What is the best way to populate a dropdown ?

Your snippet should look more like

 

a!dropdownField(
    label: "Manager",
    labelPosition: "ADJACENT",
    placeholderLabel: "--- Select a Manager ---",
    choiceLabels:{index(local!managers.data, "name", {})},
    choiceValues:{index(local!managers.data, "id", {})},
    value: index(ri!manager, "id", null),
    saveInto: ri!manager.id,
    validations: {}
)

 

If your query doesn't take too much time, loading the managers in a load() variable on the interface will be fine. However, this load variable will re-evaluate whenever the user opens up the interface, so if you anticipate both the user frequently leaving/coming back to the form AND the query is slow, I would store the data in process and pass the list in as a rule input.

Your snippet should look more like

 

a!dropdownField(
    label: "Manager",
    labelPosition: "ADJACENT",
    placeholderLabel: "--- Select a Manager ---",
    choiceLabels:{index(local!managers.data, "name", {})},
    choiceValues:{index(local!managers.data, "id", {})},
    value: index(ri!manager, "id", null),
    saveInto: ri!manager.id,
    validations: {}
)

 

If your query doesn't take too much time, loading the managers in a load() variable on the interface will be fine. However, this load variable will re-evaluate whenever the user opens up the interface, so if you anticipate both the user frequently leaving/coming back to the form AND the query is slow, I would store the data in process and pass the list in as a rule input.

Thanks for the reply

choiceValues:{index(local!managers.data, "id", {})},
If i give like this , i am getting the error below

A dropdown component [label=“Manager”] has an invalid value for “choiceValues”. Choice values cannot be null.

This error indicates that an id in your list is null. While the "value" of a dropdown can be null, none of your "choiceValues" can be null.

Assuming the "id" is a primary key of your manager table, I wouldn't expect any of your ids to be null. I would look into the data being returned.

Oops Yes , i forgot to return the id in the rule :)

> I would store the data in process and pass the list in as a rule input.

Is it a good practice to keep long lists in process variables? It will consume Appian memory. Practically I don't think there would be a very long manager list. In case it is it would be easier to select department first with less managers inside.

The exact approach depends on the use case. The recommendation was made to improve user experience if the query to retrieve the managers was slow.

I don't think extracting two columns for 1000 records will take much longer than for 10. If everything is OK on the database side, not a heavy view, etc.

And if the size of the data is an issue it is not good to cache it in each process.

Again, the exact approach depends on the use case. While I generally agree there would not be a difference between querying 10 records vs. 1000, this is not a guarantee.

The same goes for caching data in process, there is a trade-off here between process memory and user experience. You can easily reduce process memory by marking the process variable as hidden and update your archive settings to quickly archive the process.

as per the use case , This drop down should grow at max 100 - 200 values. is it a better idea to convert to a grid ?

I would use a grid or a picker. You can refer to docs.appian.com/.../Appian_Style_Guide_for_Interface_Designers.pdf for recommendations on what components to use based on the size of your reference data.