Qlik Sense On Demand apps

About a year ago, I took a first look at Qlik Sense on demand app generation for a customer. Their problem was not really using big data, but rather that the data the needed for some analysis was simply too big to handle in a Qlik Sense ( or QlikView) app. They had to limit the data to just a shorter time period to make it run at all. Our conclusion at the time was that On Demand App Generation might be the right the right tool, but we had to prioritize other projects and did not complete the project.

Now, about a year later, we have the time to look into it again. And while I think the core concepts and functionality is the same, it has had a facelift, and feels much more like a product ready for production.

Improved user interface

The on demand app generation feature consists of a master or selection app and multiple on-demand apps. The user uses the the selection app, which contains aggregated data, to select a subset of the total data. He then generates an on-demand app, with detailed information about that subset.

The interface for this has been improved a lot. Previously keeping track of your on-demand apps was difficult, now you can find them in the selection app.

All your generated apps are listed in the popup for the selection app, together with information about when they where created and the selections they are based on in the selection app. You can also manage your generated app here, delete it when you are ready with it, reload it with the same selections but new data and open it.

Loading data into the on demand app

In many respects developing on demand apps is just like developing any Qlik Sense app. That’s part of the strength of the feature – you can use your Qlik Sense knowledge for on demand apps too, visualizations are the same, much of the load script will also be the same. What’s new is the connection between the selection app and the on demand app: how do you get the users selections into the ODA, and how should you write the load script.

When we worked with this a year ago, we used Qlik Sense varibles and the script snippets published in Qlik Sense help around using the variables to generate script statements. These snippets helps you generate selection queries in the form of SQL SELECT’s to fetch the data. Our use case is somewhat different: our problem is that we have internally generated data that is simply to big for one app, but the data is not in an SQL database (even if the original source is a database), but in QVD files. This makes it possible to use a much easier method: we can have the selected values inserted into inline tables, and then use them in ordinary LOAD statements.

Using an inline table with the selected values

The first step is to create the inline table:

selected_item_tab:
LOAD * INLINE [
 SELECTED_ITEM
 $(odso_ITEMID){"quote": "", "delimiter": ""} 
];

Item ID’s for all selected and optional items will then be injected into the script. By using prefix ‘odso’ we allow the user to make selections on any level in the ITEM dimension, like product groups etc.

You can then use the inline table when you load your actual data:

LOAD
  ITEM_ID,
  ...
FROM .....qvd (qvd)
WHERE EXISTS(SELECTED_ITEM,ITEM_ID);

This will filter the data so that only selected items are included. You can also combine several dimensions, like time or geography to further reduce the data. No variables or string parsing is needed. So far this seems to work well.

Getting used to the generated apps

Perhaps the most difficult part of the On Demand app generation remains. The generated apps will only select a subset of the data, and in some cases it won’t be obvious what the subset is. Qlik users are not really used to this. Selections will be a two-step process, where the actual analysis will work as we are used too, but the initial selection cannot be immediately changed. This is a new way of working for users. Also totals calculated in the generated app might be useful for reference, it must always be remembered that they are just for a subset. We will try to make the initial selections clearly visible to the user of the generated app, and perhaps we should also try to bring over some summarys etc for the complete data, but still users will have to think differently. That might be the real challenge with this.

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