Contents
This sample demonstrates one use of the Aggregate operator. The time-based aggregate uses elapsed time to manage windows. This example uses two-second windows to compute the average price per share of symbols.
Consider the following problem: You are interested in the average price per share of a stock over some number of trades. You also want to know if the stock is active or not. If you get fewer than the requisite number of trades during some time period, then you conclude that the stock is relatively inactive. If you see more than that number of trades in the time period, the stock is very active.
This problem can be solved using an Aggregate with two window dimensions, one for the number of trades (as tuples), and another for time period. The time period is computed as a field-based aggregate using a timestamp field. In the following example, the first tuple emitted from Aggregate2Dimensions shows the average of five tuples. The second emitted tuple shows the average of only two tuples because only those two tuples fall within the time window as defined by the second dimension. The third tuple is emitted because five tuples had been received by Aggregate2Dimensions since the last five tuple group. However, because the first two of those input tuples had been calculated into the second emitted tuple, there are only three tuples available to be used to calculate the average. The numberShares, firstSeqnum, and lastSeqnum fields reflect this fact.
In StreamBase Studio, import this sample with the following steps:
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From the top-level menu, click >.
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Enter
sample groupto narrow the list of options. -
Select Operator sample group from the Data Constructs and Operators category.
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Click .
StreamBase Studio creates a single project for all the operator samples.
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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.
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Open the
src/main/eventflow/com.tibco.sb.sample.operatorfolder. -
Open the
AggregateByDim.sbappfile and click the
Run button. This opens the SB
Test/Debug perspective and starts the module.
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In the Output Streams view, select the AvgPricePSOut 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: the first tuple received will open a window that will close after receiving either five tuples or a tuple with time greater than or equal to
60. -
In the Manual Input view, enter
1,AMAT,20, and1in the seqnum, symbol, price, and time fields, respectively. -
Click , and observe that no output is displayed yet in the Output Streams view.
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Enter
2,AMAT,21, and11in the seqnum, symbol, price, and time fields, respectively. -
Click , and observe that no output is displayed yet in the Output Streams view.
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Enter
3,AMAT,22, and21in the seqnum, symbol, price, and time fields, respectively. -
Click , and observe that no output is displayed yet in the Output Streams view.
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Enter
4,AMAT,23, and31in the seqnum, symbol, price, and time fields, respectively. -
Click , and observe that no output is displayed yet in the Output Streams view.
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Enter
5,AMAT,24, and41in the seqnum, symbol, price, and time fields, respectively. -
Click , and observe this line in the Output Streams view:
symbol=AMAT, numberShares=5, averagePricePerShare=22.0,
lowerBoundTimeWindow=0.0, upperBoundTimeWindow=60.0, firstSeqnum=1, lastSeqnum=5This input causes the Aggregate operator to close the first window, which triggers the release of the output tuple.
Tip
If output data is too long to easily see in the Output Streams grid, click a row to display its field data in the Display Fields pane below the table.
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Enter
6,AMAT,25, and61in the seqnum, symbol, price, and time fields, respectively.This input causes a new window to open. Like the first window, it will close after receiving either five tuples or a tuple with time greater than or equal to 60.
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Click , and observe that no output is displayed yet in the Output Streams view.
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Enter
7,AMAT,26, and119in the seqnum, symbol, price, and time fields, respectively. -
Click , and observe that no output is displayed yet in the Output Streams view.
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Enter
8,AMAT,27, and121in the seqnum, symbol, price, and time fields, respectively. -
Click , and observe this line in the Output Streams view:
symbol=AMAT, numberShares=3, averagePricePerShare=25.5,
lowerBoundTimeWindow=60.0, upperBoundTimeWindow=120.0, firstSeqnum=6, lastSeqnum=7 -
Enter
9,AMAT,26, and150in the seqnum, symbol, price, and time fields, respectively. -
Click , and observe that no output is displayed yet in the Output Streams view.
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Enter
10,AMAT,26, and151in the seqnum, symbol, price, and time fields, respectively. -
Click , and observe this line in the Output Streams view:
symbol=AMAT, numberShares=3, averagePricePerShare=28,
lowerBoundTimeWindow=120.0, upperBoundTimeWindow=180.0, firstSeqnum=8, lastSeqnum=10 -
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.