Wait for widget user input before filtering delta lake

[matjohvolvo]

Hello,

I am new to using Knime and I am attempting to develop a user interface that will enable our team to extract data from our delta lake with ease.

The database connection is directly linked to a Databricks environment, which means that any major computations will be performed on a separate cluster rather than within Knime. My goal is to create a streamlined approach for filtering requests to the delta lake based on three user-selected conditions that are available in three dropdown menus, such as the Value Selection Widget.

The selection process is hierarchical, meaning that selecting Parameter1 will subsequently filter Parameters2 and 3. In turn, selecting Parameter2 will filter Parameter3 but not Parameter1, and so on. Ultimately, I would like to implement a “refresh” button that utilizes these parameters to filter the entire delta lake. The filtering of the data lake will be used with pyspark code / Spark row filters where the parameters will be used as Flow variables.

However, I am currently facing a basic problem. I am unsure how to create a component that waits for the user to specify the parameters in a particular order before pressing the “Refresh/Execute/Whatever” button to filter the delta lake. Additionally, I am seeking guidance on where to find helpful resources for this task.

Unfortunately, I do not yet have a clear flowchart for this process to present. However, I hope that my intentions are somewhat clear.

Thank you for your assistance.

[julian.bunzel]

Hi @matjohvolvo,

Welcome to the KNIME forum.
I am currently building an example and will get back by tomorrow.

Best regards,
Julian

[julian.bunzel]

Hi,

Really sorry for the late response but I hope it is still helpful.
I was able to come up with a solution.
I have created a component that contains a Single Selection Widget and which allows you to define an invalid default (i.e., Please select…). You can also define the level (i.e., level 0 for the very first set of options) as well as whether a component refers to the last level (if so, the automatic re-execution is disabled). You can chain them in a row to filter the possible choices in the next selection but it also works with just one of these components to then be able to distinguish between a valid and an invalid value because of the invalid default value.
Here is an example:

I hope this helps.
If there are any questions let me know.

Best regards,
Julian

[matjohvolvo]

Thank you so much for your effort! This is exactly what i was looking for. I will try this out