeBatchViewFactory timeBatchViewFactory,
                     StatementContext statementContext,
                     long msecIntervalSize,
                     Long referencePoint,
                     ViewUpdatedCollection viewUpdatedCollection)
Constructor.

Parameters:
msecIntervalSize - is the number of milliseconds to batch events for
referencePoint - is the reference point onto which to base intervals, or null if there is no such reference point supplied
viewUpdatedCollection - is a collection that the view must update when receiving events
timeBatchViewFactory - fr copying this view in a group-by
statementContext - is required view services
Method Detail

cloneView

public View cloneView(StatementContext statementContext)
Description copied from interface: CloneableView
Duplicates the view.

Expected to return a same view in initialized state for grouping.

Specified by:
cloneView in interface CloneableView
Parameters:
statementContext - is services for the view
Returns:
duplicated view

getMsecIntervalSize

public final long getMsecIntervalSize()
Returns the interval size in milliseconds.

Returns:
batch size

getInitialReferencePoint

public final Long getInitialReferencePoint()
Gets the reference point to use to anchor interval start and end dates to.

Returns:
is the millisecond reference point.

getEventType

public final EventType getEventType()
Description copied from interface: EventCollection
Provides metadata information about the type of object the event collection contains.

Specified by:
getEventType in interface EventCollection
Returns:
metadata for the objects in the collection

update

public final void update(EventBean[] newData,
                         EventBean[] oldData)
Description copied from interface: View
Notify that data has been added or removed from the Viewable parent. The last object in the newData array of objects would be the newest object added to the parent view. The first object of the oldData array of objects would be the oldest object removed from the parent view. If the call to update contains new (inserted) data, then the first argument will be a non-empty list and the second will be empty. Similarly, if the call is a notification of deleted data, then the first argument will be empty and the second will be non-empty. Either the newData or oldData will be non-null. This method won't be called with both arguments being null, but either one could be null. The same is true for zero-length arrays. Either newData or oldData will be non-empty. If both are non-empty, then the update is a modification notification. When update() is called on a view by the parent object, the data in newData will be in the collection of the parent, and its data structures will be arranged to reflect that. The data in oldData will not be in the parent's data structures, and any access to the parent will indicate that that data is no longer there.

Specified by:
update in interface View
Parameters:
newData - is the new data that has been added to the parent view
oldData - is the old data that has been removed from the parent view

sendBatch

protected final void sendBatch()
This method updates child views and clears the batch of events. We schedule a new callback at this time if there were events in the batch.


isEmpty

public boolean isEmpty()
Returns true if the window is empty, or false if not empty.

Returns:
true if empty

iterator

public final Iterator<EventBean> iterator()
Description copied from interface: EventCollection
Allows iteration through all elements in this event collection. The iterator will return the elements in the collection in their natural order, or, if there is no natural ordering, in some unpredictable order.

Specified by:
iterator in interface EventCollection
Specified by:
iterator in interface Iterable<EventBean>
Returns:
an iterator which will go through all current elements in the collection.

toString

public final String toString()
Overrides:
toString in class Object

computeWaitMSec

protected static long computeWaitMSec(long current,
                                      long reference,
                                      long interval)
Given a current time and a reference time and an interval size, compute the amount of milliseconds till the next interval.

Parameters:
current - is the current time
reference - is the reference point
interval - is the interval size
Returns:
milliseconds after current time that marks the end of the current interval

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