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# Gather Operator Sample

## About This Guide

The `Gather.sbapp` sample application has two EventFlow modules. The SimpleGather example uses a Gather operator to generate an alarm (a `true` value) for trades of 10,000 shares or more for a stock whose price is $200 or greater. The input stream contains the fields `Symbol`,`Volume`, and `Price`.

### Note

This is a very simple example which might be better done using a single Map operator, but it is instructive. For an example that truly requires a Gather operator, see the Compliance sample application.

The TimeoutGather example demonstrates the effect of the Optional Timeouts settings. In this case, when no input is received for ten seconds, Gather is forced to emit whatever tuple values it has accumulated, setting any fields not received to null. The input stream has two string fields: Type (which must be enqueued as either `Buy` or `Sell`) and Symbol (which can be any string).

## Importing This Sample into StreamBase Studio

In StreamBase Studio, import this sample with the following steps:

- From the top-level menu, click File → Load StreamBase Sample.

- Enter `operator` to narrow the list of options.

- Select Operator sample group from the Data Constructs and Operators category.

- Click OK.

StreamBase Studio creates a single project for all the operator samples.

## Running This Sample in StreamBase Studio

1. 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 Maven → Update Project from the context menu.

2. Open the `src/main/eventflow/com.tibco.sb.sample.operator` folder.

3. Open the `Gather.sbapp` file and click the Run button. This opens the SB Test/Debug perspective and starts the module.

4. In the Output Streams view, select the BigTradeAlarm output stream. No output is displayed at this point, but the dequeuer is prepared to receive output. This view will eventually show the output of the application.

5. In the Manual Input view, select the TradesIn input stream.

6. Enter `intc`, `10000`, and `201` in the Symbol, Volume, and Price fields, respectively

7. Click Send Data, and observe this data appears in the BigTradeAlarm stream:

       BigTradeAlarm=true

8. Enter `intc`, `10000`, and `199` in the Symbol, Volume, and Price fields, respectively

9. Click Send Data, and observe this data appears in the BigTradeAlarm stream:

       BigTradeAlarm=false

10. Enter `intc`, `1000`, and `201` in the Symbol, Volume, and Price fields, respectively

11. Click Send Data, and observe this data appears in the BigTradeAlarm stream:

        BigTradeAlarm=false

12. Enter `intc`, `1000`, and `187` in the Symbol, Volume, and Price fields, respectively

13. Click Send Data, and observe this data appears in the BigTradeAlarm stream:

        BigTradeAlarm=false

To run the TimeoutGather example:

1. 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 Maven → Update Project from the context menu.

2. Open the `src/main/eventflow/`packageName`` folder.

3. Open the `Gather.sbapp` file and click the Run button. This opens the SB Test/Debug perspective and starts the module.

4. In the Output Streams view, select the Matches output stream. No output is displayed at this point, but the dequeuer is prepared to receive output. This view will eventually show the output of the application.

5. In the Manual Input view, select the SimpleBuySellMatch input stream.

6. Enter `Buy` and `intc` in the Type and Symbol fields, respectively, and press Send Data.

7. Quickly change Type from `Buy` to `Sell` and press Send Data again.

8. Observe this data appear in the Matches stream:

       MatchedSymbol=intc

9. Now change Type from `Sell` back to `Buy` again, and press Send Data.

10. Do not send a Sell message. After 10 seconds, observe that the Gather operator times out, and writes the following to the Matches output stream:

        MatchedSymbol=<No Match: intc,null>

When done, press F9 or click the Terminate EventFlow Fragment button.

## Sample Location

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.