Group by performance in Qlik Sense & QlikView with order by sorting

When asked how to aggregate data in Qlik products in the quickest way, the answer is “it depends”. While the key factor is the uniqueness/ cardinality of the aggregating dimensions, there are other elements at play.

In general, though, the fastest way to aggregate in the data load script (after loading the data into memory) is:

  1. When aggregating by a low cardinality dimension in a small data set, resident load and run a group by immediately (this is also the fewest lines of script)
  2. When aggregating by a higher cardinality dimension, or on one that requires a lot of sorting prior to aggregation, resident load and sort the table by the high cardinality dimension as the first step. Then resident load this table and run your group by as a second step.

The short version: use approach 2 as the default, unless your data is very simple.

For Dimension1 (low cardinality), a direct group by (G) was fastest. For Dimension3 (high cardinality) and Number (low cardinality) an order by, then group by (O&G) was fastest by a large margin
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Task Chaining in Qlik Sense Enterprise SaaS

Today, QSE SaaS doesn’t do task chaining. Instead you have two options:

  1. Use a scheduled reload task for every app, and try to make sure the start time for task 2 will always be later than task 1
  2. Use Qlik SaaS REST APIs to trigger the reload

This post covers a simple approach (i.e. Qlik script only) for triggering reloads of downstream apps on completion of an app reload in a way that doesn’t require much maintenance or any external systems or integrations.

With the APIs, we can reload as frequently as we wish – to some disastrous results. Be careful.
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Qlik Sense Object Type Mapping

When you’re troubleshooting or diving into logs, it’s useful to have a mapping of object types. The name of an object is defined by the developer of that object, so there tends to be little convention – other some basic syntax rules and that Qlik Sense only allows one instance of the name per site.

Each object definition references the object type (qType)

Knowing what each type means is useful when inventorying a site for upgrade or migration.

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Check a Windows Service, if it’s not running, start it via batch script

Following a system restart, an overnight shutdown or a system update, some Windows services don’t always come up successfully. This script runs via Windows Task Scheduler and accepts one or more service names.

Log files are produced when a service is found to not be running (updated 16/05)

If the service isn’t running, it attempts to start it – and produces a log file to capture the incident.

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An updated Version Control tab for Qlik Sense & QlikView

This updated snippet (see original post from 2018) is available on GitHub, and included in this post.

The main benefits of this script are that it requires a single row addition per log, with no manual increment of the version number, and the version control information can be surfaced by the engine either to the UI or via the APIs.

This assumes a HidePrefix of %.

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Qlik Sense Release Version & Support List

Qlik Sense log files usually contain a reference to a build or engine number, and I’ve not yet found a complete list – so I’ve created one.

This list contains the current (at time of writing) list of Qlik Sense external version names to build number, release dates and end of support dates.

For the latest version of this list (and in CSV format), visit https://github.com/withdave/qlik-releases

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