Tag: qlikview

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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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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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Comparing Autonumber, Autonumberhash128, Autonumberhash256, Hash128, Hash160 and Hash256 outputs in Qlik Sense and QlikView

There’s often a discussion about what each of these autonumber/hash functions does in Qlik. We commonly see these functions used for creating integer key fields, anonymising data (for example, names in demo apps), and maintaining long string fields for later comparison (as the hashes are shorter than the strings they replace).

Sample outputs from the random number generator, with all the functions present

To do this, I’m using the script below. I’m also keen to show outputs from QlikView vs Qlik Sense, and results of running the same script on another machine.

My observations are the following:
– AutoNumber/AutoNumberHash128/256 – different output per load as the value is typically based on the load order of the source data
– Hash128/160/256 – the same output, across every load. Stays the same between Qlik Sense and QlikView, and also between different machines

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Qlik load performance with RecNo() and RowNo()

Using RecNo() or RowNo() will impart a performance impact on your load script. I discussed these functions in a previous post where I looked at the output of RecNo vs RowNo.

I recently spotted an unexpected slow-down in a load script, which was caused by using one of these functions. In summary:
– Using RowNo() in a simple load script is considerably slower than RecNo()
– If you must use RecNo(), it may be faster to do this in a direct load
– If you must use RowNo(), it may be faster to do this in a resident load

Example script for one of the tests – load data from disk and add the RowNo

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Qlik Counter Functions and their outputs – RecNo() and RowNo()

In this post I explore the outputs of RecNo() and RowNo() to demonstrate the difference visually.

These two fields are often used interchangeably, but they provide different output. In summary:
– RecNo() is a record number based on source table(s)
– RowNo() is a record number based on the resulting table

As a result, RowNo will always provide a unique integer per row in an output table, while RecNo is only guaranteed to be unique when a single source is loaded (RecNo is based on each single source table, interpreted individually rather than collectively).

A snapshot of the test output

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Passing variables to applications via the QlikView QMC with Script Parameters and Publisher

Following this post which talks about methods for configuring apps, this post looks at how to achieve this via the QMC in QlikView and set variables in reloaded QVWs.

You’ll need to have Publisher enabled to access the features used for this example.

In a QlikView deployment with Publisher you’ll have access to the Reload tab for a task. This includes the option to add Script Parameters, which essentially leads to duplicate apps based on the provided field or variable name.

However – provide just one variable value, and you’ll pass this into one copy of the app.

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Version sheets and tabs in the load script for Qlik Sense and QlikView

In the absence of a source control system like SVN or GIT, a quick and easy way of capturing changes in a app is to update a version control tab before passing the app back to other developers, or onto testers.

This is a very low-tech solution, but the format below works well in shared environments. The first two tabs of your application should be:
– Version (explain the app and list changes you’ve made)
– Config (set the configuration values like paths, dates, etc used in your application’s data load and UI)

Version and Config sheets will become a familiar sight
Version and Config sheets should become a familiar sight

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