Vizlib Writeback : how to generate Unique ID for a line

[maxime_gerard]

Hello,

I'm using Vizlibwriteback to input data in Qlik Sense.
Between my front end table and my table in the database, I have a key : EntryRef.
When I add a row in my front end, I need the entry ref column to be automatically filled with a unique entry ref.

What I tried :

- Add a default values in the properties with the expression : =max({1} EntryRef)+1
Issue : The expression is evaluated based on EntryRef in my data model. If I add 2 rows without saving in between, the first row takes a value but it's not saved yet in the data model (because not reloaded yet) and the second row takes the same value as the first one.

- Add a default values in the properties with the expression : =round(num(now())*24*60*60) to get a different id every second.

Issue: it looks like the refresh frequency of vizlib is very low... When I add multiple rows, it displays the same ID, like if the now() function was not evaluated at the moment I add the row.

- Leave the EntryRef column empty in the front end and make a Identity field in the database so that it generates a unique ID in the DB.

Issue, the target table is a temporal table (to track changes). It's apparently not allowed to have Identity field in a temporal table.

Any Idea?

Thanks!

[JordyWegman]

Hey Maxime,

I don't have Writeback up and running now, but why don't you change the calculation to:

max( Total Expression1) + RowNo()

 

By using RowNo() and Total you can update the next rows.

Jordy

Climber

[maxime_gerard]

Hello Jordy,

Thanks for the reply!
Unfortunately, your expression is evaluated on data in your data model. In vizlib, when you press the button "Add row", it adds a row in your front end vizlib table, but it doesn't reload your app until you press the "save" button. When "save" is pressed, a partial reload is performed and the added row is inserted in your data model.

So, if I add 2 rows without pressing the "save" button, the expression will be evaluate on the same dataset and both rows will have 902 (if I take the data in your screenshot) as value.

In vizlib the is 3 column type : "Dimension", "Measure" and "Column". If I use a measure, it's related to my in memory data so it doesn't work. If I use a Calculated column, functions like rowno() are returning 1 on every line...