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Generate Alerts Using a Derived Window in SAP HANA Streaming Analytics

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Generate Alerts Using a Derived Window in SAP HANA Streaming Analytics
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Generate Alerts Using a Derived Window in SAP HANA Streaming Analytics

12/14/2018

Create and use a derived window to analyze events, filter data, and generate alerts.

You will learn

  • How to use a derived window to apply a filter to watch for events that should generate an alert


In this tutorial, you will add and configure a derived stream that will watch for events that need to generate an alert - by applying a filter.

However, rather than just using the standard Filter element, you will use the Derived Window element from the Palette since it gives you more flexibility. With this, you can apply the filter and also change the structure of the output event.

At this point in the tutorial series, if you don’t want to go through the process of creating this window using the visual editor, then you can simply switch to the CCL editor ( F6 ) and paste the CCL below into your project. From there, you can then skip to the last step to compile and test your project.


CREATE OUTPUT WINDOW ALARM_TEMP PRIMARY KEY DEDUCED KEEP ALL AS SELECT AVG_TEMP.MACHINEID MACHINEID , AVG_TEMP.EVENT_TIME EVENT_TIME , AVG_TEMP.AVG_TEMP AVG_TEMP , AVG_TEMP.MAX_TEMP MAX_TEMP , AVG_TEMP.LOCATION LOCATION , 'TEMPERATURE' ALARM_TYPE , 'Machine not maintaining' ALARM_DESC FROM AVG_TEMP WHERE AVG_TEMP.AVG_TEMP > AVG_TEMP.MAX_TEMP ;
Step 1: Add a derived window to generate alerts

Click on Derived Window in the Palette and drop it onto the canvas.

1-dropderivedwindow
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Step 2: Connect the new window to the event stream

Add a connector from AVG_TEMP to the new window.

add connector
With this new window added to your freezer_monitor project, based on the work you’ve done so far in this tutorial and the previous tutorial group (Get started with SAP HANA streaming analytics for SAP HANA, express edition), how many elements (not including connector arrows) are now on your canvas?
×
Step 3: Change the window name

Change the new window name to ALARM_TEMP, then press Enter.

rename to alarm temp
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Step 4: Add columns to the window

Click the Add Column Expression ( f(x) ) option shown below.

add column expression

Choose Copy Columns from Input from the menu to open the column selection dialog.

copy columns from input

Select all except for MIN_TEMP and TEMP_UNIT, then click OK.

select columns

Select the Add Column Expression ( f(x) ) option, then Column Expression to add a column to this window.

column expression

Repeat this step to add a second column.

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Step 5: Edit the column names and expressions

Rename the first new column to ALARM_TYPE, then press Enter.

rename expression

Rename the second new column to ALARM_DESC.

name expression

Double-click on simpleResultExpression6 to edit the expression.

edit expression

Enter 'TEMPERATURE' in the expression edit box for the ALARM_TYPE column. This will set the “type” of all alarms emitted by this window to the string “TEMPERATURE”. Press Enter to confirm your entry.

rename expression

Note that it’s important to enclose string values in single quotes in expressions.

Enter 'Machine not maintaining temperature' in the expression edit box for the ALARM_DESC column. Press Enter to confirm your entry.

rename second expression
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Step 6: Add a filter expression

Now click the Add Query Clause button.

add query

Choose Filter from the menu or press f.

add filter

You want to add a filter so that this window only contains rows for machines that have a current average temperature above the max specified for the machine.

Double-click on 1 under Other to edit the filter expression.

change filter expression

Change the filter expression to: AVG_TEMP.AVG_TEMP > AVG_TEMP.MAX_TEMP. Use Ctrl+Space for completion assist.

filter expression
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Step 7: Compile and check for errors

Click the Compile Streaming Project (F7) button to check for errors.

compile for error

Note: You will get a compiler warning about the lack of a retention policy on the aggregate stream. You can ignore this warning. The reason for the warning is that windows default to KEEP ALL. If you explicitly state KEEP ALL, then the compiler accepts that you meant it. If you omit an explicit KEEP policy, the compiler warns you in case it’s not what you intended. Here, this is an aggregation where you are grouping by Machine ID - and you do indeed want to keep the aggregate value for every machine ID.

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