Assigning Persistent Global Variables from Table Group Row Data, use in Aggregation calculation

Hi, 
 
I am trying to perform some aggregate calculations on a data set based on a field value that is grouped on in a simple table. I want the aggregate calculations to be performed for each grouping, but against the entire data set, and not just the data within each group. The way I thought to do this was to assign a persistent global variable via script using 'reportContext'. 
 
Reading the <a class='bbc_url' href='http://www.eclipse.org/birt/phoenix/deploy/reportScripting.php'>documentation</a> on report scripting, and also referring to this <a class='bbc_url' href='http://www.scribd.com/doc/2685017/BIRT-Advanced-Scripting-EclipseCon-2008'>this</a> powerpoint from EclipseCon that has some useful info on event triggering order for writing event handlers in javascript, I would expect to be able to do the following: 
 
1. Set the persistent global variable in the 'onCreate' event for the Table Group as follows: 
<pre class='_prettyXprint _lang-auto _linenums:0'>reportContext.setPersistentGlobalVariable("globalVar",this.getRowData().getColumnValue('groupedDateField'))</pre>
 
2. Retrieve the global variable in my aggregation calculation to use in the Filter Condition expression for an aggregation that I placed in the group footer. In 'Filter Condition', I do a check of the following: 
<pre class='_prettyXprint _lang-auto _linenums:0'>reportContext.getPersistentGlobalVariable("globalVar") != null</pre>
 
However 'globalVar' always shows up as null in the filter condition, and I can't use it to filter the data set rows on which I'd like the aggregation to process. 
 
I also did some testing/debugging to figure out what was going on where I tried to set the global variable in the 'onCreate' event handler of a regular detail row of my table (ie not the Table Group 'onCreate' event) via the same code as above, and then display the value of the global variable in a data element in a cell in the same detail row via the same expression used in my filter: 
 
<pre class='_prettyXprint _lang-auto _linenums:0'>reportContext.getPersistentGlobalVariable("globalVar");</pre> 
 
What happens in this case is that on the first detail row in my table the expression evaluates to null and the cell is blank, but in the second row, the cell does in fact display the value of 'globalVar', however it is assigned to the value of the 'groupedDateField' from the previous row in the data set. 
 
So, it looks like the order the 'onCreate' events are fired means that you can't access row data to set a global variable and then display the value of the variable within the same row? There appears to be a one row delay where the variable is set after the row is read and displayed. The documentation seemed to indicate otherwise from what I could tell, but event order firing is sort of a confusing concept to understand and the documentation isn't very thorough in explaining it (at least the documentation I've found so far). 
 
Any suggestions for how to do this or whether or not the behavior I'm seeing is correct would be very much appreciated! 
 
Thank you.

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Comments

mwilliams

If I'm understanding correctly, there is an issue with using an aggregation value in a filter or in sorting, so this MAY have something to do with it, I'm not certain. It would be nice to see the issue that you're having, so if you could recreate the issue with the sample database and attach the report in here, that'd be very helpful.

mwengren

Hi Micheal,

Thanks for the response. The attached report basically recreates my issue with the SampleDB. I have two aggregations in the table, both of which try to retrieve the persistent global variable in their Filter Condition expressions that I try to set in the 'onCreate' event handler of the detail row (I tried both the detail row and the group 'onCreate' event handler and get the same result). One aggregation I have in a column in the detail row, the other is in the group footer. It looks like in both they are getting null when trying to retrieve the value of the global variable I set. Also, I put a debugging column in the table called 'globalVar current value' that shows its current value obtained via the same code used in the aggregations. You can see how it is set to the value of the 'COUNTRY' column from the previous row, and not the current one.

And I'm not clear why the filter condition for the aggregations I put in the detail rows doesn't seem to be retrieving the value of 'globalVar' when my debugging output shows non-null values.

As far as the aggregations go, I realize I could do a count based on the group and not the table, but I need to calculate the aggregation against the full table for the actual data I am working with on my project.

Thanks!

Micah

mwilliams

It doesn't seem that the value is assigned to the variable soon enough to use in the aggregation. What is the calculation you're trying to do of the current group or row in comparison with the entire table data? Maybe I can help suggest another way to achieve the correct end result.

mwengren

Hi Michael, 
 
I was sort of afraid of that... not being able to use the variable value in the aggregation calculation. But, I don't see why I can't assign the value in the onCreate event handler for the detail row and then retrieve it in another cell within the same row. This seems like it should be supported in BIRT. In the attached report, it's clear the variable value is retrieved before it is set on a row-by-row basis, and that's why the output values in my debug column correspond to the 'COUNTRY' value for the previous detail row in the table. 
 
I hope there's a solution for how to do this, because I think in order to be able to do the sorts of calculations we need to do with our data, we need to be able to use the value of a grouped-on field in an aggregation across our entire dataset. This is actually a follow up post to an earlier thread I started that you were helping me with: 
 
<a class='bbc_url' href='http://www.birt-exchange.org/org/forum/index.php/topic/22179-aggregation-calculation-in-groups-using-a-grouped-on-value-for-a-table-aggregation/page__s__e0154abfb270e214048fbd413416a469'>http://www.birt-exchange.org/org/forum/index.php/topic/22179-aggregation-calculation-in-groups-using-a-grouped-on-value-for-a-table-aggregation/page__s__e0154abfb270e214048fbd413416a469</a> 
 
I'm still looking for a solution to my original date grouping problem... hoping to get some insight on the event firing order and how to write an event handler script that will be able to assign the global variable value somehow before the aggregation is processed. If I can't get that to work, I'm out of ideas for the moment. 
 
Thanks again, 
 
Micah

mwengren

Hi Michael, 
 
Do you know if there is an updated version of the ROM scripting guide? This looks like the most useful documentation available to help me figure out what to do to solve my problem, but it appears to be out of date with the latest BIRT releases and changes to the report phase system used by BIRT, and also functions like Total etc that are deprecated. It's really thorough, but unfortunately a lot of the info doesn't relate to current BIRT versions. 
 
This is the doc I'm referring to: <a class='bbc_url' href='http://www.eclipse.org/birt/phoenix/ref/ROM_Scripting_SPEC.pdf'>http://www.eclipse.org/birt/phoenix/ref/ROM_Scripting_SPEC.pdf</a> 
 
Thanks, 
Micah

mwilliams

This is the newest I see for Eclipse BIRT

http://www.birt-exchange.com/be/documentation/BIRT_231/EngineJavadoc/model/api/index.html