Contents
This topic describes AggregateByPredicate.sbapp, the
Aggregate operator predicate dimension sample.
This sample demonstrates use of the predicate-based Aggregate operator. The
predicate-based aggregate uses Boolean strings sent to a control port to open, emit
from, and close aggregate windows. Data entered on the TradesIn port are not processed until true is sent to the
EmitWindow or CloseWindow
field of the control port, or both.
The following table lists the predicate expressions entered in the three predicate dimension fields of the Edit Dimension dialog for this sample.
| Predicate Field | Expression Entered |
|---|---|
| Open a window in the current group when | input1.OpenWindow |
| For windows in the current group, Emit if | input1.EmitWindow || input1.CloseWindow |
| For windows in the current group, Close if | input1.CloseWindow |
The input1 in these expressions refers to input port 1
of the Aggregate operator. In this sample's case, a Union operator precedes the input
port of the Aggregate operator, which combines two input streams, WindowControl and TradesIn. You send
tuples to the WindowControl stream to open, emit, or
close windows. OpenWindow, EmitWindow, and CloseWindow are all
fields of type bool in the schema of the WindowControl
stream. So you need only send true or false to one or more of these ports to cause a window control
action.
Thus, opening an aggregate window is a matter of sending a tuple containing
true in the OpenWindow
field of the WindowControl port. With a window open, you
can now send tuples to the TradesIn stream. However, a
computation based on the input trade values is not emitted from the window until you
send a tuple containing true to the EmitWindow field of
the WindowControl port.
In StreamBase Studio, import this sample with the following steps:
-
From the top-level menu, click >.
-
Enter
sample groupto narrow the list of options. -
Select Operator sample group from the Data Constructs and Operators category.
-
Click .
StreamBase Studio creates a single project for the all operator samples.
-
In the Project Explorer view, open the sample you just loaded.
If you see red marks on a project folder, wait a moment for the project to load its features.
If the red marks do not resolve themselves after a minute, select the project, right-click, and select > from the context menu.
-
Open the
src/main/eventflow/com.tibco.sb.sample.operatorfolder. -
Open the
AggregateByPredicate.sbappfile and click the
Run button. This opens the SB
Test/Debug perspective and starts the module.
-
No output is displayed in the Output Streams view yet, but the dequeuer is prepared to receive output. This view will eventually show the output of the application.
-
In the Manual Input view, select the
WindowControlstream from the Input stream drop-down list. -
In the
OpenWindowfield, typetrue, then click . -
Select
TradesInin the Input stream drop-down list. -
Enter several volume and price pairs, clicking after each pair. For example, enter Volume=1000, Price=39.45. Make up any pairs of numbers and send them to the application. Notice that no output is showing in the Output Streams view, but you can see the tuples you are sending by switching to the Input Streams view.
-
In the Input stream drop-down, re-select
WindowControl. -
Click , then enter
truein theEmitWindowfield and click . Notice that a single tuple now appears in the Output Streams view, showing the calculated VWAP for the volume and price tuples you sent. (Select the tuple to see it in more detail in the Details pane.) -
Re-select
TradesInin the Input stream drop-down list, and send several more pairs of volume and price data. -
Re-select
WindowControlin the Input stream drop-down list. Again click , then entertruein both theEmitWindowandCloseWindowfields. Click Send Data. Another tuple displays in the Output Streams view. -
When done, press F9 or click the
Terminate EventFlow Fragment button.
When you load the sample into StreamBase Studio, Studio copies the sample project's files to your Studio workspace, which is normally part of your home directory, with full access rights.
Important
Load this sample in StreamBase Studio, and thereafter use the Studio workspace copy of the sample to run and test it, even when running from the command prompt.
Using the workspace copy of the sample avoids permission problems. The default workspace location for this sample is:
studio-workspace/sample_operator
See Default Installation
Directories for the default location of studio-workspace on your system.